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by 1930 the search for The elusive 9th Planet had been running for well over three decades since the turn of the 20th century precise observations of the orbits of Uranus and Neptune had suggested that there was something else lurking in the darkness of the outer solar system another distant World far beyond Neptune but hunting down such a faint object was like looking for a needle in the celestial Hast stack leading the search for Planet X over
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much at this time was the founder of the flag staff Observatory peral LEL starting in 1906 LEL had embarked on an obsessive pursuit of the ninth planet but despite years of work he would not live long enough to see its Discovery and he would never know how close he came to finding it himself unknown to LEL an image of Planet X had been captured in two photographs he had taken just a year or so before his death in 1916 but the evidence was missed the photographic plates were
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filed away and the search would go on without him for another 15 years the logic behind using identical pairs of photographs taken a few nights apart was simple by examining the two images for any stars that appeared to have shifted position they would be able to differentiate between the distant stars in the background and anything that was orbiting closer to Earth hundreds of pairs of images were taken at the lower Observatory for this purpose and analyzed using a blink
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comparator which helped to reveal any minute differences between the images but it wasn't until the night of the 29th of January 1930 that Tombo would strike gold comparing the two images he had taken a week apart Tombo discovered what appeared to be a moving object on the two plates across those few days a dim spot had moved no more than an inch but that movement signified something profound this was an object much closer to the Earth than the distant stars in the background
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an object that had moved as our perspective had changed with the Earth's Own orbit and over the course of that week this object appeared to have shifted against the distant background tombor had found Planet X which would be named Pluto after the suggestion of Venicia Bernie an 11-year-old English school girl from Oxford with an interest in classical mythology taking off from Cape canaval Air Force Base on the back of an atlas 5 rocket the New Horizon space probe
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began its epic journey across the solar system towards Pluto in January 2006 just 9 years after the death of Clyde Tombo this tiny interplanetary probe no bigger than a grand piano made room in its payload for 30 G of his ashes a tribute to the man who had begun our journey to Pluto 76 years before for Alan Stern principal investigator of the New Horizon's Mission this this move fulfilled a promise made to Tombo shortly before New Horizons became a project while we were still
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trying to get funding to fly a spacecraft to explore Pluto Clyde died in January of 1997 and prior to that he had asked if a mission ever did get launched if there was a way it could be considered if some of his ashes could be sent on the journey and I had heard about that back in the '90s and when it came close to launching New Horizons in the summer of 2005 I reached out to his family to see if that's something they wanted and it was still possible and it was and we found
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a way to do it and we were very proud to be able to make it happen not just for Clyde tombor and his family but even more so for the people of Earth because it makes a very human connection between the discoverer of this world and those who were the explorers of it on the New Horizons team Le the Earth with an escape velocity of 16.26% New Horizons was the fastest probe ever launched from
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our planet reaching Jupiter in just over a year it progressed on its way with a gravity assisted kick from the gas giant sending it hurtling across space with all non-essential systems shut down to conserve energy this little probe would sleep through most of its epic 8-year Voyage in the dark after 20 years of planning building and dreaming the New Horizon's team could only wait and hope
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for its safe passage as it made its way towards the last unexplored world in our solar system but while the voyage itself proceeded without a glitch back on Earth the status of the mission was about to take the most unexpected of turns starting with the discovery of the rocky object 15760 albian back in 1992 the description of Pluto as a planet orbiting alone in the farthest reaches of the solar system would come under increasing scrutiny Pluto it seemed was not so lonely after
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all this was a region of space filled with an array of orbiting objects and as we began to peer into the Kyper belt we discovered they were far from just fragments this was a region of space filled with Pluto likee worlds 50000 quaa an object half the size of Pluto discovered at the Palomar observatory in June 2002 90377 sedna a large minor planet discovered in November 2003 on an 11,400 year orbit around the sun 1361 98 haa a huge pebbl shaped world with two tiny moons in
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orbit discovered in December 2004 136 472 mar mar a dwarf planet perhaps 2/3 as big as Pluto discovered in 2005 then in January 2005 we spotted 1361 99 Eris a world almost the same size as Pluto itself if not bigger these discoveries and the hundreds we've made since forc the international astronomical Union the ruling body on Earth for all things astronomical to formally reconsider the definition of a planet in October 2006 they published a set of three criteria that any object
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in our solar system would have to fulfill if it wanted to stake a claim of planethood one it has to orbit the sun two it has to be massive enough for it to form a sphere under its own gravity three it has to be massive enough to clear its own orbit of any other objects dust or debris Pluto certainly ticks the first box completing an orbit of the Sun every 248 years we also know even from our most distant observations that Pluto is nearly perfectly spherical and so the
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second Criterion is also a clear tick for Pluto but when it comes to the third requirement Pluto is not so lucky it is simply not massive enough to blow away all the bits of dust and ay in its orbit and for that reason it fails to make the cut as a planet since September 2006 Pluto has been officially designated a dwarf or minor planet a sphere orbiting the Sun yes but a planet no the third Criterion is ultimately the one that necessarily separates the chosen eight
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Mercury Venus Earth Mars Jupiter Saturn Uranus and Neptune from the rest of the globes that orbit the Sun because if Pluto was a planet so too would be sna Aris makak and all the other tens or potentially even hundreds of smaller objects that orbit in the distant Kyper belt billions of kilometers from the Sun so for now at least we have a solar system filled with eight planets but many worlds hundreds of moons and dwarf planets many that remain unknown
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and out there waiting to be discovered as for Pluto despite the best efforts of complaint and protest around the world by the time New Horizons entered the final leg of its epic Voyage it had changed from a mission of Planetary Exploration to the first ever mission to a dwarf planet in the Kyper belt thankfully our solar system pays little heed to the fanciful definitions of humans from the international astronomical Union and while downgraded by name the world that awaited
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us was anything but a disappointment after nearly 10 years alone in the icy darkness of space New Horizons awoke from its state of hibernation and the pixels that Hubble had seen all those years before were at last replaced by our first glimpse of the most distant world we have ever visited in July 2015 New Horizons began to beam back images from its close encounter to reveal Pluto not as a
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frigid featureless Frozen Rock but something far more beguiling planet or not Pluto was beautiful the images revealed a complexity of character stretching across its freezing minus 230° C Surface that contained all the features of a dynamic active world the blemishes we gazed at from a distance were no longer just smudges but high definition images revealing an extraordinary range of geological form and structure New Horizons first spotted Pluto shortly after
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launch just a dot in the distance and year by year that dot grew a little brighter but even after 9 years of flight it was only two pixels across and we were only 10 weeks from arrival when the blurry images were as good as the Hubble had been able to do all that time but then they got a little better and a little better and a little better and suddenly overnight as we flew past it went from a kind of naked eye vision of what the moon looks like where you can see
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the general patterns of bright and darkness to all of a sudden this phenomenally complex world with mountain ranges and gorges and Glaciers and an atmosphere glowing up to half a million feet in the sky and polar caps evidence for a liquid Ocean on the inside five spectacular moons and so much more it was almost overwhelming in the first days and weeks after to see what an amazing Place Pluto was and I took to saying that the solar system had saved the best for last Alan Stern
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New Horizon's Mission this was a landscape built from Frozen nitrogen with soaring mountains and complex rided terrain with a look of snake skin but one feature more than any other leapt from the images New Horizons fed back to us running across the equatorial region of the planet we could see a giant heart-shaped plane of Frozen night nitrogen methane and carbon monoxide that stretched for a million square kilom a region that has been named Tombo Regio or to give it
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its more popular name Pluto's heart the Western lobe of the heart is called Sputnik plena and at its eastern Edge lies a range of mountains made of pure frozen water ice that rises miles above the Frozen plain but it wasn't just the soaring mountains and romantic form of this region that caught the eye there was something else about Sputnik plena a strange detail that set it apart from the rest of the dwarf planet everywhere we looked across the surface of Pluto we saw a world
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covered in craters the scars of impacts that just like on the surface of our moon have taken place over billions of years except on Sputnik plantia this icy plane appeared unblemished an utterly smooth Smo surface untouched for mile upon mile without a single crater to be seen and the closer we looked at this region The Stranger it appeared because as we studied the detailed imagery beamed back by New Horizons we saw a puzzling set of patterns and shapes across its
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surface a series of hexagons and pentagons crisscrossing the Frozen nitrogen exterior that suggested something intriguing was going on beneath New Horizons had provided us with a hint that Pluto's heart was beating the geometric patterns we see on the surface of Sputnik plena may be distant but they are remarkably familiar we see these patterns all across nature from the surface of the Sun to a pot of boiling water they are the characteristic patterns of convection the
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forms we see when a heat Source causes material to rise up and then fall back down again as it cools so it seems that underneath the surface of this region of Pluto there is a heat source which is creating a circulating convection current melting the nitrogen ice and causing it to rise cool and then Fall Again constantly resurfacing the area removing any scars from impacts and leaving the characteristic cells of convection behind we don't know for certain where the heat is coming
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from that has shaped this distant world but many scientists now believe that below the surface of the glacia there was once a liquid body of water a flowing ocean that might even still be there it's this ocean that could possibly explain the strange patterns on the surface because it needs only a small difference in temperature between the underground ocean and the Frozen nitrogen above to create the convection currents needed to produce the crater free pattern plane we see
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today just imagine that billions of miles away from the sun on the Frozen Frontier of the outer solar system there may still be an ocean of water and what is above this lonely distant ocean as New Horizons left Pluto behind to continue its lonely Voyage out into the darkness NASA turned its camera back towards the dwarf planet revealing a hazy atmosphere made mostly of nitrogen a blue sky above an ocean of water 4.8 billion kilm from Earth
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today New Horizons just like Voyager 2 continues onwards heading out into the furthest reaches of our solar system in January 2019 3 and 1 half years after leaving the Beating Heart of Pluto behind it revealed a new world the first image of 2014 mu69 otherwise known as Ultima Tula the Snowman dwarf planet by visiting these outer worlds we have momentarily illuminated the darkness found and explored worlds far beyond our imagination and opened a new and
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as yet unfinished chapter in the story of our solar system it's a story that began with the formation of an ordinary star a little less than 5 billion years ago a star that would leave just the right ingredients for eight planets and countless worlds to form in her Shadow Jupiter came came first the Godfather that would cast its hand across all that was to follow shaping the destiny of the solar system as it wandered near and far in Mars it would leave a
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world too small to fulfill its potential chasing the destiny of its nearest sibling before rapidly slowing down Venus would soon follow and Oasis in its earliest of days choked by the intensifying grip of its atmosphere just like Mercury it would find find itself too close to the Sun to hold on to its chants only one planet our own has held on to its oceans beneath the thinnest of veils
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a world that through the luck of its formation has not only sparked life but nurtured it as well for 4 billion years our planet has remained stable long enough to allow the most curious of Minds to evolve look up and explore this is our story a story that we now know not only has a beginning and a middle but an end too an end that we'll see the islands of life in our solar system shift from
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one world to another until perhaps in the Final Days of Our Star it will be Saturn that Harbors a world where a life form can call it a home we've written this story not with imagination but with exploration a story just like the very greatest of our legends that will be added to and heightened as it is passed down the generations to come where it will end up I do not know lost with our planet or carried onwards to Distant Worlds its Destiny and our destiny are unmistakably
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entwined why do we explore some people ask shouldn't we focus on solving our problems here on Earth before spending time and energy and resources reaching for the Stars well I think that focusing entirely on our Mo of dust would be a profound mistake it would mean that we've taken the decision to sit huddled in a tiny corner of the solar system wondering what we're doing here it would mean that we've taken the decision to fight among ourselves for
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ever more precious resources confined below a thin shell of air to the two-dimensional surface of a small rock rather than following the three-dimensional path marked out by the lights in the night we need to shift our Focus we live in a solar system of Wonders of planets of Storms and moons of ice of Landscapes and Vistas that stir the imagination and enrich the soul a system of Limitless resources Limitless Beauty and Limitless potential if
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we don't go there we'll never go anywhere and if we go nowhere then we'll have no future at all to the Romans Jupiter was the king of the Gods the ruler of the heavens and a figure of power who drove forward the allc Conquering Roman army with a thunderbolt in one hand and an eagle by his side the name Jupiter itself means Sky father and it's constructed from the Latin words Diaz day or sky and part farther and as is often the case with mythology there is
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a truth lurking amongst the legend in size alone Jupiter is by far the biggest planet in the solar system its mass is a staggering 1,900 trillion trillion kilg that's 2 and 1 half times bigger than all of the other planets in our solar system combined it's so big in fact that if you were an alien species observing our system from a distant part of the Galaxy the Sun and Jupiter might well be all you could see with a diameter of 142,5 184 km at the Jovian Equator the Earth would
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fit inside Jupiter over 1,300 times and yet this giant of a planet is made almost entirely of gas comprising 89% hydrogen and 10% helium it is far less condensed than any of the rocky planets and has a density far smaller than that of the earth 1326 G per cubic cm compared with Earth's 5513 G per cubic cm for all of its size Jupiter also has the shortest day of any Planet completing a single rotation every 9 hours 55 minutes and 30 seconds as it whips around on its axis at 45,000
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km an hour in the last 50 years our knowledge of Jupiter has grown exponentially and with it we've gained a deeper understanding of the role it has played in the shaping of the solar system no longer just the beautiful banded world we see through our telescopes this is a planet that we have explored up close our eyes and ears living within the Jovian system for years at a time the first close-up glimpse of the giant planet came with the cameras of the pioneer 10 spacecraft in
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1973 this was the first of our planetary Explorers to cross the great boundary of the asteroid belt and from an approach of just over 130,000 kilm it was able to take close-up images in total Pioneer 10 sent back over 500 precious pictures of this distant world before flying onto the very edges of the solar system to complete its Mission just over a year later Pioneer 11 followed hot on the heels
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of its sibling craft and swept within 43,000 km of Jupiter's Cloud tops before heading on towards Saturn Voyager 1 and two passed by Jupiter in the late 1970s taking the first extraordinary images of not just the planet but its moons too as part of their own grand tour of the solar system this was an historic moment as Fran banel scientist on The New Horizons Mission explains we had hints but
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it wasn't until Voyager went up close and personal and took amazing pictures of the moons of the planet that that we really began to get a sense of just how complex the worlds around Jupiter are and what a variety there is the Galileo spacecraft became our first explorer to actually live in the Jovian system entering orbit around the planet on the 7th of December 1995 Galileo spent 2 years touring Jupiter and allowed us to explore as never before thanks to its audacious Deep dive
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directly into the planet a probe that was released from the craft collected data for almost an hour as it parachuted down through 150 km of Jupiter's atmosphere before it was destroyed by the intense pressure and temperature Galileo was also the first mission to explore the extraordinary moons of Jupiter in any detail helping us to see for the first time that Jupiter lies at the center of an extraordinary system with more natural satellites than any other planet holding 79
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moons in its orbit at the time of writing 12 of these satellites have been discovered since the beginning of 2017 it's almost certain that the number will rise in the coming years too as we're able to explore the Jovian system in even greater detail the vast majority of Jupiter's moons 63 are not much more than fragments of Rock None bigger than 10 km in diameter and are captured asteroids that now orbit the planet rather than the Sun but at the other end of the
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scale Jupiter has four giant moons fiery IO is the most volcanically active world in the solar system its surface littered with lakes of lava while I see Europa is at the Other Extreme with its frozen surface protecting a global ocean of water beneath marble ganim is Jupiter's largest satellite and the only Moon we know of that has its own magnetic field while Kalisto the outermost of Jupiter's Galilean moons is also thought to be home to a sub surface ocean each
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Moon has a unique intriguing character and they are all visible to us here on Earth using nothing more than a pair of binoculars then in August 2011 NASA launched its latest mission to Jupiter Juno after traveling for 5 years the spacecraft reached Jupiter in July 2016 and entered into a perilous elliptical orbit that took it from 8 million to just 4,000 k m above the cloud tops of Jupiter's
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surface Juno is a mission designed to probe for Jupiter's origin and evolution which it does by carrying instruments to measure the planet's composition and its magnetic and gravitational fields allowing it to build up a detailed picture of the Interior it also has the best camera we've ever pointed at Jupiter which since 2016 has been sending back the most incredible images of the giant planet ever taken we'll let Heidi Becker a jet propulsion laboratory physicist
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and the radiation monitoring investigation lead on the Juno Mission explain the detail of this incredible piece of technology the star tracker is an 18lb camera because it's passed with tungsten in order to keep the radiation out what Juno Cam's images have shown us is that Jupiter is like going to an impressionist Art Gallery it's seeing Jupiter and those atmospheric features up close with the highest resolution that's ever been achieved we're seeing the zones and belts
