Us for michaels last stop. Please. If we just take the time to observe it nature provides us with a fascinating spectacle. Over time the