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the jet streams of Jupiter in more detail than ever before for all the majesty and wonder these probes have brought us Jupiter remains a vast distant planet sitting on average 588 million kilometers away from us here on Earth it's easy to think of this world as a benign Beauty a jewel to Marvel at but what makes Jupiter the true king of the heavens is not just its beauty but its influence over the unfolding story of the solar system as we've explored this world ever closer we
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are discovering that Jupiter's effect on the fates of entire planets is far more direct and violent than we ever imagined its massive gravitational field exerts control not just over its moons but also over every asteroid every world and every life force in the solar system whose Destinies it still holds in its vast reach to understand the awesome power of Jupiter we don't need a billion
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dollar spacecraft a rocket or even a telescope all we need to do is to look no further than the ground beneath our feet the surface of our planet is littered with the evidence of our distant Godfather's meddling written across our planet in the violent gravitational handiwork of Jupiter are at the most recent count 190 visible impact craters not to mention the thousands more that have long disappeared as the active geology of the Earth's surface has continually renewed
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itself one of the most famous is the meteor crater also known as the baringer crater in the northern Arizona desert which measures more than 1,000 M across and at its deepest point drops 100 M below the Crater Rim in the late 19 century geologists believed this vast feature had been created by the San Francisco volcanic field that lies just a handful of miles to the west but in 1903 Daniel baringer a mining entrepreneur and sometime hunting friend of Theodore Roosevelt
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began an extensive investigation of the crater and published a set of findings suggesting that it had not been created by a volcano but rather by a large incoming projectile from outer space this was the first time anyone had suggested such a theory and baringer backed it up with a host of geological evidence including the discovery of around 30 tons of large ion oxide fragments from the suspect meteorite at the time there was much skepticism that an incoming meteor could create
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such a massive geological feature but ignoring the overwhelming scientific consensus baringer put his money and reputation firmly where his mouth was and formed the standard iron Company the company was created with the sole aim of mining the crater for the 100 million tons of iron ore that baringer believed lay in the ground having been deposited by the incoming meteorite even at 1903 prices if he'd been right that amount of iron ore would have been worth over a billion
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dollars so unsurprisingly he continued to dig down to depths of over 400 m in his Pursuit Of The meteoric Remains unfortunately for baringer it would take him 27 years of mining to find out what we know today the meteorite that impacted in that Arizona desert was not only much smaller than he predicted with current measurements suggesting it was around 300,000 tons 300 times less than he
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had thought but also with the benefit of advanced studies in such impacts since then most of the nickel ion meteorite that fell was vaporized as it struck the ground at around 43,000 km hour barringer's money evaporated not quite as quickly as the meteorite but by 1929 operations at the site had stopped and most of his fortune had gone it would be 50 years before barringer's work would be fully and finally verified with a landmark publication in 1963 analyzed the similarities
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between the geology of the baringer site and the craters that had recently been created as a result of testing nuclear weapons in Nevada Shoemaker was able to show that the shocked courts also known as coite that was identified at Barringer Crater could only have been formed at the enormously High pressures and temperatures created by a nuclear explosion or in the case of the Arizona crater by the extraordinary impact dynamics of a 300,000 ton meteorite crashing into
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the ground we know now that the giant rock that created the crater like most of the meteorites that strike the Earth was once an asteroid just one of the millions of rocks that Circle the sun between the orbits of Mars and Jupiter most of these have been in a stable orbit for billions of years the rocky leftovers of the birth of the solar system they orbit in an eternal junkyard of planetary castoffs but occasionally one of these huge rocks is propelled towards the inner solar
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system and more often than not we think the nudge that causes it comes from Jupiter why this should happen and how Jupiter exerts its power not just over the asteroid belt but over all the worlds around our sun is a story we are only just beginning beginning to understand from our home here on Earth it's hard to imagine the vast reaches of space that extend beyond our little bubble and the huge expanse of time over which events in the cosmos play out but
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all the evidence suggests that around 4.5 billion years ago Jupiter's orbit began to change and as it did so it triggered a period of unprecedented violence during which the Young solar system was utterly transformed we know this because the marauding planet left a trail of Destruction in its wake that we've only just begun to explore as we've attempted to uncover the 5 billion year history of our solar system we've repeatedly looked to the eight planets and the moons that
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orbit them to provide clues that fill in the gaps in our story in the last 50 years dozens of missions have crossed our Thin Blue Line on the way to those worlds but only once have we sent a spacecraft to explore a very different type of world to search amongst the rubble of our solar systems earliest days and explore the handful of Worlds that never quite made it sometimes the answers lie in the gaps launched on the 27th of September 2007 the dawn space probe took off
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from Cape Canaveral on a mission to explore the two largest objects in the asteroid belt Vesta and the dwarf planet series this $450 million project was part of NASA's lowcost Discovery program one of a series of missions designed to be faster and cheaper to deliver but this was no beist mission for NASA equipped with the most advanced ion propulsion system ever used in outer space Dawn would be able to reach the asteroid belt and become the first craft in the history
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of human exploration to enter orbit around Siri and yet without a major planet in its itinerary the attention of the world only seemed to glance towards this Mission and for the most part its extraordinary findings slipped between the gaps of public attention the aim of the Dawn mission was simple this would be the first spacecraft to travel to the asteroid belt the first to orbit an object in this Uncharted region of the solar system and the first to visit a dwarf planet
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all in all this Mission profile was designed to allow scientists a rare chance to travel deep into the past and Glimpse the earliest moments in the origin of our solar system the mission allowed us to explore the evolution of Vesta and siries two very different objects Frozen in time for billions of years since they faltered and failed in the process of becoming fully-fledged planets to travel to the asteroid belt would be a slow but steady voyage for dawn after hitching
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a conven itional ride into space on the Delta 2 rocket the spaceship began firing its thrusters to orientate and Propel itself away from the earth and towards Mars the ion thrusters on Dawn were an efficient but gentle form of propulsion for the spacecraft taking 4 days at Full Throttle to accelerate the craft from 96 km per hour it's not exactly a sports car but when it comes to efficiency the ion propulsion system is difficult to beat powered by a 10 Kow solar array
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Dawn's engines ran for almost 6 years across the 11-year lifetime of the mission propelling the craft across space using less than 400 kg of its Xenon fuel supply while reaching speeds of 41360 KM hour its trajectory took it on a 16-month journey to Mars where a gravitational kick sented on its way out to the asteroid belt and onwards towards Vesta its first destination
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almost 500 million kilm from the Sun the asteroid belt lies halfway between Mars and Jupiter the boundary line between the four rocky worlds that orbit closest to the Sun and the Giant gas and Ice planets that lie Beyond made up of millions of pieces of rock from the dawn of the solar system it's a graveyard of failed planets remnants from the Heyday of planetary Construction we often imagine the asteroid belt to be a dense unnavigable mass of tumbling Rock but in reality
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it's something quite different the total mass of all those rocks is estimated to be 3 * 10 ^ 21 kg which although an enormous sounding number is just 4% of the mass of our moon with a third of that mass found just in the largest object series the rest of this Cosmic junkyard is made up of objects covering a vast range of different sizes on one end of the scale we think there are at least a couple of hundred asteroids larger than 100 kilometers in size then come a million or so
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stretching to at least 1 kilometer or more and a countless spread of smaller objects number in the millions and billions depending on how small you want to go all of this sounds like it should make for a crowded environment full of collisions the perfect location to form the basis of a computer game or disaster movie but even with that many objects the space they occupy is so unimaginably
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vast spread out across 13 trillion trillion cubic miles of space making the average distance between any two large asteroids approximately 2 million miles or 8 times the distance from the Earth to the Moon these distances are so large that when we send spacecraft to the outer solar system the chances of hitting anything are so small that the engineers don't need to make any course corrections to pass through in fact if you were standing on an asteroid you you'd be
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lucky to see another one and if you did it would appear as little more than a tiny point of light in the darkness as it traveled through this vast emptiness in the early summer of 2011 the dawn spacecraft slowly began to bring its first Target into view from a distance of over 1.2 million kilm Dawn took its first photograph of Vester against the backdrop of a thousand stars over the next two
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months dor homed in on Vesta chasing it across the vast reaches of space to arrive at this the second largest rock in the belt entering its orbit on the 16th of July 2011 Dawn became the first spacecraft to enter within the gravitational hold of an object in the asteroid belt and for the next 14 months it would explore this extraordinary ancient object providing a glimpse of our solar system in
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the very earliest days of its life when for Vester to give it its full name was first discovered by the German astronomer Heinrich alur in 1807 it was the fourth asteroid to be discovered after siries Palace and Juno hence the four in its formal designation alur was convinced he had found the remains of a Lost Planet destroyed in some long ago Collision even so just like the other three
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objects at first Vesta was given full planetary status bringing the number of classified planets in the solar system at that time to 11 it wasn't until 1845 nearly 40 years later that a flood of further discoveries began that quickly increased the number of objects in this region to a point where it was clear they couldn't be classified as planets and so in the 1850s 15 planets became eight and the classification of these objects as a different class of minor planet asteroids had
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begun 160 years later as Dawn began its year-long residency in the vicinity of Vesta it soon became apparent that alur's suggestion that this was a fragment of a long lost planet was not so far off Vesta is a spheroid shaped Rock 530 km in diameter and pot marked with impact craters the most striking example of these is the crater Rea Sylvia which at 500 km wide and 20 km deep is one of the
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largest impact craters in the solar system at its Center is a mountain that rises into the Blackness 22 km from the crater floor making it the second tallest peak in the solar system after Mars's Olympus Mons what's particularly extraordinary about this crater is that we've long suspected that a particular class of meteorite found on Earth known as HED meteorites actually come from material that was blown off the surface of Vesta when this impact occurred around a billion years
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or so ago using Dawn's instrumentation we were able to directly measure the GE ology of rocks in Rea syvia and when compared with the samples on Earth we were able to conclude that they are of the same origin in one of the most beautiful examples of geological analysis in the history of the subject we now know that we can hold a piece of this farway asteroid in our hands and directly analyze the secrets hidden within it when taken all together the H meteorites and
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the findings from the dawn spacecraft have enabled us to paint a detailed picture not just of Vesta today but also of its history dor has revealed to us that Vesta has a metal Rich core just like all of the terrestrial planets including Mercury Mars Venus and Earth and Analysis of its surface geology has enabled us to date the formation of the asteroid to a couple of million years after the first solid objects began to take shape in the solar system these are just two of the
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clues that point us to an extraordinary conclusion Vester is is perhaps the last remaining example of a protoplanet a half-formed world from the very earliest days of the solar system Frozen in time this is a stage that every world we know of passed through including the Earth Vester was on the way to becoming a planet almost 4.5 billion years ago but something happened to stop its progress while other worlds went on to flourish and other protoplanets disintegrated in the violent
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collisions of the early solar system Vesta somehow seemed to survive a fossil of planetary formation for us to not only look at but through a quirk of Fate actually hold but this was not the end of Dawn's dive into our deep history departing Vesta after 14 months of study Dawn fired its ion drive leaving the orbit and heading off for its second planetoid rendevu at the largest of all the asteroids series Dawn arrived at the dwarf planet series in early March 2015 and from
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the very first moments of its observations it sent back some astonishing images very little was known about series before our spaceship arrived but it soon became clear that this was a rock with far more of a story to tell than we could ever have imagined a story that would help reveal A New Perspective on the Deep history of our solar system and the enormous influence Jupiter has exerted over it the Italian astronomer JPI Piatti discovered series on the 1st of January 1801 and
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at first he reported his findings as the discovery of a new comet in the region of space between Mars and Jupiter but it seems from the start that all of his instincts told him this was something else in announcing his observations in a letter to two fellow astronomers he noted that since its movement is so slow and rather uniform it has has occurred to me several times that it might be something better than a comet piai and his colleagues speculated that rather than
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a comet they might have found something even more spectacular a new planet but after just 41 days of observation Patti fell ill the path of the newly discovered object strayed into the direct glare of the Sun and in a Twist of high astronomical drama the newly found Planet series was lost with just a tiny number of observations across a small piece of Sky calculating series's orbit was deemed
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impossible using the mathematics of the time and many contemporary great mathematical Minds predicted it might never be found again it would take the work of a young German mathematician Friedrich gaus to solve the problem attracted to the difficulty and elegance of using mathematics to compute the orbit from just a few coordinates gaus pioneered a novel mathematical method that allowed him to calculate the path of series using just three of Pat's original observations on the
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very last day of 1801 two astronomers using gauss's methods searched the region of the sky to which the calculations guided them and to everyone's delight and relief recovered series from the darkness gaus became a mathematical Superstar and siries firmly back in our sights was stamped with the classification of a planet for the next 50 years siries and its companions Vesta Palace and Juno remained listed as planets until as we have seen the discovery of a raft of
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other objects in this region of space gave rise to our identification of the asteroid belt and for series it was downhill from there on until in 2006 it was classified as a dwarf planet for the next 160 years little was known about this tiny Planet orbiting the Sun at a distance of 413 million kilm we knew that it was the biggest object in the asteroid belt and the only object amongst the millions of asteroids that was large enough to have been rounded by its own
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gravity we could also make a good approximation of its size at around 1,000 km in diameter and composition Rock and Ice what else but when it came to surface features even the powerful eye of the Hubble Space Telescope could make out only the vaguest of features intriguingly strewn across its surface it would take Dawn's arrival for us to truly understand the complexity of this world and its history even in the early approach phase of the mission daor was able to
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capture a quality of imagery that at once gave a new perspective on the long hidden surface it was no surprise to find it heavily cratered but while speeding towards series Dawn beamed back a series of mysterious images revealing a number of bright spots on the surface of what we had thought thought would be a dull dead and Frozen world not what you would expect on a planet that was assumed to be entirely geologically inactive the brightest of all of these highly reflective
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areas was imaged near a massive crater known as aat at 92 km wide and 2 km deep it's one of the biggest on the surface of series spot five as it became known is in the center of the crater and became the focus of intense investigation as Dawn G its's 3 and 1/2 year residency in orbit around series the crater is thought to have formed from a large scale impact around 80 million years ago and so the presence of what appeared to be geological active material on the surface
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was particularly surprising and at first left the mission scientists perplexed not only that but a haze was also seen to periodically appear above spot five suggesting something was going on beneath the surface after detailed analysis using Dawn's full range of Imaging and spectroscopic capabilities we now believe that spot five is the result of a geological Hot Spot the brightness created by the highest concentration of carbonate minerals ever found outside the Earth in a dome
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structure right in the center of the crater why does this matter well we know that this type of salt can only be formed in the presence of liquid water and it's almost certain that an impacting asteroid could not have delivered such material to the surface of Series so the upwelling in which it's found suggests that it comes from deep within this world it now seems that spot five is
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the remains of an ice volcano one that is perhaps still partially active and thus able to create the haze we have observed the two brightly colored patches inside it are thought to be the salty residue left by this ancient formation deposits of sodium carbonate from an erupting ice volcano that may have first been triggered by the impact that created the crater however the Dome likee shape
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upon which the deposits sit is almost certainly evidence of geological activity below the surface suggesting that hydrothermal activity was involved in bringing the salts to the surface and spot five is far from isolated we've now seen areas like the ones in AA all over the Sur surf of series and this begins to paint a tantalizing picture of series's past a past where heat from within
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the planet created a subsurface Ocean or at least localized pockets of water that surged upwards in the form of great ice volcanoes bringing with them on the asteroid the carbonate salts that we see sparkling today as Dawn delved deeper beneath the surface the surprises kept coming thick and fast Dawn was able to accurately measure the overall R density of series and found it to be 2.16 G per cubic cm Which is less than you'd expect for a rocky body series is about 2/3 the
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density of our moon which suggests that as well as rock the asteroid must also hold significant amounts of water ice this had been suspected long before Dawn arrived but with our eyes and ears now at work as Dawn Circle Series it was able to take precise measurements and so uncover anom IES in its orbit that revealed something remarkable about this lump of rock and Ice by carefully mapping the
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shape and gravitational field we found that the Rock and Ice weren't evenly distributed it appears that Siri's interior is nothing like that of other asteroids in the belt instead it appears to have a rocky core surrounded by an icer crust this is not the jumbled structure of an asteroid the differentiation into layers that was discovered by Dawn is something we only see in planets it seems
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that around 4.5 billion years ago series had taken its first steps to becoming a fully fledged world and then something went catastrophically wrong so we now think that 4.57 billion years ago a young rocky planet began to form in the region we call the asteroid belt in its infancy this protoplanet was a water world warmed from within by the heat left over from the violence of its birth even in
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this Frozen region of space orbiting 413 million kilometers away from the weak young Sun a deep saltwater ocean encircled the young series protected from the freezing temperatures of space beneath a thin layer of ice across this ancient embryonic World ice volcanoes broke through transforming and renewing the surface as it was bombarded by the bodies that swarmed around it today we see just the lifeless remains of this geologically active world in the distinct
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mountainous landscape and sparkling salts that clothe it but the subsurface ocean is long gone locked away as a thick layer of ice between the Surface and the core this is a nent planet that has been in deep stasis for billions of years Frozen in time it is a precious piece of History an artifact that allows us to Glimpse our Origins and understand just how precarious a time this was for every planet including our own we now think that before siries could fulfill her potential
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a great disturbance sent shock waves through what would eventually become the asteroid belt and cut its young life short the vast amounts of rock and Ice that made this part of the young solar system such a rich breeding ground for the birth of planets was wiped clean of almost all of its Building Material leaving just a fraction of the material needed to build a planet and nothing from which series could grow computer simulations suggest that originally the asteroid
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belt contained enough material to build a planet the size of Earth and perhaps that was once sir's Destiny perhaps it was even destined to become a Subterranean Water World capable of supporting and nurturing life but before any carbon chemistry could spark into Seeds of Life series's fate was sealed Tri Ed by the wanderings of a giant that lay Beyond in the darkness we now suspect that
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at this early time in the life of the solar system as Jupiter circled the young Sun something caused the giant planet to change course and spiral inwards towards the sun plowing right through the asteroid belt the resulting gravitational chaos scattered the contents of the asteroid belt far and wide embryonic planets were knocked out from their orbits the building material of these planetesimals was thrown out and in towards the sun Jupiter's charge displaced 99.9% of the
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material in this region of space leaving series half formed half built but with nothing more from which to grow in this part of the solar system at least the planetary construction business was shut down for [Music] good how do we know such a dramatic turn in the Solar systems history took place the greatest evidence has come not from our own system but from the study of other star systems and their planets a field of science that has exploded in the last 30 years until the 20th
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century the only evidence of how planetary systems formed and functioned came from one single Source Earth's solar system our own backyard was the one place that we had the technology to study and that meant our view of how a planetary structure worked was deeply skewed toward the seemingly simple structure of a star at the center four small rocky planets orbiting it then a ring of millions of
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Rocky pieces remnants from its formation followed by a series of four more planets the gas giants it has a pleasing regular structure about it all the rocky planets sitting close to the star and the gas giants orbiting further out we suppose this must be the natural order of things the way that solar systems have to form but that all changed when the technology arrived to allow us to detect planets around distant Stars it soon became clear that our solar system is not typical
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at all it may in fact be very odd [Music] indeed in most of the planetary systems we've observed the setup is remarkably different to our own as we have extended our gaze and explored the structure around other stars with the help of exoplanet hunting technology like the extraordinary Kepler Telescope we've begun to see that one of the most common Place categories of planet is completely
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missing from our own inward of mercury our solar system is essentially an empty void but look at the equivalent region around most stars we have studied and we often find it packed with a completely different class of Planet super Earths these worlds are between 2 and 8 times the mass of the Earth with thick hydrogen Rich atmospheres they sit incredibly close in to their Stars orbiting at a rate that makes the head spin the first discovery of a super Earth around
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a main sequence star like our own was made back in 2005 by a team led by Eugenio Riviera using data from the kek observatory in Hawaii glea 876 D is an exoplanet almost s times the size of the Earth which is orbiting just 3 million kilm away from its red dwarf star glea 876 thought to be a rocky planet with surface temperatures estimated to approach 341° C with an orbital period year of just under 2 days this is a world completely inhospitable to life to understand why this rocky
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planet is found so close into the sun we need to understand the rest of the planetary system and in the case of glea 876 that means looking at the three other planets circling further out from the Star the first of these planets to be discovered and one of the earliest ever observations of an exoplanet is 876 B discovered in 1998 by the legendary Planet Hunter Jeff Marcy we believe this world is a gas giant at least twice the size of Jupiter but orbiting much closer to its parent
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star in fact at just 0.2 Au 30 million kilm this massive planet is orbiting much closer in than Mercury orbits the Sun at that distance 876 B zooms around on its orbit once every 61 days compared with Jupiter's stately 12year Journey around the Sun either side of this giant planet are two other worlds 876 c a gas giant 3/4 the size of Jupiter and 876 e a planet we think is about the same size as Uranus all four of these worlds orbit within a distance less than the
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orbit of mercury it's as if the whole planetary system has been squashed packed in tightly around the star and this configuration is far from rare as we've explored more and more planetary systems we've discovered this combination of super Earths and close orbiting gas giants is the nearest to a normal layout we observe what underlies this is the fact that planetary systems are not the static and stable systems we had always assumed them to be far from the heavens being full of
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planets following Eternal Clockwork rhythms most systems including our own are chaotic Dynamic and turbulent the reason for this is that particularly early on in the infancy of a new system planets frequently migrate forming in one part of the system before wandering off into different zones there are a number of different mechanisms Behind These wanderings but perhaps the most formative on
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the evolution of a planetary system is the type 2 migration that occurs to gas giants early on in their life lives a gas giant planet like glea 876 C would almost certainly have begun its life far further out than it is today in a region more akin to where we see Jupiter or Saturn in our own solar system at the very earliest stages of its existence as this newly formed Planet orbited within the cloud of gas and dust of its formation the planet began to clear a path in its wake
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and in doing so triggered a process that would transform its orbit a shift in its gravitational interactions with the gasr disc would have slightly reduced its angular momentum and sent the planet on a different course spiraling inwards towards the star at the center of the system this seems to be a common path trotten by many gas giants around distant stars and is the reason we find a preponderance of so-called hot Jupiters massive gas giants sitting so close to
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a star that they orbit it in less than 10 days the effects of these migrations have an impact far greater than just this though in plowing inwards a migrating gas giant like glea 876 c ends up clearing vast areas of space halting any planetary formation and instead pushing material inwards towards the star creating the perfect scenario for super Earths like 876 D to form this Cosmic pinball is the reason why so many of the planet systems we've been able to explore follow
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the pattern of hot is Jupiter and super Earths but why not ours what was different about the history of our solar system that led to the more expansive layout we see today scientists suspect the answer lies with our own gas giant Jupiter and the journey it took across the young solar system the story of Jupiter begins not in the far reach of the solar system 778 million km from the Sun where it orbits today but much closer in we now think that almost 5 billion years ago Jupiter
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formed around 520 billion km 3.5 AU from the Sun at this time the young giant was still surrounded by the disc of gas and dust from which it had Arisen but Jupiter began to slowly but surely clear its path through the cloud and debris over a relatively short period of time of just a few million years the path through its orbit became completely clear and just like the huge gas giants we've observed around alien stars like Lisa 876 this caused Jupiter to start spiraling inwards
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towards the sun this process was driven by the gravitational interaction between Jupiter and the cloud of gas which as it fell into the sun itself effectively dragged the planet with it this was no subtle shift in Jupiter's orbit while it spiraled inwards it would keep falling closer and closer to the Sun passing through the region of asteroid belt and robbing planetary hopefuls like siries
1:02:04
and Vesta of the material they needed to complete the journey to planethood but this was just the start of Jupiter's reign of terror further and further the young Jupiter fell until it reached the vicinity of where Mars orbits today just 225 million kilm or so from the Sun this was no quiet visitor to our local neighborhood a planet of this size can wreak havoc just by its proximity and
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Jupiter's arrival in the inner solar system did just that transforming the destiny of many of the emerging new worlds including our own Lee Fletcher from Jupiter icy Moon Explorer Mission explains this action as a tug of war between the orbits of Mars and Jupiter we have a large accumulation of objects Rocky objects mostly known as the asteroid belt they're not able to form an agglomerate into
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a a complete Planet because of the constant tug of war between the gravitational forces of the Sun and of Jupiter so what we see today is a large disc of objects that could be the remnants left over from the formation of our solar system to understand just how powerful a presence Jupiter must have been as it marauded around the inner solar system we need to look no further than the worlds it has in its eyon grip today Jupiter has at the time of writing 79 known moons held in its
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orbit by the powerful gravitational field that is generated by the planet's enormous Mass a powerful force field that reaches out from the planet deep into the solar system it's what has made Jupiter so destructive in the past and through our exploration of the Jovian system we have also witnessed its awesome power today nowhere is this power more dramatically revealed than on iO the closest of all the moons to Jupiter IO orbits just 350,000 km from the cloud tops of its mother
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Planet a distance that makes it a gravitationally tortured World a volcanic vision of hell this is the most geologically active object in the solar system with over 400 active volcanoes from which lava flows stretch hundreds of kilometers across the moon's surface and vast clouds of pyroclastic material blow hundreds of kilometers up into space creating distinctive umbrella-shaped plumes above
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its surface Sur the surface of IO is perhaps the closest that our solar system has to offer of a vision of hell and all of this activity is created not by ancient internal heat as we see on our planet Earth but by the power and the influence of Jupiter's gravitational pull here on Earth the volcanism that we see across our planet is driven by a combination of the heat that remains from our planet's violent formation and that which is released from the decay of radioactive
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elements locked away in the planet's interior this heat combined with the high pressures below the surface creates the molten rock that pools within the mantle layer of the Earth and then in certain places this magma finds a root to the surface creating a volcano on iO the volcanism is nothing like this instead it's being generated by a completely different mechanism a process called
1:05:18
tidal heating that is driven in large part by its proximity to Jupiter and the gravitational tug of war between other nearby moons IO is caught between the vast mass of Jupiter on one side and the three other gilean moons Europa gmed and Kalisto on the other a dynamic that pulls in different directions to Violent effect it's a dynamic that we see in part on our planet every day as the force of gravity flexes its muscles in the interaction between the Earth and the moon
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creating the twice daily EB and flow of our tides on Earth the gra gravitational tug of the Moon creates a tidal force that moves vast volumes of water around the planet with the biggest difference between low and high tide creating a shift of a maximum of 12 m in the height of water the same principle also applies on the surface of the Moon where the gravitational pull of the earth creates Tides not of water but of rock Moon tides are small changes in the height of
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rocks on the lunar surface caused by the pull of the Earth's gravity in the case of the Earth Moon system these Rock tides are measured in just a few centimet but IO tells a very different story IO is roughly the same distance from Jupiter as our moon is from Earth and both moons are of equal size but because Jupiter is so much more massive the tidal forces it generates are much greater with the
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gravitational pull of Jupiter moving the Bulge of Rock tides up to 100 m between low and high tide that's five times the height of any tide here on Earth lifting the levels of solid rock up and down in fact IO contains the least amount of water of any known object in the solar system but this is not the end of io's torture its relationship with the other large moons particularly the next moon out Europa also adds to the destructive forces that are pulling the very substance of IO
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apart IO whips around Jupiter much quicker than our moon goes around the earth once again due to the mass of Jupiter completing an orbit once every 42 hours if left alone IO would complete this orbit in a near perfect circle around the giant planet but IO is far from alone and with Europa circling Jupiter precisely once every two orbits of IO it means that in every second orbit Europa and IO line up and that rhythmic orbit has consequences this is what's known as
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an orbital resonance and the result is that it gives IO an additional gravitational kick that moves the moon's orbit out of a circle and into an ellipse ganam is also in a resonant orbit with IO in a 1:4 orbital period ratio and the outcome of this is that as IO orbits the gravitational forces are constantly shifting and changing and that stretches and squashes the moon creating vast amounts of friction that causes its interior to heat up it's a process called idal Heating and
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it's this generation of heat that produces io's volcanoes raising the temperature in its interior to over 1,200 de C and creating the violent world of Lava Lakes and Volcanic plumes that we've witnessed Through The Eyes of Galileo and Voyager the pull of the two moons on iO also stops IT gradually falling inwards to Jupiter and being completely ripped apart IO is an extraordinary example of the power power of Jupiter and a demonstration of how this planet can shape
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and change the destiny of Worlds because of its huge mass and the intense gravitational force this produces any planet or Moon that gets too close to it is under threat while Earth is at a relatively safe distance today 4.5 billion years ago as Jupiter moved into the inner solar system it began to exert its power right in the spot where Mars and our own world were beginning to form
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4 and a half billion years ago the region of the solar system we call home was densely packed with gas and rock a planetary Nursery full of embryonic worlds each with a different Destiny in store but this fertile space was about to be thrown into chaos by the Solar System's most unwelcome of visitors as Jupiter was pulled from its distant orbit and continued its inwards descent it paused in this planetary breeding ground the consequences of this action would be
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significant and far-reaching detailed simulations of the impact this wandering Jupiter would have made suggest that the fate of any super Earths caught in mid formation would have been thrown into chaos the models suggest that Jupiter's inward Journey would have driven thousands upon thousands of planetesimals many over 100 kmers wide spiraling into the inner solar system this planetary breeding ground was turned into to a Battleground as Jupiter's presence through the
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orbits of any newly forming super Earths into the overlapping Paths of thousands of massive blocks of rock and Ice the result was Carnage a Cascade of collisions that blew apart planets and left a trail of fragmentary worlds in its wake a chain reaction that would culminate in the formation of a spiraling swirl of gas dust and rock that would have swept any surviving super Earths towards the
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Sun and ultimately to their destruction in what was just a fleeting moment in the history of our solar system its Destiny changed forever our planet would not fit the norm of super Earths and the tightly packed gas giants that we see across the Milky Way instead we think the inner solar system would have been swept clear of up to 90% of the rocky material thrown in by Jupiter with just crumbs remaining four small terrestrial planets began to form from the rubble with Jupiter
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marauding in its orbit much of the material that could have gone on to form Mars was lost leaving the planet with enough scraps to make a planet half its potential size and transforming it from a possible Habitat For Life to a world that would freeze and die in its adolescence just that little bit further in Earth found itself forming in a slightly more substantial ring of gas and dust that would make it the largest of all the terrestrial planets a lucky Escape for
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our future home because had Jupiter continued on its inward path Earth might never have formed at all but just as it looked like it would sweep everything away Jupiter stopped in its tracks on its inward Journey Jupiter had transformed the inner solar system sweeping away the formative giant planets and leaving just enough material for Mars Earth Venus and Mercury to form but the stage
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was now set for another player to enter the story and shift the destiny of both our world and the solar system once again waiting in the shadows of the outer solar system another massive planet was lurking that we now think pulled Jupiter back from the brink Saturn a gas giant not as big as Jupiter but enormous nonetheless began its own slow drift inwards towards the sun formed much further out
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than Jupiter as Saturn began turning inwards it would have a profound effect on Jupiter's trajectory as the two giants Drew closer together they became locked in an intimate gravitational dance an orbital resonance that meant that for every orbit Saturn made around the Sun Jupiter made two circuits exerting a regular periodic gravitational influence on each other as the two giant worlds passed close by the result of of this orbital resonance between Jupiter and Saturn
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cleared out all of the gas and dust between the two planets creating a gap in the dis of the early solar system and this interaction between the two resonant planets and the gas and dust at the edge of the Gap resulted in both planets changing Tac the orbits of both Saturn and Jupiter began to move outwards away from the Sun preventing Jupiter from moving any further into the inner solar system earth was given a reprieve and Jupiter was dragged back out into the asteroid belt once
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more this change in Direction has become known as the grand Tac hypothesis a nod to the action of a sailboat as it tacks and changes course while it travels against the direction of the wind just like a sailboat the theory suggests Jupiter tacked around 1.5 AU from the Sun in the current orbit of Mars changing direction and pulling back out to its current orbit at 5.2 Au it's a theory that's been driven by using Advanced Computer modeling which helps to explain many of the
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inconsistencies between our solar system and the hundreds of other planetary systems we've recently observed it's the grand Tac that accounts for the lack of super Earths and explains the presence of only a handful of small rocky worlds with thinner atmospheres than those observed around around other stars the grand Tac also allows us to explain the unusually small size of Mars which simulations predict should be at least half the mass of the Earth if not bigger rather than the
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0.107 Earth's mass we find it to be it also helps explain the odd inhabitants of the asteroid belt transformed by Jupiter's Journey not just once but twice across this region of space this is why we see half finished planets like cies and Vester left starved of building material and an asteroid belt that has a surprisingly small Mass with objects that appear to originate from both inside and outside Jupiter's orbit and have a wide range of eccentric orbits themselves
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Jupiter the father of the skies and ruler of the heavens had spread its hand far and wide sculpting the precious solar system we see today in the space of just a few million years before coming to rest though it would Grant one more precious gift to the newly forming planet Earth as Jupiter was dragged out crossing the asteroid belt for a second time it encountered a region full of objects rich in water and bearing minerals and Jupiter's trajectory caused these objects to
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be flung back into the inner solar system they crashed into the young planets and moons with an intensity never seen before or since in a period known as the late heavy bombardment it transformed the makeup of the inner solar system delivering a large percentage of the water Earth holds on its surface today it's extraordinary to think that it was Jupiter that was responsible for the delivery of the most important ingredient of Life the water that provided an ideal environment
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for life to spark and thrive in one unbroken line for the last 4 billion years this story offers an extraordinary understanding of the power Jupiter has wielded over all of our Lives the more we learn about the formation of solar systems and the more we try to model a system like ours with four terrestrial water-rich planets close to the star and the gas giants further out the more we learn that perhaps all these things had to happen these unlikely movements and interactions
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between the planets were necessary to produce a system like ours and a planet like ours so if events like the TAC of Jupiter are as we believe them to be extremely uncommon the conditions for the formation of earthlike planets terrestrial worlds with plenty of liquid water beneath the gentle pressures of a Thin Blue Line must be exceedingly uncommon it's a humbling thought to begin to comprehend that the Earth may not just be a rare Rock in our solar system but a
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rock that only exists because of the rare system of planets within which it evolved all the evidence is beginning to suggest that we may be living on a tiny Oasis within a vast desert devoid of life and stretching out across the Milky Way today Jupiter has settled into a regular orbit at the far side of the asteroid belt its days of marauding through the solar system at an end established in a stable orbit for almost 4 billion years it has looked down on our
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planet as a distant light in the sky unchanging while the work of evolution by natural selection has transformed the first Sparks of life on earth into the endless beautiful forms that we witness today but although distant and seemingly detached Jupiter's influence has been far from benign the history of life on Earth has been interrupted by numerous cataclysms impacts with asteroids that have fundamentally shifted life again and again and the hand behind these disruptions
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it's Jupiter that has continued to hold immense sway over our planet exerting its influence on the asteroid belt with just the smallest of nudges the difference between existence and Extinction at 1653 UTC on the 18th of October 1989 the space shuttle Atlantis took off from the Kennedy Space Center in Florida carrying the Galileo spacecraft carefully packed away in its hold released into Earth's orbit from the cargo bay just a few hours later the probe would
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begin a six-year journey to Jupiter that would utilize flybys of Earth and Venus to propel it on its 4.6 million km voyage across the solar system entering orbit around the giant planet on the 8th of December 1995 Galileo would not only become the first spacecraft to orbit Jupiter but also the first craft to orbit any of the outer planets it spent nearly 8 years in the Jovian system and explored the giant planet in its managerie of moons in intricate detail for the very first
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time revealing a host of new discoveries from precise measurements of Jupiter's atmosphere and observation of its giant thunderstorms to discovering liquid water under the surface of the Moon Europa and the first detailed studies of the intense volcanic activity of IO this was a mission that opened our eyes to the beauty and diversity of the Jovian system in a level of detail that we could scarcely have imagined possible but long before Galileo even arrived this two-ton Explorer
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would already have changed our view of the solar system entering the asteroid belt in August 1991 Galileo performed the first close-up flyby of an asteroid passing within 1500 km of 951 gaspa and returning the first detailed images of this Rocky Remnant back to Earth its next close encounter would come almost 2 years later when flying past 243 Ida the probe discovered that this asteroid
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had its own Moon dactil as it has become known was the first asteroid moon ever to be discovered and the images are beautiful a tiny 1.5 km wide object in a chaotic orbit around its parent rock after this unexpected encounter Galileo continued its long journey across millions of kilometers of empty space still four years away from its ultimate rendevu with Jupiter but by luck rather than judgment this tiny probe happened to be traveling towards Jupiter at the precise moment
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it would be able to witness one of the rarest of shows our solar system has to offer on the night of the 24th of March 1993 as Galileo sped across the solar system three astronomers working at the Palomar observatory in California were attempting to spot and track what are known as near Earth objects undetected meteors that might be of Potential Threat to our planet that evening David
1:22:04
Levy along with Carolyn and Eugene Shoemaker took a series of images using the 1.5t Schmid telescope lurking in one of them was an unusual artifact that grabbed the attention of the team streaking across the image was an object that although nowhere near the Earth was of immediate and immense interest a comet that appeared not only to be unusually close to Jupiter but also seemed to have multiple nuclei a fragmented series of rocks trailing across 1 million kilometers of space in
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a moment of wondrous astronomical Serendipity the team had discovered the first ever comet in orbit around another planet a comet that had not only been captured by Jupiter's immense gravity but had also been pulled apart by it Shoemaker Levy 9 as it became known because it was the ninth Comet this team had found was a comet unlike anything we'd seen before quickly confirmed by further studies to be orbiting Jupiter and thought to have been captured from its solar orbit back in
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the late 1960s or early 1970s astronomers were able to wind back through its orbital history and calculate the precise moment the comet was ripped apart passing just over 40,000 kilm above Jupiter's Cloud Tops on the 7th of July 1992 we think Shoemaker Levy 9 fell within the planet's Ro limit and this 5 km Comet was ripped apart by the huge tidal forces generated this close to the planet it disintegrated into 23 pieces visible to us here on Earth labeled fragments a to W with the
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biggest up to 2 km in diameter this alone was a remarkable Discovery A visual representation of Jupiter's colossal gravitational power but if that wasn't enough it quickly emerged from orbital calculations that the comet seemed to be on a trajectory that would ultimately take it straight through the center of the planet Shoemaker Levi 9 was on a collision course with Jupiter and as if we had scheduled it ourselves the date of the predicted impact was July 1994 perfect timing for
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the spacecraft we already had on route by the beginning of July 1994 Galileo was 238 million kilm from Jupiter on the very edge of the asteroid belt and speeding through space towards its final destination ahead of it KET schuma Lev 9 was entering its final few days in orbit around the planet with the first impact expected on the 16th of July the world's most powerful terrestrial telescopes were trained here as well as some of our space observatories from the newly
1:24:53
fixed Hubble Space Telescope scope to the ulyses spacecraft which turned its gaze from its primary job of watching the sun even the distant Voyager 2 probe 6.6 billion kilm away Beyond Neptune was able to look for radio wave emissions from the impact and employ its ultraviolet spectrometer to make distant observations but for all of this technology peering across the solar system there was only one set of eyes that would be able to see the actual first impact the comet would first
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first hit Jupiter on the side turned away from the earth but Galileo was approaching on the night side of the planet which would give us a unique view not visible from Earth of our first ever observation of a collision between two objects in the solar system the first impact occurred at 2013 UTC on the 16th of July when fragment a entered Jupiter's southern hemisphere traveling at 60 km a second hitting the planet with an estimated force of 300 million atomic
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bombs with its instruments trained on the impact Galileo recorded the subsequent Fireball which reached temperatures of over 24,000 de Kelvin creating huge plumes that stretched over 3,000 kilm high it was a breathtaking spectacle that quickly came into view from Earth as the rapid rotation of Jupiter brought the impact sights into Clear Sight revealing a huge dark spot on the surface over the next 6 days 21 distinct impacts were observed as each of the fragments impacted
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with its own distinct set of characteristics fragment G was the largest of all the impacts striking Jupiter on the 18th of July it created a vast scar on the surface of the planet stretching over 12,000 km across this extraordinary spectacle continued until the 22nd of July when fragment W brought the show to a close leaving just the scars of the impacts to slowly fade away way over the following months Galileo had given us a ringside seat for this rarest of phenomena aided
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by our technological eyes and ears on Earth and across the solar system we were able not only to witness a collision like this for the very first time but also to harvest a vast amount of data it transformed our understanding of the composition and Atmospheric dynamics of Jupiter allowed us to precisely measure the actual size and composition of the Comet itself but perhaps most important of
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all it enabled us to study a cosmic Collision firsthand revealing one of the most important dynamics of Jupiter and the power it exerts over every object and planet in the solar system including Earth before it fragmented Shaker Levi 9 was at least 2 km wide and weighed over 800 million tons traveling through the solar system in an orbit that would have taken it hurtling through the inner terrestrial planets and perhaps even close to Earth if such an object had hit us
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the consequences would have been devastating sending a vast amount of dust and debris into the air creating a global smog that would have darkened the planet and cooled the atmosphere leading to a catastrophic impact on all life on Earth we will never know whether Shoemaker Levy would have posed a real danger to our planet but we do know that Jupiter removed the threat and such acts of planetary protection are Are Not Unusual the impact of this Comet demonstrated
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in spectacular fashion the role of Jupiter as a cosmic vacuum cleaner using its vast gravitational power to capture objects like sl9 by bringing them into its orbit and incinerating them on impact we think Jupiter acts as the grand protector luring in objects that might otherwise pose a threat of collision with the Earth but as we have so often seen with the story of Jupiter no Act is ever
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truly benevolent for every potentially dangerous object it Shields us from it can throw another in our Direction that's because of the influence it exerts over all the objects in the asteroid belt it's easy and quite natural to think of the asteroid belt as a single homogeneous structure a ring of rocks orbiting in an orderly fashion around the Sun but it's nothing like that at all in reality each of the millions and millions of pieces of rock is following its own individual
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orbit distorted and eccentric orbits that create what appears to be a chaotic cavalcade around the Sun but although there are complex patterns there is also structure and nothing has more influence on that structure than Jupiter the silent conductor of the asteroid belt in some way every asteroid dances to Jupiter's tune whether it's the Trojan asteroids orbiting ahead of and behind Jupiter or the Hilda asteroids that orbit around in three groups due to the delicate
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interplay between the gravitational pull of the Sun and that of Jupiter every asteroid is in some way caught between the two largest objects in the solar system in such a chaotic complex system collisions between asteroids are inevitable and disturbances to an orbit are commonplace all it takes is for an asteroid to line up with Jupiter and the resultant gravitational kick it sees can send an asteroid hurtling outwards banishing it to the far edges of the solar system or inwards
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towards the inner planets it's by this mechanism that Jupiter continues to exert its influence across every corner of the solar system over the last 4 billion years from its distant orbit 778 million kilm away from the Sun Jupiter has repeatedly played with the destiny of our planet and the path of life upon it the surface of the Earth is strewn with the evidence of cataclysmic collisions that have significantly shaped the history of the planet from the delivery of huge
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volumes of water almost 4.5 billion years ago to the near Planet destroying events of the late heavy bombardment and even the formation of the Earth Moon system all of these momentous events can be linked to the shifting influence of Jupiter and its gravitational strangle hold on objects across the solar system over millions of years the evidence for many of these collisions has been lost or hidden under the everchanging surface of our planet but as we've been able to see it
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impact sites like the Barringer Crater Jupiter's hand is never far away from shaping events on the surface of Earth the discovery of one such impact crater underneath the yakatan peninsula in Mexico back in the late 1970s has revealed evidence of an event that in a single moment changed the course of life on Earth perhaps more profoundly than any other transforming the very possibility of
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our own existence around 66 million years ago in the far reaches of the asteroid belt an object at least 15 km wide was making its final orbit of the sun just one asteroid among Millions this insignificant object had been following the same path for Millions if not billions of years but then something changed exactly what caused it to alter its path will never be known but the most lik explanation is that a gravitational nudge from Jupiter pulled it out of its innocuous orbit and
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sent it on a very different trajectory a direction that would ultimately bring it on a collision course with Earth traveling through space it would have descended through our atmosphere in just a few seconds before striking the Earth with a force equivalent to 100 million megatons of TNT the impact generated a fireball so hot that anything within a 1,000 km radius was instantly vaporized leaving a crater 180 km wide and 20 km deep today the town of chick shaloo sits near to
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what we think is the center of the impact site and lends its name to the crater that stretches out west onto the yakatan peninsula and East into the Gulf of Mexico the evidence for this giant impact doesn't just sit in the partially hidden chick shal looop crater but also in a thin layer of sediment found throughout the world that contains unusually high levels of idium this metal is exceptionally rare in the Earth's crust but is found in abundance within asteroids
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so we believe its presence in the thin layer of sedimentary rocks around the globe dating back 66 million years ago is a direct remnant of the huge rock that struck the Earth this geological signature is known as the k PG boundary because it marks not just the impact itself but a boundary between two epochs of life on Earth the end of the Cretaceous Period and the beginning of the paleogene it was an event that lasted just a few seconds but in the aftermath of the impact
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millions of tons of sulfurous rock were thrown up into the atmosphere and during the nuclear winter that followed 75% of all species were wiped from the face of the Earth in including the largest creatures ever to walk the planet in a global Extinction event that affected every continent simultaneously the age of the lizards was brought to an end as almost every species of dinosaur and many other species as well vanished in the space according to Steve Dash professor of Earth and
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space exploration at Arizona State University it was an event we would not like to see the likes of again if something size of the chick shalu imp packed to the killed the dinosaurs were to happen today it would just be utterly catastrophic for mankind the most immediate thing is you would have a magnitude 13 earthquake and then you would have tidal waves that could happen anywhere near water
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that are Miles High propagating out for thousands of miles in every direction and that's just for starters eventually so much dust would be kicked up into the atmosphere it would block sunlight destroy agriculture our infrastructure would fail today just traces of the dinosaurs remain these creatures that Ruled the Earth are now nothing more than a Dusty history captured in the fossil record one event one asteroid one orbit that was changed by the might of Jupiter without the
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distant planet's intervention it's possible that those giant lizards might still be here today and The evolutionary Niche that opened up for us with their removal might never have appeared there are many chance events not only throughout the history of Earth but also spanning the entire history of the universe for 13.8 billion years without which we wouldn't exist there's an unbroken chain of
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Life stretching back 4 billion years here on this planet but having said that there are major events that affected life and one of them without doubt is the asteroid that wiped out the dinosaurs and so in that sense it is true to say that without Jupiter we wouldn't be here the Godfather of the planets paved the way for humankind to inherit the earth and it has looked down on us benevolently
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ever since using its immense power to keep us safe a sleeping giant with its power undiminished an asteroid impact like the one that cleared the way for us to evolve 65 million years ago would have catastrophic consequences for our civilization were something similar to strike today to the naked Jupiter is one of the brightest points of light in the night sky and through a small telescope it is a beautiful banded World it feels distant Eternal disconnected from events
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here on Earth but the more we've learned about the history of the solar system the more we've come to understand that that is not the case Jupiter has played an important and perhaps decisive role in the stories of all the planets including Earth you see the solar system is just that it's a system complex interconnected and interdependent so the next time you see Jupiter just hold your gaze and think for a while about the fact that it is so much more than a point of light or a
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planet even Jupiter is the great sculptor of the solar system the destroyer and creator of worlds Saturn is a gas giant alive with storms of unimaginable ferocity a world of alien weather where diamonds rain down from the sky and bubbling vortexes whip around the planet so fast they catch up with their own tails and glistening in the distant light of the sun is a 500,000 mile ring of almost pure frozen water broken into millions of individual pieces this structure is unique in
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our solar system sculpted by the delicate hand of gravity yet for all of their iconic Beauty the Rings are just a fleeting Shadow an echo of Saturn's past and an ephemeral structure that has adorned the planet for a brief moment in its history and will soon disappear again Saturn is a place of many worlds encircled by at least 62 moons this managerie of satellites boasts worlds of astonishing variety Titan bigger than the planet Mercury is the only moon in
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the solar system to have its own substantial atmosphere while mimus is the smallest body in the solar system perhaps most astonishing of all though is Enceladus an ice moon with an ocean of liquid water inside that seems to contain all the building blocks of life composed of 96% hydrogen and 3% helium Saturn has a diameter at its equator almost 10 times the size of the Earth at 12,536 km its volume would hold 800 Earths however with a mass made up predominantly of gas the planet's
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density is remarkably low as the only planet in the solar system less dense than water if you could find a bathtub big enough to hold it Saturn would literally float in it beneath the frosty minus 178° C cloud tops the pressure rapidly increases under the huge weight of Saturn's dense atmosphere the hydrogen gas of the upper layers turns at first into liquid and then hundreds of kilometers further below the planet's Cloud tops into slushy metallic oceans of hydrogen we can
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only make an educated guess about the structures that lie within Saturn's unreachable core with temperatures at its Center exceeding 11,000 de C Saturn generates far more heat from within itself than it receives from a sun that sits on average 1.4 billion kilm away meaning that it must be generating its own heat with such extreme temperatures and pressures the structural makeup of this planet is uncertain and hotly debated according to planetary scientist and physicist
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Jonathan lenine if you go down down down through the hydrogen through the helium rain to this core of Rocky and icy materal material it's not rock and Ice it's some sort of atomic crystal where the elements of rocks and Ice the Silicon the oxygen the Magnesium are all together in a structure that doesn't exist in the rocks on the earth now in the case of Jupiter it might actually be warm
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enough that the core is a liquid that it's molten in the case of Saturn it's probably a solid core but definitely an exotic one undoubtedly there is a dense core at the heart of Saturn one that is almost certainly composed of iron nickel alloy and Rocky silicon-based compounds but exactly how this material behaves at such extremes remains a mystery from its surface all the way down to its
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Center Saturn is a world of mystery this gas giant along with its sister planet Jupiter is Worlds Apart in character from Mercury Venus Earth and Mars the terrestrial planets of the inner solar system it's hard to imagine how they could all have been created from the same ingredients the singular cloud of gas and dust that gave birth to every planet in our solar system but if we go back
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far enough in time we begin to uncover a history with a surprisingly familiar origin the beginning of Saturn's story is far more recognizable than its present day character would suggest because at the heart of all the ringed planets beauty lies a lost world a primordial one that disappeared from view billions of years ago and yet was the seed for everything that Saturn was to become without this early World there would have been no gas giant no rings of ice and no hope of an
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orbiting Oasis Of Life In the far distant reaches of our solar system the story of Saturn like that of all the planets began around 4.5 billion years ago in the light of the Awakening Sun a vast cloud of gas and dust swirled around our newly formed star and that prot interplanetary disc of gas and dust clumped and coalesced until it slowly began to form into a collection of embryonic worlds
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that would go on to become the four rocky planets sitting closest to the Sun millions of kilometers further out in the cold distant reaches of the solar system a similar story was playing out but this tale of planetary formation would follow a very different path that's because Saturn was molded Beyond a boundary called The Ice Line sometimes also called the snow line which is a frontier that marks the Divide between the terrestrial planets and the gas giants
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respective proximity to this line would lead the evolution of Saturn and that of its neighboring planet Jupiter to play out very differently the Ice Line as you might expect from the name is a way of dividing a solar system into two broad zones based on temperature inside the Ice Line the strength of a star is strong enough to keep keep things pretty warm but step onto the other side of the line and you've crossed a boundary where it becomes cold enough for volatile compounds
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like water methane ammonia and carbon dioxide to condense and freeze solid each of these compounds does of course have its own precise Ice Line due to the different specific freezing points of each individual compound but beyond a certain point the boundary begins to incorporate the freezing points of a large number of compounds today the IC line is thought to be around 5 Au that's around 750
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million km from the sun which means it lies well beyond the asteroid belt at a distance just before the orbit of Jupiter but in the infant days of the solar system that distance would have been much less with a weak young Sun shrouded in an opaque cloud of dust and gas the early Ice Line would have fallen about 2.7 AU from the Sun smack Bang in the middle of where we find the asteroid belt today we know this because we've been able to explore the makeup of the asteroids on either
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side of this line beyond the 2.7 Au line we've discovered the asteroids to be icy objects with large amounts of water ice locked away within them while on the inside of this line we find a very different class of asteroid dry and largely devoid of water it seems these bodies formed in a region of space that was simply too warm to allow substantial amounts of ice to exist why does the Ice Line matter in the story of Saturn's evolution in the early solar system as the protoplanetary
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disc swirled around the young Sun the Ice Line not only defined an important boundary in terms of temperature but it also created a dramatic difference in the abundance of material available to build a planet on either side of the line Beyond The Ice Line the lower temperatures meant that all of those frozen volatile compounds were swirling around in the cloud of gas as solid grains building blocks that provided vast amounts of additional material to feed into the process
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of planetary accretion and the impact of this simple physical difference was profound on our side of the line we find only rocky planets like Earth Venus and Mars while on the other side of the line there is not a single planet that we recognize as terrestrial just the gas giants of Saturn and Jupiter and the ice Giants of Uranus and Neptune Beyond to understand the reason for this Stark delineation we need to look back to a critical time in Saturn's history to the moment
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where the paths of the planets either side of this ice line began to diverge Saturn began its life not as a beautiful Jewel but as a tiny ugly ragged world just like its terrestrial cousins the origins of this gas giant planet began with the clumping together of tiny specs of G gas and dust that slowly grew into bigger and bigger clusters as this embryonic New World tumbled wildly through space days would have lasted minutes as the distant Sun lit its Twisted surface rising and
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falling in chaotic Rhythm repeatedly eventually as it grew this ragged Rock began to transform itself taking the new shape of a spherical world as it went from planetesimal to protoplanet on the warm side of the iceline the growth of the terrestrial planets came to an abrupt halt as these planets had secured stable orbits and began clearing their way through the protoplanetary disc the supply of
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raw ingredients ran dry and so their growth simply stopped starting with the runt of the litter Mars followed by Venus and then our planet Earth the largest of the rocky planets but on the other side of the Ice Line it was a very different story with no shortage of building material the growth of the protoplanetary Saturn was was able to progress at a rapid rate with abundant amounts of rock
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and Ice the young Saturn continued to grow quickly dwarfing any of the terrestrial planets that were forming in the far distant glow of the warming sun over a relatively short period of hundreds of thousands of years this plentiful supply of material smashed and clumped and grew until through a series of planetary scale collisions Saturn became the largest object for millions of miles in any direction the bigger it got the stronger its gravitational field grew and so it
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could attract ever more material into its grasp eventually the violence of its early life allowed Saturn to grow into one of the biggest worlds of rock and Ice the solar system had ever seen what did this world look like we simply do not know the detail of how any of the planets formed in the solar system is only sparingly understood these are events that happened 4.5 billion years ago and it's very much still cutting edge scientific research trying to piece together the barest
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of timelines let alone the intricate details of these distant events much of what we do understand of the evolution of our own solar system and the planets within it has been supported by our recent ability to study worlds outside it in neighboring systems the study of exoplanets has allowed us for the first time to peer into the evolution of other star systems and witness the formation of hundreds of different planets rather than the eight in our own backyard much of this
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evidence supports the idea that Saturn was once a world of rock and a world that grew to perhaps 10 or even 20 times the mass of the Earth as it gorged itself on the available matter this was a world we would at least have vaguely recognized a place it is almost possible to imagine a world that you could stand on and Survey but it was a world that wouldn't last the fact that Saturn grew to such a size had significance Beyond just scale its size pushed the planet towards a very
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different Evolution changing its relationship with the environment and ultimately sending it on a completely new path it's because of its immense mass and its place in the solar system that Saturn wouldn't remain a rocky world for long the history of the exploration of Saturn is littered with many of the greatest names in the field of science Galileo galile was the first to peer at her through a telescope in 1610 mistaking the faint outline of the Rings for Two Moons on
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either side of the planet he famously reported the planet appeared to have ears 2 years later however when he looked up again the peculiar structures on either side of the planet had disappeared we now know this is because the Rings were facing the Earth Edge on at the time of observation but for Galileo this was a strange and mysterious anomaly it would would take almost 50 years and the more
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powerful telescope technology of Christian haens to solve the problem using a 50mm refracting telescope haggens was the first to spot a moon of Saturn publishing his discovery of Titan in 1656 at the same time his observations led him to begin formulating a theory to explain the strange ears that Galileo had first seen not moons but a ring around the planet uncertain that he had enough
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proof to convince the scientific community of his hypothesis Hagens did what was common at the time he published his thinking not as a preliminary hypothesis or even as a line of Investigation but instead in order to Mark the territory and protect his reputation he announced his Discovery in the form of an anagram a AAAA AA c c c c c d e e e e e g h i i i i i i i i l l l l m m nnnnn NN n n o o o
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o p p q r r s t t t t t u u u youu for 2 years the anagram remained unbroken protecting hen's claim to be the first to identify the Rings while also giving him enough time to build the evidence to make the hypothesis defendable it wasn't wasn't until 1658 that haens revealed the meaning of the anagram to be a Latin sentence anelo kingor tenui Plano nosam coherente at ecliptic inclin which
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means it is surrounded by a ring thin and flat never touching oblique in relation to the ecliptic with the rearrangement of 62 letters one of the most beautiful structures in the solar system the rings of Saturn had been revealed to the world if not yet understood while Giovani Cassini and William herel went on to discover more moons of Saturn and to detail structures within the Rings including the 4,800 km gap between the A and B ring that would later become known as the Cassini
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division we still imagined the Rings as one great disc a flat solid circle of material encircling the planet within it was p Simon llas the French Newton who was the first to suggest in 1787 that such a singular structure around a planet would be unstable and instead was more likely to be comprised of a number of solid ringlets by the mid 19th century it was the turn of the great mind of James Clark Maxwell to investigate the Rings unpicking centuries of conjecture around the
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nature of the Rings he demonstrated for the first time through a series of mathematical proofs that any solid structure be it single ring or ringlets would be unstable and so unable to exist around the distant planet therefore Maxwell concluded the Rings must be composed of a huge number of small particles all orbiting the planet independently in his words every particle of the ring is now to
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be regarded as a satellite of Saturn disturbed by the attraction of a ring of satellites at the same mean distance from the planet Each of which however is subject to slight displacements the mutual action of the parts of the Ring will be so small compared with the attraction of the planet that no part of the Ring can ever cease to move around Saturn as a satellite with Maxwell's publication on the stability of the motion of Saturn's rings in 1859 our modern understanding of
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this distinctive feature of Saturn had begun but it would be another 120 years before we'd get the chance to EXP explore the most remarkable bodies in the heavens as Maxwell described them up close at 1426 universal time on the 1st of September 1979 after a 6-year journey from Cape Canaveral across over a billion kilometers of space the Pioneer 11 spacecraft took us within touching distance of the Rings of Saturn for the very first time as our first explorer to cross the boundary
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of the Rings pioneer a flew across the ring plane beyond the outer ring enabling it to photograph the saturnian system in extraordinary detail sending back a series of images that revealed the ringed planet in Greater resolution than we could ever have seen from Earthbound observations on its way through the ring plane Pioneer was able to take the first close-up measurements of the Rings and in doing so discovered not only a new ring system the F ring but also two new moons
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of Saturn in fact the spacecraft flew so close to the as then unknown Moon passing at a distance of just 6,676 km it was lucky the mission didn't abruptly end with a massive Collision we now know Pioneer had encountered either Epimetheus or Janus but we're still not sure which one of these two similar sized moons it was as both sit in the same orbit around Saturn traveling at a speed of 11 14,100 kmph Pioneer passed within 21,000 km of Saturn's Cloud tops making its
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closest encounter at 1629 us On That September day before speeding off beyond the Rings and onwards on its Journey to the outer solar system as well as taking 440 images of the saturnian system Pioneer measured the characteristics of Saturn directly an array of sensors were able to confirm that this giant planet was a bitterly cold world with an average overall temperature of minus 180° c and a composition made up almost entirely of liquid hydrogen but beyond the basic
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data perhaps Pioneer's greatest achievement was to plot a course through the Satan system and make its way safely through the ring system while returning data back to Earth now the stage was set for the two Voyager probes already well on their way across space speeding towards the ringed planet equipped with an even more advanced array of Technology ready to probe even deeper into Saturn's Mysteries the Rings were named essentially in order of Discovery in terms of
1:57:35
the main Rings it starts at the outermost which is the A- ring and then goes into B ring where most of the mass is and there's a faint c-ring and an even fainter d-ring inside that then the earring was discovered around 1980 when the Rings as viewed from the earth were Edge on that's the one that's clearly associated with Enceladus then Pioneer 11 discovered the fing and then Voyager discovered the G ring and the g ring we know is associated with a moon called Eon
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which is the source material for the ring at that stage we stopped using the letters as a nomenclature so there are other individual rings that have been named but they tend to be Rings or ringlets that are in the main ring system itself car Murray Cassini mission on the organization of Saturn's rings just over a year after Pioneer had exited the saturnian system early in November 1980
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Voyager 1 swept in with its highdef cameras primed and ready for action As It sped past Saturn at 17 km/s it was able to produce a wealth of new data about the planet rings and moons one of its key discoveries was the identification of three new moons Prometheus Pandora and Atlas the mission revealed detailed relationships between these moons and the ring system within which they sat
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which also confirmed a long-standing theory about the structure of the Rings at least the first two of these moons are shepherding moons satellites that exist within the narrowest rings of Saturn and play an essential role in keeping the delicate structures in place by their gravitational interactions with the billions of particles within the rings with its wide and narrow angle cameras Voyager 1 was able to take a series of pictures showing in incredible detail Prometheus acting
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as a shepherding moon to the FR ring and Atlas as a Shepherd to the a-ring this first Voyager craft was also sent by the team at NASA's jet propulsion laboratory to investigate one of Saturn's most intriguing moons up close for the very first time Titan had already been identified as potentially the only moon in the solar system with a thick Earth earthlike atmosphere and Voyager was set on a course that enabled it to pass by Within just 6,400 km of its surface as it flew on
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the Dark Side of the Moon looking back at Titan's atmosphere through the haloed light of the sun it was able to accurately measure for the first time the density composition and temperature of the atmosphere and also obtain a precise measurement of Titan's Mass this mysterious moon the largest of all Saturn satellites was found to have an atmosphere almost entirely composed of nitrogen just like the Earth with a surface pressure just 1.6 times that of our planet Voyager opened our
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eyes to this curious world for the first time a world we would come to explore in even more detail with the Cassini haan's Mission which would touch down on the surface of Titan as well as exploring the Rings and moon systems of Saturn Voyager was able to deploy its array of sensors and cameras on the planet itself with its closest approach on the 12th of November 1980 Voyager came within 77,000
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Mi of the saturnian cloud Toops and was able to measure powerful winds traveling at 1,1 100 mph whipping around the planet's equator and Aurora but most intriguing of all was the discovery that Saturn's upper atmosphere was composed of only 7% helium while the rest was mostly made up of hydrogen scientists had expected Saturn to have the same atmospheric helium levels as Jupiter and the Sun at 11% so this much lower level suggested something intriguing was going on deep
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within Saturn's internal structures where was the missing helium the lower levels in Saturn's upper atmosphere suggested that the heavier helium might be slowly sinking through Saturn's hydrogen but it would take the arrival of Voyager 1's sister craft 9 months later to enable scientists to further probe the inner workings of Saturn and to begin to reveal the fate of the rocky ice world that had been lost inside this planet billions of years earlier while passing behind
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Saturn and so shielded from the view of the earth Voyager 2 used its radio science system to probe Saturn's upper atmosphere gathering information on its atmospheric temperature and density it was ingenious dual use of its telecommunication system that allowed Voyager to create a temperature profile of the planet that provided the first direct evidence of something that scientists had long suspected at the uppermost level of its atmosphere Saturn's temperature was 70k
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minus 203° C while at the deepest levels around 120 kilopascals the temperature increased to 143 K minus 130 C Saturn it seemed was emanating far more heat than it was receiving from the Sun this was a planet with a mystery at its heart but Voyager was about to gain an even more beguiling insight into Saturn's inner workings in August 1981 as the Voyager 2 probe passed over the North
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Pole of the planet it took a series of images with its two camera Imaging systems that would reveal an extraordinary secret sitting on Saturn's Crown Stitch together the images and analyzing the data from this distant probe David Godfrey and a team from the national Optical astronomy observatories in Tucson Arizona were able to piece together a startling image of a storm system unlike anything
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ever seen anywhere in the solar system first published in 1988 7 years after Voyager 2 had left the saturnian system the patchwork image revealed a puzzling hexagon shaped weather pattern sitting around the planet's Northern pole each of the six sides of this vast storm system is around 14,500 kilm in length 29,000 km across and at least 300 km high it's so vast the Earth could fit into it
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at least four times over and it's not just the scale of it that's breathtaking swirling inside it are winds whipping around at speeds of over 320 kmph and the whole hexagonal storm is completely rotating every 10 hours and 39 minutes this is a storm on an unimaginable scale and 30 years later it still rages on but despite multiple hypotheses the atmospheric Dynamics behind its shape remain a mystery as the seasons changed and spring arrived in the northern hemisphere towards
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the second half of the mission we got the chance to look at the hexagon that surrounds Saturn's pole if you flattened it out it would be about 2 Earths wide Saturn itself is about 10 Earths wide so this is a major feature and it's basically a jet stream every time we posted a picture of the hexagon on our website the hits went through the roof because I think people were so amazed that you could have something in an atmosphere that had straight sides to it Carolyn Porco Cassini
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mission from our Vantage Point here on Earth it looks as if our atmosphere stretches on and out forever and yet by the most widely held definition it takes a journey of just 100 kilm to officially make your way through the atmosphere and into space of course atmospheres don't just stop dead the Earth's atmosphere gradually recedes with increasing altitude becoming progressively thinner until by the time you get 100 km up you'll have 99.9 9997 of the atmosphere below you
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this essentially arbitrary line between the Earth and space is known as the kman line it's a line that was calculated by the Hungarian American engineer and physicist Theodor Von caran to be the altitude at which the air becomes simply too thin to support aeronautical flight where as he wrote aerodynamics stops and astronautics begin cross this line and you have a officially gone from being a pilot to an astronaut and you get to join a club that still only contains 561 members
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at the time of writing the number of humans who have made it over the line is still so small because traveling the short hop into space might be slight in distance but it is large in terms of the power and Technology needed to lift anyone or anything that far from the Earth's surface gravity binds us tight to our little rock and despite over 60 years of space travel it means almost all of us are still very much rooted to the ground the reason we find it so tough to leave the
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Earth is because of the mass of the planet all 5.9 sextilion tons of it which creates a gravitational pull so strong it requires an escape velocity of around 11186 km/s to make it Off the Earth and into space that's a lot of speed to counteract the 99.8 m/s squ squ of gravitational force that is continually tugging us down gravity keeps our species firmly locked to the surface of the planet
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but it also keeps a tight grip on everything else on the surface of the Earth be it solid liquid or gas including the 5.5 quadrillion tons of nitrogen oxygen carbon dioxide and other Trace gases that together make up the Earth's atmosphere in the very simplest terms the size of the atmosphere of any planet is intricately linked with the mass of that planet the bigger the mass of a planet the greater the attraction of gases to its surface but that's not the end
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of the story The ability of a planet to retain an atmosphere is also dependent on a multitude of other factors including the composition of the atmosphere its temperature proximity to the sun geological activity the ability of the planet to protect itself from the ravages of the solar wind and finally the impact of life itself which has seen our atmosphere gradually pumped full of oxygen it's the intricate balance of these factors that dictates the endurance and
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composition of the gases around the planet each one a unique atmospheric fingerprint fast forward through the history of the solar system and we see a familiar theme again and again around the inner rocky planets each of the four planets grabbed onto a thin atmosphere but then the individual characteristics of each planet set in motion its own individual Evolution Mercury the smallest of the planets and closest to the Sun lost its atmosphere long ago with only the mest Wisps
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remaining today next there is Earth sitting in the goldilock glow of the sun we have clung on to our 100 km of atmosphere in one form or another for billions of years allowing life to thrive under its warming Embrace Venus on the the other hand despite starting with an atmosphere likely very similar to our own has now choked on the 250 km deep toxic atmosphere that blankets its surface today each of the four rocky worlds has seen its atmosphere EB and flow over time but no matter
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what twists and turns the story of each planet may have taken there has always been and will always be a limit to the size that any atmosphere can grow around these relatively small lumps of rock before we return to Saturn to understand how its atmosphere grew in a very different way to those of the rocky planets we should take a swift look through the history of the Earth's atmosphere in more detail to establish how it began and evolved using a combination of
2:10:09
geology climatology and paleontology scientists have been able to piece together an immensely detailed picture of the Earth's atmospheric Evolution far back in the Earth's history a very different type of atmosphere to the one we see today surrounded the primordial Planet the newly formed Earth had grabbed onto gases from the billowing Vapors of the solar nebula The Cloud of gas and dust that the planet had formed from consisting almost entirely of hydrogen and
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simple hydrogen-based molecules such as water H2O methane CH4 and ammonia NH3 this primary atmosphere would have been entirely created by the capture of the nebulus gases by the gravitational attraction of the planet slowly over time the composition of the atmosphere changed from a hydrogen-based one to one rich in nitrogen and carbon dioxide we think this shift to the secondary atmosphere was at first triggered by the giant impact of the planetesimal Thea on the early
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Earth and then driven by a combination of gases produced during the late heavy bombardment while asteroids rained down on our planet for millions of years and the geological activity within the Earth sent vast quantities of gas upwards through all-encompassing periods of volcanism by the time first life appeared on the planet the nitrogen Rich atmosphere was stable but gradually as life
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took hold a new component would begin to appear in the Earth's atmosphere 2 and a half billion years ago photosynthetic life had become so prevalent it triggered a Tipping Point known as the great oxygenation event event during which oxygen was produced by living things at such a rapid rate it far exceeded the amount of oxygen that was captured from the atmosphere in Earth's geological chemical reactions the result of this shift to the third atmosphere has been the presence of
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free oxygen in our atmosphere ever since providing the energetics to support the rapid evolution of life on Earth and of course one of these life forms has become so dominant we've developed a way of life that is now fundamentally changing the atmosphere of our planet for a fourth time but not for good now with this history of our planet's atmospheric evolution in mind let's return to the earliest days of the solar system and explore the very different path taken by
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Saturn around 4 and A2 billion years ago the young Saturn had grown to become one of the largest Rocky bodies in the history of the solar system at least 10 times the mass of the Earth it found itself far beyond the warmth of the sun locked in its icy orbit a frozen Rocky world on a scale unlike anything we've ever seen but time would not stand still for this world having grown as large as it could from Rock and Ice alone its Barren surface would not stay lit by the
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dim light of the Sun for long as it continued to grow Saturn would become a radically different kind of planet defined not by its Rocky surface but by an atmosphere that would bury it beneath vast volumes of gas an atmosphere that would not just enwrap the planet but engulf it just like the Earth in its earliest days as Saturn continued to grow it drew not just solid material but also gas towards it from the vast clouds swirling around the embryonic solar system huge amounts
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of the hydrogen and helium left over from the formation of the sun clung to the vast Planet creating a first atmosphere that may well have been very similar to the earliest one on Earth but Saturn's early atmosphere would follow a very different course as it was driven by two key differences between the young worlds first Saturn had grown far far bigger than Earth so by gravitational attraction alone the volume of gas it could attract towards itself was far greater
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than anything the diminutive Earth was able to but it wasn't just size that drove Saturn's atmosphere to grow so rapidly located this far from the Sun the freezing temperatures meant that even the most volatile of gases could cling onto the planet without being driven off by The Heat Of The Sun hydrogen helium ammonia methane and many other gases that were too light for the smaller worlds of the inner solar system to hold on to were able to accumulate out here with Saturn's
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vast mass and the freezing temperatures being enough to draw the in trillions upon trillions of tons of gas began to envelop the planet reaching depths first of hundreds of kilometers and then thousands and as this new atmosphere grew it transformed the surfaces Below on Earth under our canopy of air it's easy to forget that all of those molecules sitting above your head right now have a weight if you draw a 1 cm square on a piece of paper at sea level and imagine a
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column of air stretching all the way up from the square to the top of the atmosphere it will have a mass of on average just over 1 kg exerting a downwards force of 10 Newtons onto the paper a pressure that we call 100 kilopascals or one bar that might not sound like much but all of that weight reveals itself in the subtle and not so subtle effects of atmospheric pressure that we can see all around us for example the simplest of classroom experiments can reveal the power of
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the atmosphere by the process of just removing the air from a plastic bottle the bottle collapses not because of the vacuum that it creates but because the bottle cannot withstand the pressure of the atmosphere that is pushing down on it while 100 kilm of atmospheric pressure can quickly crush a bottle here on Earth a much bigger atmosphere can exert pressures that not only are able to sh shape
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things on the surface but also have the power to transform an entire planet and that's exactly what we think happened to Saturn 4.5 billion years ago as its atmosphere deepened the thousands upon thousands of kilometers of gas weighing down on its surface began to generate incredible pressure heating The Rock and ice so much they began to Glow it's thought perhaps that for a brief moment in time the Heat generated on the surface of Saturn by these extraordinary pressures meant
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that the glow of the planet even outshone the Sun but this was just the beginning as Saturn matured the pressure at its core grew to 10 million times the level we experience on Earth at that level of pressure matter behaves in extremely strange ways and the Very idea of a planetary surface becomes meaningless as Saturn took on its new form the enormous pressures generated crushed and melted its solid core destroying the rocky World it had been and replacing it with a new
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world utterly alien in its characteristics Saturn had transformed from a world of rock and Ice into a wholly different class of Planet a gas giant a ball of gas so big it could contain 800 earth-sized worlds inside it making it the second largest planet in the solar system after Jupiter at 7:55 and 46 seconds a.m. eastern daylight time on the 15th of September 2017 NASA's deep space Network antenna complex in cber Australia received notification that contact had
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been lost with one of our greatest Space Explorers after 13 years of extraordinary encounters the Cassini spacecraft had made its last fateful maneuver plunging head first into the atmosphere of Saturn 45 seconds later the craft would be gone crushed by the atmosphere of the planet it had spent over a decade so carefully exploring its last image a monochrome view of the planet's night
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side lit by the reflected light of the Rings was a picture of its own grave revealing the location towards which the spacecraft would plummet in its final Act of self destruction as it entered the planet's atmosphere just a few hours later this was the end of a 20-year mission that had exceeded all expectations the forth spacecraft to enter the saturnian system following after Pioneer and the voyagers Cassini was the first to live there ultimately spending 13 years and 76
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days in orbit around Saturn during this time it explored the planet its rings and its moons and relayed images and and information in a level of detail that would change our understanding not just of the saturnian system but of the whole solar system and our place within it it All Began on the 15th of October 1997 at Cape Canaveral with the launch of the spacecraft aboard a mighty Titan 4 rocket to get to this moment had taken the best part of 15 years the combined efforts of 28
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countries and a budget of $3.26 billion but even then it would be another s years before Cassini could truly begin its mission objectives getting this 5.5 ton machine across 1.6 billion kilm of space would require a complex trajectory that would take it on two flybys of Venus and out to the asteroid belt before returning to the Earth 2 years after takeoff for a final slingshot from its home planet that would send the craft hurtling at speeds of 98,3 46 m per hour outwards past
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Jupiter and on towards its final destination this complex and high-risk trajectory was designed to exploit the orbital momentum of Venus Earth and Jupiter to enable the spacecraft to accelerate which helped keep the amount of fuel and hence the launch weight to a minimum while making sure the craft could pick up enough speed to complete its Epic Journey however the tradeoff of using this vve JG a Venus Venus Earth Jupiter gravity assist trajectory was a nervous 6-year 261
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day wait for the team back on Earth as the craft made its convoluted voyage across space primary Voyage complete Cassini now faced the life or death challenge of slowing itself down with enough Precision to enter orbit around Saturn the tiniest miscalculation would have seen billions of dollars flung into the outer reaches of the solar system and Decades of work lost forever on the 30th of June 2004 the spacecraft began its complex Saturn orbital insertion s SOI
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maneuver by flying through the gap between the f and g Rings this maneuver alone was not without serious risk from the potentially devastating impact of particles in the Rings colliding with the craft so Cassini had to carefully Orient itself to protect its instrumentation once through the ring plane the spacecraft had to rotate itself once again to point its engine directly along its
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flight path so that when the engine fired it would decelerate the craft by a precise velocity 622 m/s allowing it to fall into the gravitational hand of Saturn decelerate too much and the craft would fall into Saturn too little and it would fly off into outer space at 8:54 p.m. PDT Cassini was finally captured by the gravity of this gas giant becoming the first spacecraft to ever orbit Saturn a new age of exploration had begun and over the next 13 years Cassini would
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provide an extraordinary return on investment the voyagers and Pioneer had given us our first rough glimpses of Saturn's moons but during its 13 years in orbit around the planet Cassini did so much more not only did it discover a whole host of new moons it also helped solve countless Mysteries around moons we already knew existed such as Titan and Enceladus and revealed just how varied the characteristics of the 60 plus moons of Saturn really are Cassini also allowed us to study
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for the very first time the interactions between Saturn's managerie of moons and the ring system within which they sit as well as the structure and history of the Ring system itself one of cassini's key mission objectives was to explore the characteristics and activity of the vast atmosphere that makes up most of Saturn Voyager 2 had revealed the presence of a heat Source buried deep beneath the planet's Cloud tops that seemed to be producing vast amounts more energy up to 87%
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more in fact than the planet absorbs from sunlight but what was the source of this heat and how did Saturn's immense atmosphere organize itself into the vast and intricate weather systems like the huge hexagon this remained a question that Cassini was charged with solving atmospheres can be some of the most spectacular and complex environments found on any planet from the crushing intensity of
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Venus's choking atmosphere with its raging winds and sulfuric acid rain to The Thin Blue Line of Earth where even on our somewhat milder planet we see endless storm systems in the inner solar system the atmospheres of the rocky planets and the weather systems they contain are all powered by a single Source the Relentless Heat Of The Sun all the weather we see on the rocky planets whether it's a dust storm on mars or a hurricane on Earth are driven by the same simple process it
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begins with the sun beating down onto the planet's surface heating the ground which in turn radiates back heating up the air closest to the ground that air expands which means it becomes less dense and so the hot air closest to the ground Rises the result of all this Rising air is that you get thermals energetic movement of air from the ground into the upper atmosphere over the oceans exactly
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the same process occurs with the heat of the sun evaporating vast amounts of water and lifting it up into the atmosphere so in the very simplest terms all of the extraordinary weather we see on Earth or any of the other terrestrial planets is driven by the sun heating the land and sea and causing the air to move around travel further out into the solar system however and the character of any atmosphere radically changes the storms on Saturn are among the most violent found
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anywhere in the solar system generated by Rich complex and Powerful weather systems we've been witnessing these giant storms from far for almost 150 years Assaf Hall the Great American astronomer and discoverer of the two moons of Mars was the first to observe one of these storm systems back in 1876 looking through the largest refracting telescope of the time the United States Naval Observatory 66 cm telescope located in Washington DC he was able to make out a Great White Spot
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sitting in the northern hemisphere of the planet at the time Hall wouldn't have known much at all about the phenomenon he was looking at it was intriguing simply because it enabled him to make the first estimate of the rotational period of the planet over the following decades however this great white spot was observed again and again roughly falling into an appearance every 20 to 30 years before slowly fading away fortunately for us the long gaps between each appearance were
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cut short in December 2010 when a Great White Spot appeared just 4 years after the previous one this time with the Cassini probe in orbit we had the opportunity to track the evolution of one of these storms close up from its birth in early December 2010 to its disappearance 8 months later this vast storm system resembling in many of its characteristics a simple thunderstorm here on Earth emerged as a single White Spot 1 1,300 km from top to bottom and 2,500 km from side to
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side over the ensuing months Cassini was able to follow the storm as it stretched out around the planet just a few weeks after its formation the tale of the storm had extended across 100,000 kilm and within 6 months this great storm had stretched so far it encircled the whole planet Cassini was able to image directly for the first time lightning occurring in the middle of this giant storm in broad daylight the fact that the lightning could be detected on the day side of the
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planet surprised the Cassini team and suggested that the lightning must be particularly intense to make it visible in such bright light the lightning flashes are comparable to the strongest lightning flashes that we see on Earth that was a joy just to finally witness lightning on Saturn and we could tell that it was coming from the cloud layer the deepest Cloud layer which is about 60 Mi down
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and is the water Cloud the water ice cloud and that makes sense because lightning is produced on Earth because of updrafts and particles being elevated through an atmosphere Rising through an atmosphere because they're convecting we had a whole variety of scientific goals at Saturn and one of the main ones was to understand the meteorology of the Saturn atmosphere and what energizes the winds that we see on it and so on and we have affirmed now the belief that the
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atmospheric systems on Saturn are actually powered by energy from below from an internal source on Saturn they're not powered by sunlight like we have on Earth carollyn Porco Cassini Mission Cassini was also able to turn its cameras onto the giant hexagon structure that Voyager 2 had first photographed over 30 years before this time with its highdefinition narrow angle cameras trained on the enormous feature around the North Pole of the planet Cassini was able to capture the
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giant hurricane-like storm in extraordinary detail this vast Vortex was measured as 2,000 km across at just the eye of the storm and with Cloud speeds traveling at over 150 m/s it's rotating far faster than any hurricane we've ever seen on Earth exactly what causes this or any of the giant storm systems we've witnessed on Saturn is still not fully understood but one thing we absolutely do know is that this far out from the Sun these weather systems cannot be driven primarily by by
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the sun's heat with Saturn receiving 100 times less of the sun's energy than Earth something else must be driving its weather something that creates the same great up swellings of heat we see on Earth but that on Saturn is entirely generated from the interior of the planet as yet we've not been able to peer deep enough into Saturn's interior to see directly what happens inside this strange world but in the last couple of years we've come closer than ever as we've accumulated
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evidence from Pioneer Voyager and of course Cassini and combined it with our increasingly sensitive groundbased observation we've been able to start piecing together a detailed Journey Into the Heart of the planet by just touching the cloud Toops of Saturn alive with great storm systems and flickering with immense bolts of lightning they have given us the first hints of the truly strange world that must lie beneath and the Mysterious energy source that brings this planet to
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life our journey deep into the interior of Saturn begins not with clouds but with rain at the very outer edges of its atmosphere in the space between the closest ring the d-ring and the planet itself we've discovered the phenomenon of ring rain an endless downpouring of material falling from the Rings into the upper atmosphere of the planet below we know this because as Cassini took its
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final fatal plunge on the 15th of September 2017 it flew through this Uncharted no man's land and was able to make the first direct measurements of the rain falling from the Rings using the ion and neutron Mass spectrometer it measured the rate at which the rain was falling from the Rings a staggering 10,000 kg of material every second it was also able to reveal that the ring rain is comprised of a mix of hydrogen water ice and a surprising quantity of complex organic
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compounds like butane and propane all showering down onto the planet and changing the chemistry of its upper atmosphere in ways we are only just beginning to understand Cassini then began its final historic dive into the upper atmosphere of Saturn struggling to keep its antenna pointing towards the Earth as it was buffeted by the increasing turbulence while continuing to send a stream of precious data back to us right until the very end traveling at around 123,000
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kmph Cassini entered Saturn's upper atmosphere at 33050 PDT 1,900 km above the planet's Cloud Tops This was the first time scientists had ever been able to sample the atmosphere directly our distant human Envoy touching the gas giant for the very first time over the next few seconds Cassini increased the use of its altitude control thrusters to steady its rapid descent into the thin outer reaches of Saturn's atmosphere and keep the antenna pointing towards Earth for
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a final few seconds of contact but this was a losing battle over the next minute and a half the growing density of the upper atmosphere rapidly began to increase the friction on the forward-facing surfaces of the spacecraft raising the temperature at high speed and creating an unfolding thermodynamic situation that Cassini had not been designed to withstand at precisely 330 PDT 1,500 km above the cloud tops Cassini finally lost its battle for control after 20
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years in space 13 of which were spent exploring Saturn and having traveled a distance of 7.9 billion kilm this battered explorer was no longer able to maintain a stable flight path through the increasingly dense atmosphere beginning to Tumble and roll the last few bites of data left its antenna streaming the 90-minute journey back to Earth and the mission was long over before that final contact reached our planet precisely what happened next to the little spacecraft as it
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fell into the grip of this giant planet remains no more than well-informed conjecture using computer models to predict its final seconds the Cassini team were able to watch only in their Mind's Eye as the craft tumbled chaotically through the atmosphere traveling at 144,00 km hour just 1,100 km above the cloud tops and with temperatures rapidly increasing every component of this unprotected machine began to disintegrate with all Computer Systems Failing and the spacecraft blind
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and deaf to its surroundings it began to break up its gold insulation blanket rupturing first before the external carbon fiber structures of the spacecraft itself began to fracture and frag M then with the Rings gleaming in the sky above it and the yellow Cloud tops beckoning below what was left of Cassini stre across the saturnian sky blazing with temperatures higher than the surface of the Sun the gas tanks of propellant that helped steer The Craft on its epic Voyage
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blasted apart the remaining structures into a million different pieces which in a final spectacular moment lit up a little corner of the Majestic planet with the burning debris of its greatest Explorer Cassini was dead but its final Journey was far from over over the following minutes the Deb scattered and fell through the cloud tops deep into the planet's interior until finally the atoms of this beloved machine built by human hands millions of kilometers away on a
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far away world came to rest in the heart of the planet Cassini and Saturn Inseparable forever more
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where the debris of Cassini finally ended up we can only imagine but the data from this extraordinary mission that was collected right up to its very end has helped us to dive deeper into the detail of Saturn's interior than ever before as the wreckage scattered and fell from the upper atmosphere it would have fallen through the very first Cloud tops of the planet here with temperatures ranging from -170 to -110° C the clouds are made not of water ice but Frozen
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ammonia it's these ammonia ice crystals that give Saturn its characteristic pale yellow color a color that we can see shining back at us with even the most modest of Earthbound telescopes Beyond this upper layer of cloud as the pressures begin to increase and the temperature rises huge clouds of water ice form a thick layer the water molecules perhaps long lost remnants of the building blocks of the icy world that Saturn once was it's here amongst the vast Cloud systems
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that lightning more powerful than anything we see on Earth illuminates the sky within storm systems that rage for months on end Cassini gave us the first still and moving images of these lightning storms and enabled us to predict the next great transformation that will happen within the planet's interior every couple of decades Saturn surprises us and breaks into a fit and actually erupts with really major storms these are Global storms and they last for about 6 months to a year
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the one that we saw with Cassini in 2010 was so powerful that our calculations show it was the most powerful storm we've ever seen anywhere in the solar system even Jupiter in terms of its Central conductive storm system we had an amazing chance to see that during the Cassini Mission and then when we looked at those clouds that it was forming we found amazing things in the cloud in the storm clouds of Saturn we found that it had water ice and this really blew our
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minds because water should be sequestered deep down in the atmosphere you should not find it at the top of the atmosphere it only gets there when you have huge convective updrafts and we're talking updrafts that bring gas up from 100 Mil down and on the earth we only see gas going up and convection going up only about 10 mil here you have storms 10 times bigger very powerful stor storms lifting things up from 100 Mil down and bringing up the water from
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below which was probably actually a mixture of gas and water but then it brought it up and it turned into ice and the component of water ice in it really shocked us Kevin Baines Cassini Mission we now think that around 100 km below the visible atmosphere the same distance from the surface of Earth to space with temperatures inside Saturn's lightning reaching almost 30,000 de this lightning transforms methane gas in the atmosphere into huge clouds of carbon soot
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carried higher into the atmosphere on great convection currents we think that it's these specs of carbon producing lightning that can explain the mysterious dark clouds that Cassini was able to observe and image over many years this particulate matter rains down from the upper Cloud layers until at a depth of 1 ,500 km we think the enormous pressures begin compressing this soot into graphite which then Falls further into the depths of the planet we then think that at
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around 6,000 km down this graphite under goes a truly extraordinary transformation with pressure and temperatures rapidly increasing the graphite is compressed into solid diamond that rains down for at least 250,000 km estimates suggest at any one time 10 million tons of diamond hail is raining down within the planet from specs of diamond dust just a millimeter across to chunks as big as 10 cm perhaps even for a brief moment in time some of the charred carbonized remains
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of the Cassini probe made it down into these depths and transformed into diamonds as well falling further into the planet it had helped us understand but eventually even these diamonds will ultimately succumb to the enormous pressures of Saturn's interior around 30,000 km into the atmosphere where temperatures reach 8,000 de C the diamond melts and forms liquid Diamond raindrops that continue to descend into the abyss it's here around 40,000 km down into
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Saturn's interior that we believe the source of Saturn's energy the energy that drives all the storms and weather we see playing out on its surface is finally revealed here the pressures are so intense that the hydrogen that makes up over 96% of Saturn's mass is compressed into a vast ocean of liquid hydrogen that is saturated with helium gas under these enormous temperatures and pressures the helium precipitates out and Falls like rain through the ocean depleting
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the levels of helium in Saturn's outer layers which explains the lower than expected amount of helium first measured by Voyager 1 in 1980 it's a process that through the simple action of friction as the molten helium rain falls creates an incredible amount of heat and we think this is the engine the energy source that helps power Saturn's ferocious weather and drives its entire atmosphere for tens of thousands of miles in every direction finally
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we reached the interior of Saturn a layer where the liquid hydrogen is so compressed it starts to behave like a liquid metal and the helium itself May accumulate into a metallic shell surrounding the core Beyond here we do not know if a rocky core remains as a remnant of Saturn's long lost past or whether under these enormous pressures the possibility of solid rock is no longer viable whatever lies at the center of Saturn we estimate that the this core region
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has a mass of around 20 times that of the earth and a diameter of around 25,000 km and here perhaps a few tiny fragments of Cassini might have come to rest in the ancient heart of the planet Saturn has lived a life of incredible drama the evolution from Rocky beginning to the extraordinary gas giant we see today took just a few hundred million years of rapid transformation and yet throughout almost all of this time one thing has been missing we now think Saturn was
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born naked and has lived out the vast majority of its existence without the structure that makes it more iconic than anything else Saturn is a world defined by its rings ask a child to draw a planet and more often than not they'll draw something that looks remarkably like Saturn the particles in the rings of Saturn are almost impossibly delicate and intricate most of them are no bigger than snowflakes but some are as large as houses orbiting the planet at 1,800 km hour in
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one of the most beautiful structures we have ever laid eyes on one of the reasons why the Rings have captivated us for so long is that despite their vast distance from the earth if you look through a simple telescope they shine back at us bright against the night sky reflecting the Sun's light as powerfully as the planet itself for years the age and origin of the Rings has been argued over with conflicting evidence supporting two very different hypotheses on one side the argument
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has been made that a ring system as dense as Saturn's must be an ancient structure shaped from the remnants of the planet's formation on the other side of the fence the evidence has been used to suggest that the Rings must be youthful a relatively recent addition to the ancient Planet the brightness of the Rings is not only beautiful but also rather surprising the solar system is not a very clean place in fact it's full of dust and dirt and so we would expect any ice crystals that
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hang around for any length of time to inevitably get dirty we also know that if ice gets dirty it doesn't reflect sunlight anywhere near as brightly so in the case of the Rings we would have expected if they had been present over the lifetime of the planet all of those particles and blocks of ice would have become increasingly less reflective if they had formed anywhere near the birth of Saturn
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they would almost certainly be invisible to us now or at least incredibly faint and yet they shine brightly as if they were made just days ago variations of this debate have been rumbling since the 18th century but that all changed with Cassini during its 13-year tenure around the planet the probe was able not only to see Saturn's rings like never before but also provide us with direct evidence about their density and composition and this information is helping scientists to solve
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the puzzle of the Rings once and for all for the very first time Cassini was able to take physical samples directly from the Rings and surrounding dust using the cosmic dust analyzer CD a mounted on its exterior this highly sophisticated piece of technology is basically a multi-million dollar bucket but a bucket that can detect particles 1 millionth of a millimeter wide that's smaller
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than a virus and determine the particle size speed and direction of travel as well as their chemical composition by measuring the dirt and dust from the Satan system falling onto the Rings Cassini has allowed scientists to rewind the clock on the Rings and provide direct and compelling evidence that the ice particles are nowhere near as Dusty as they would be if they were an ancient part of
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the planetary system this confirms the long-held belief that the Rings are so bright because they are young and in fact the evidence gained from Cassini CDA suggests they are far younger than we ever imagined latest estimates suggest they're somewhere between 10 to 100 million years old that's nearly 4.5 billion years younger than Saturn itself so where did they come from once again Cassini provided a tantalizing clue in its final few days Cassini embarked on a series of
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almost Reckless orbital trajectories that were so risky to the spacecraft's safety they would never have dared to be attempted earlier in its Mission taking the probe closer to the planet than ever before the team flew Cassini repeatedly through the gaps between the upper atmosphere of the planet and the inner Rings throughout September 2017 as it performed 22 of these perilous Dives Cassini was able to take measurements of the gravitational tug of both the planet and the
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Rings this data was then used to calculate the mass and density of the most substantial ring in the saturnian system the B ring makes up 80% of the mass of all the Rings and yet cassini's measurements suggest sugested that the total mass of the Ring was surprisingly low this result although not conclusive strongly points to the fact that the Ring's Origins lie not in the ancient past during the formation of the planet itself but to a far more recent and dramatic event
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involving one of the worlds trapped in orbit around it the Rings it seems were born of a moon Saturn has 62 large moons and countless smaller ones that range in size from planetary scale objects like Titan to smaller irregular lumps of rock like Eon and we're still hunting for new moons to add to the list on its travels Cassini spotted two objects within the fing that are potential candidates for Moon Hood but as yet s stroke 20004 S6 and sroke 20004 S3 remain
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unverified and unconfirmed within this managerie of worlds are an endless variety of Clues written into the size form and surface features of the moons that allow us to read the history of the saturnian system revealing the often violent and volatile events in its past mimas is otherwise known as the Death Star Moon and was first spotted in 1789 by William herel who is immortalized in Mass's eponymous huge impact crater myass is just 396 km across and the Hershel crater covers 130
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km of that surface a deep scar that tells us that once long ago there was a giant impact that almost destroyed the moon iapetus the third largest of Saturn's moons at 1,500 km across is almost planetary sized and has a distinctive two-tone coloration Half Light and half dark iapetus was discovered by Giovani Cassini himself in 1671 and has another distinctive feature that we have long puzzled over running around 3/4 of the moon's diameter is a massive equatorial Ridge it's
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one of the highest mountain ranges in the solar system 20 km from the Peaks to the ground below and it's thought this may have formed because a ring that once circled the moon collapsed onto its surface Hyperion is the strange sponge-like Moon that tumbles around in Saturn's orbit which in 1848 was the first non-spherical moon ever to be discovered to this day it remains a mystery as
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to what caused its punctured surface and irregular shape and it's been suggested that Hyperion is in fact a remnant of another Moon that broke up long ago Pan the small Walnut shaped Moon that was discovered less than 30 years ago from the analysis of images is taken by the Voyager 2 probe is named after the Greek god of shepherds it's so named because pan is a Shepherd Moon clearing the orbit of the anchor Gap a 325 km space within the a-ring it's distinctive equatorial Ridge is
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thought to be made of material that's been swept up and accumulated as it clears its path through the ring cassini's endless stream of images and data until 2017 has enabled scientists to analyze each of the moons in ever more detail and it's become increasingly apparent that they are intimately linked with the ring system they orbit many of the moons are made of exactly the same material as the Rings themselves mimas iapetus and Hyperion are ice moons composed almost entirely of
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Frozen water ice with only the smallest amounts of rock in their makeup from the evidence that we've been able to read on their surfaces it seems almost certain that through 4 billion years of violent interactions at least some of the moons of Saturn must have both come and gone over the planet's history all of this begins to point us towards the idea that perhaps the most intriguing moon in Saturn's long history is one that is now entirely missing around 200 million years ago as
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dinosaurs roamed the Earth we now believe a long lost Moon orbited close to the planet Saturn a moon Mo perhaps 400 km across and formed almost entirely of ice this was a doomed World orbiting too close to resist the immense pull of Saturn's gravity its fate sealed at the moment of its birth it was the French astronomer and mathematician edir Ros who first suggested the existence of this
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long lost moon in 1848 he christened it Veritas after the Roman goddess of Truth who according to Legend is supposed to have hidden in the bottom of a holy well rash had postulated the existence of this Moon while exploring a particular Dynamic of celestial mechanics that describes the potentially violent gravitational relationship between two celestial bodies he was able to demonstrate that when a moon moves within a certain distance of the planet it is orbiting it can cross a
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threshold where the force of gravity is so strong the moon will be ripped apart this distance has become known as the rash limit and is dependent on many factors including the mass radius and physical characteristics of the Moon and planet outside of the rash limit a moon can exist in happy equilibrium with its Planet orbiting in the gravitational grip of the larger body while maintaining its physical Integrity but if that same moon's orbit degrades to the point where the
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rash limit is crossed the tidal forces exerted on the moon exceed the gravitational attraction that holds the moon together in a sphere resulting in the moon's destruction this relationship applies to any Moon Planet system including our own here on Earth we see the relationship between our planet and moon on a twice daily basis as the tides e and flow across the planet these tides are caused by the difference in the gravitational pull of the moon from one side of the Earth to
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the other and that difference although subtle is powerful enough to move entire oceans with the forces of tidal gravity just as the moon creates tides on Earth so the Earth also has a tidal effect on the moon and because the Earth is much greater in mass that effect is more powerful than you might think the Earth's pull is in fact powerful enough to deform the moon's surface even today it causes Moon tides on the lunar surface where it causes the rock to rise and fall but
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the effect was even stronger 4 billion years ago when the moon was nearly 17 times closer to the Earth back then the pool from our planet caused a tide of solid rock to Rise and Fall by many meters and if the moon had ever come any nearer it would have crossed the rush limit and been ripped apart when edar Ros first formulated the equations calculating this line he realized that the result of such destruction would not just be the obliteration of a moon but also the creation
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of millions upon millions of fragments the debris of the Moon orbiting around its Destroyer he also deduced that in time these fragments would form once again into the most delicate of structures a system of rings under the influence of the planet's gravity in one of the more gruesome Tales From classical mythology Saturn the Roman god of time and harvest actually e five of his newborn babies to prevent them taking his power now Cassini has shown us that at least metaphorically
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speaking they weren't far wrong we now think that 10 to 100 million years ago just beyond the outer reaches of Saturn's vast atmosphere an icy Moon orbited gradually edging closer and closer to that Tipping Point the rash limit as Saturn's immense gravitational force pulled at it this great Moon began to rupture and in a moment undoubtedly Worthy of even the greatest of mythological stories up to 30 million trillion tons of ice more than 30,000 times the weight of
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Mount Everest broke apart in orbit and spread out around Saturn traveling at tremendous speed around the planet it's likely that this debris quickly scattered to encircle the giant planet and in the space of no more than a few days Saturn's iconic Rings had been born today this giant ring system has evolved into the intricate structures we can see in the night sky Saturn's powerful gravity has
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helped keep its near perfect elliptical shape but an endless series of collisions have caused it to gradually flatten out now this debris forms a dis wider than Jupiter yet on average just 10 m thick with moon-sized chunks of ice orbiting through this structure great voids have been cleared turning one ring into many in places moons have pulled particles of ice upwards to create strange
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Peaks over a kilomet high which cast spectacular Shadows across the Rings Saturn once a tiny world of rock and Ice a world that has undergone repeated Transformations has today become the Solar System's greatest Jewel and Cassini our most Intrepid of explorers has forever deepened our understanding of the life story of this planet yet Perhaps cassini's greatest gift is not in its Revelations of the past but in the Glimpse it has given us of the future because just beyond
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Saturn's rings Cassini would discover a hidden treasure a world that may hold answers to some of our deepest questions about our place not just in the solar system but in the [Music] universe one of the unmistakable jewels of the saturnian system is Titan a giant it is the second largest moon in the solar system and this planet sized satellite is larger than the smallest planet Mercury and 50% bigger than our own solitary moon discovered by Dutch astronomer Christian haens in
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1655 it has held its Secrets close for Centuries cloaked by thick clouds the only moon in the solar system with a dense distinct atmosphere of its own from afar Titan hinted at being far more like a planet than a moon it would take a mission of breathtaking ambition to finally peer under her veil and see the Wonders that lay beneath on Christmas Day 2004 after a 7-year journey across the solar system the Cassini probe released its sibling craft hens setting it off on a 4
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million km path to Titan simple in appearance haens looked as if it borrowed its design from the classic cartoon UFOs of the 1950s but nothing was simple about haens this was a highly Advanced spacecraft about to begin one of the most complex Maneuvers ever attempted in the history of human space exploration as it made its 3-we Journey towards Titan the team of Isa European Space Agency scientists who had dedicated a lifetime's work to the project watched on hopeful but
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helpless from the moment of release they had lost Direct Control of the probe and were unable to send it commands instead as planned in the mission protocol haggens was now entirely controlled by the onboard autonomous computer systems all they could do was watch and wait to see if haggens could fulfill their Ambitions by becoming the first probe to land in the outer solar system on a moon other than our own in the most distant Landing of any spacecraft to succeed haens would
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have to execute a perfectly controlled Landing protocol designed to use Titan's atmosphere as an arrow break before employing a parachute system to deliver the scientific instrumentation to the surface and all after Awakening itself from a 6.7 year Intergalactic sleep the probe had remained in an entirely dormant mode except for a six-monthly self- health check and only at the point of separation from Cassini was the timer set to wake the probe up 15 minutes before entering
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the atmosphere of Titan the proposed Landing site for haens also held much uncertainty chosen to be in the southern hemisphere of Titan 192.5 de West 10.3 de South to be precise the area was surveyed by cassini's cameras from an altitude of 12,000 km and appeared to be near a site that had many of the characteristics of a shoreline Landing into an extraterrestrial ocean had been part of
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haan's original design So in theory the craft was expected to survive any splash down into a liquid surface on Titan on the 14th of January 2005 the 318 kg probe entered Titan's atmosphere 1,270 km above the surface and began its descent protocol on board accelerometers monitored the Craft's deceleration waiting for the precise moment to trigger the explosive bolts that would blow off
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the front heat shield and back cover and release the pilot parachute which would then pull out the main parachute slowing the 2.7 M wide craft from its nearly 2,000 kmh descent and allowing it to drift safely to the surface all of this would need to play out perfectly while more than a billion kilometers away a group of nervous humans sat in near silence in Mission Control waiting for the first Telemetry to confirm that haens was safely on the ground every second was utterly
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critical because haggens had no more than 3 hours of battery life and with an expected 150 minute descent that meant not much more than half an hour's activity on the ground for a mission that had cost millions of dollars and taken decades to plan and execute its success would depend on this incredibly short win window of exploration despite its sophistication haens could not communicate directly in any detail with Earth instead all of its detail Telemetry would need to be relayed
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back to Earth via cassini's communication system this meant very little was known about the probe status during the 2hour and 27-minute descent but at precisely 1138 UTC the Robert C bird Greenbank telescope in West Virginia picked up the weakest of carrier signals generated by haan's 10 watt internal transmitter to confirm that haens had arrived safely on the surface this extraordinary probe was now alive and active on an alien Moon orbiting Saturn just under 5 hours later the
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cassinii probe orbiting far above the moon's surface began relaying the precious data from haens back to Earth and by 1945 that evening the first extraordinary picture was released showing A View From haens about 16 km above the fast approaching surface this was space exploration on an awesome scale a photograph taken by a tiny space probe floating down on a parachute to the surface of a moon orbiting a planet over a billion kilometers from Earth it's instantly apparent that
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this is no featureless rock the channels running across the this picture are recognizable as the geology of a world shaped by liquid covered in drainage channels crossing the landscape into what looks like a lake bed or sea and more was to rapidly follow just a few minutes later the first image from the surface arrived on Earth the first view of the surface of a world in the Frozen far
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reaches of the solar system it's an image that is worthy of the very closest of inspection because as always in science the more you know about it the more wonderful it gets what we can see in this extraordinary image is something that is exactly like a flood plane or rivered here on Earth we can say this with some certainty because you can see that the rocks are abraded they've been smoothed by the action of a liquid flowing over them but there are no rocks Higgens was able to
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confirm that these are in fact Boulders of Frozen Water Ice sculpted on the freezing temperatures of Titan surface these rocks of ice are sitting on a surface that as one haen scientist described it is like snow that has been frozen on top if you walk carefully you can walk as on a solid surface but if you step on the snow a little too hard you break in very deeply so if the temperature is so
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cold on Titan that rocks are made from water what liquid is flowing over the rocks of ice carving the riverbeds and flood planes we'd known for some time from spectroscopy carried out here on Earth that Titan had an atmosphere rich in methane gas and many scientists had wondered if this could mean that liquid methane existed on the surface but it was only when Hagens was actually on the surface and its instruments began testing the atmosphere directly that we could begin to see
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just how alien this world was for an unexpectedly long 70-minute period hens was active on the surface detecting significant amounts of methane in the air haens was also able to confirmed that the surface temperature on Titan was a freezing minus 180° C combined with an atmospheric pressure equivalent to 1.4 atmospheres here on Earth the measurements confirmed that on Titan methane was
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not a flammable gas but potentially in abundance on the surface in liquid form Titan it seemed was a wet world not with flowing water but with liquid methane driving icelike rocks Down Mountain channels and out into open flood Plains but despite early speculation haens had not made a Splash Landing it lay in a dry riverbed and after surviving for just a few hours its battery ran dead this miraculous Explorer Switched Off without directly detecting liquid methane on the surface
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it would be 2 years later as haens lay Frozen and dead on the surface of the Moon that the very much alive Cassini probe would fly high above the South Pole of Titan and beam back an image that would provide a unique view seen nowhere else in the solar system beyond Earth this was our first glimpse of liquid on the surface of an alien world a lake composed of methane ethane and propane near the South Pole of Titan named after after one of the Great Lakes of North America Ontario
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lus is like nothing we have ever seen on earth a 15,000 square kilm Lake of hydrocarbons whipped by winds that are clearly eroding the shoreline and Ontario lus was just the first today thanks to cassini's years of observation and photography we have discovered more than 40 Lakes of liquid methane including liia Mari a vast body of liquid hydrocarbons with a shoreline over 200 km in length we've seen mysterious bubbles rising from its depths kaken Mari is the largest known body
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of liquid we have so far found on the surface of Titan this hydrocarbon sea covers an area of 400,000 square kilm five times larger than Lake Superior and has a depth that we suspect descends to 160 m we've seen waves in this sea and islands and currents endlessly big being filled by the flash floods of methane rain that we are certain fall on the highlands surrounding the sea feeding the rivers and streams that flow into it Earth it seems has a strange cold twin a
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moon not a planet that is millions of miles away where Lakes are liquid methane and mountains are made from Frozen water ice as hard as rock what's also fascinating and tantalizing is that Titan has a complex chemistry a carbon chemistry the chemistry of life we have found molecules like hydrogen cyanide which are the building blocks of amino acids molecules like vinyl cyanide which chemists and biologists speculate could form some sort of cell membrane in fact all of the
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ingredients for life are present on the surface of Titan today that doesn't mean there is life in reality very few scientists think there will be life on Titan today as it is after all- 180° C at the surface but with a little heat it might be a very different story in a few billion years time as the light of the dying Sun reaches out beyond the inner solar system to touch the outer reaches with its warmth for the very first time Titan will begin to warm its mountains of ice will
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shrink and melt and the frozen water they contain will replace the liquid methane which will have evaporated away into space Mountains will become oceans and in a strange twist of fate at the end of the life of our star perhaps the Solar System's last Water World will be born David grinspoon believes it's a prediction we cannot rule out Titan today has all these juicy Organics pulled and lying on its surface and yet it's so cold and so dry that it may be that nothing is really
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happening biologically there but we can imagine a time in the far future when the sun has heated up to the point where the inner solar system has become uninhabitable where Titan may become quite habitable that methane Greenhouse will become more powerful as the sun gets hotter and at some point that icy crust will start to melt and you'll have large pools of liquid water on the surface full of
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all those complex organic chemicals and that is a recipe for the kind of place where the origin of Life can happen so even if Titan doesn't have life today and that's something we still have to search for there's every reason to imagine that at some point in the future it could be a great place for biology it's easy to think of habitability as a permanent feature of Worlds a defining characteristic if you like Earth is habitable because it's in the goldilock zone
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around the Sun not too close and not too far away but it's more complicated than that solar systems are Dynamic places over long time scales planets change orbits and their parent Stars evolve and worlds that were once Heaven can become hell we Now understand that Earth has been a fortunate World an oasis in a constantly changing solar system that's maintained a stable climate perhaps against the odds for the 4 billion years it's taken complex living things to evolve we don't
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know how many planets like Earth are out there amongst the Stars where the ingredients of solar systems have assembled into structures capable of dreaming of other worlds but we must consider the possibility that there are very few and that would make earth and US extremely rare and precious nearly a billion miles from the warmth of the sun on the outer edge of Saturn's rings lies the icy Moon of Enceladus a small Moon about the size of Iceland Enceladus is the most reflective
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object in the solar system over 90% of the light that hits it bounces back that's because the surface of this ice covered moon is covered by crevasses just like we see on the surface of glaciers here on Earth but on Enceladus these cracks in the ice occur on a much grander scale with some stretching for over 100 kilm but for all that's going on on the surface it's what we discovered beneath enceladus's shell of ice that must rank as one of the greatest surprises in
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21st century space exploration a surprise that had been hiding in plain sight for decades the first photograph of Enceladus was taken by Voyager 1 in 1980 it was actually captured unintentionally a moon photobombing the planet and nobody even noticed Enceladus until over 35 years later but when the image was eventually enhanced a remarkable feature no more than a misty blob began to emerge on one side of the moon 24 years later Cassini saw exactly the same
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thing but this time in much more detail as Cassini approached Enceladus the anomaly revealed itself giant plumes of water vapor and Ice were erupting from its surface over 200 kg of material was being released every second feeding one of Saturn's outer rings and helping to replenish it these discoveries inspired the Cassini team to take an audacious risk piloted from nearly a billion miles
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away Cassini was guided dangerously close to the plumes and using its Cosmic dust analyzer was able to actually touch the plumes of ice and collect a sample from one of the eruptions as Michelle doti scientific leader on the Cassini project explained the really close flyby that we had of Enceladus where we were 25 km above the surface is probably closer than any spacecraft has been to a
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planetary body before and the Cassini mission team said they'd never do it again because we were in the atmosphere well in the plume which was really dense they didn't lose control of the spacecraft but they felt they might because the mag boom used to stickle from the side of the spacecraft and that almost started tumbling the spacecraft what the scientists discovered though thanks to this
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and a series of similar flybys was breathtaking the plumes were spewing out of fishers known as tiger stripes being projected from deep within this ice World rising up from an ocean of salty liquid water beneath the ice how could such an ocean exist in the far Frozen reaches of the solar system the answer lies once again in the power of Saturn to control the destiny of the Moon moons in its Dominion unlike the long lost Moon of veritas that was destroyed by the
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might of Saturn to create its rings in the case of Enceladus its mother planet has breathed life not death into its structure Enceladus orbits Saturn and the planet's vast gravitational force pulls at the Moon holding it in orbit but every couple of rotations another larger Moon called dioni aligns with Enceladus drawing it back back this repeated tug of opposing tidal forces stretches
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and squeezes the moon warming its core and melting its icy interior exactly the same gravitational forces that destroyed one of Saturn's moons are now breathing life into another but it's what Cassini found in the chemical makeup of the plumes that changed everything because as it analyzed The Columns of water it discovered complex organic compounds and silica particles direct evidence
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that deep below the ice at the bottom of a salty ocean of water there were hot hydrothermal vents exactly like the ones from which we believe life emerged on earth almost 4 billion years ago out in the Frozen outer reaches of the solar system Cassini has given us a glimpse of the world beneath the ice on Enceladus and revealed a warm watery Oasis a world in which it really is possible that life could exist exciting though the prospect of life in space is if it is out there
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on Enceladus it's likely only to be home to the simplest and most primitive organisms and given how violent and changeable Saturn's past has been this world may have Arisen relatively recently we don't know how long Enceladus has been active but if it's only tens or even hundreds of millions of years that might not have been enough time for life to get going and despite all the Cav the very fact that the saturnian system holds the potential to host life is a truly remarkable
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Discovery and one that compels us to explore even more but for Cassini the Brave New World under the ice of Enceladus was a Bittersweet Discovery 13 years after it arrived in orbit around Saturn as cassini's fuel finally began to run dry the team at Nasa realized it couldn't risk letting this probe crash land on it Enceladus and contaminate a potential habitat for life as Carl Murray explains because we now knew Enceladus was a potentially habitable environment we couldn't
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risk Cassini crashing into it or coming near it because there might be microbes hitchhiking on the spacecraft and we couldn't allow contamination of Enceladus so we consciously picked an end of mission that would use up its Fuel and then send the spacecraft into the giant planet itself
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we journeyed out across space to Saturn to see this great Beauty up close but in the end we were rewarded with insights that hit far closer to home as is so often the case in Exploration and science the real treasure was found in the unexpected Shadows on this Mission it was in the shadow of the Rings because there we found a tiny world with the potential to Harbor life to provide reassurance that for the first time we might not be alone would
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such a discovery matter yes it would at this moment in history we are I think in need of reassurance or perhaps a reminder that there is great Beauty and knowledge and perhaps even life and meaning beyond our Shores we will I'm sure go back to Saturn and its moons explore deeper stay longer and maybe one day even visit there ourselves we don't yet know what we will discover but we can be sure it's a story that has only just begun cassini's discoveries
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have profoundly changed our understanding of the Saturn system from the planet itself to detailed structure in the Rings we now know what the surface of Titan looks like and we have also pierced through that Haze with the raadar to map it all out the lakes and seas are liquid methane on the surface of this Moon and then of course the big discovery of gyers coming out of the South Pole of Enceladus flying through those Geyers sampling tasting measuring
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what's coming out the gases and the particles and finding not only do you have a lot of water from that liquid water ocean but you have Organics you have nitrogen you have methane also so you have sort of the key ingredients carbon hydrogen oxygen nitrogen the building blocks for life it's so intriguing to find a moon that's only 500 km across with a liquid water ocean just one of a suite of ocean worlds in our solar system and perhaps life is just next door
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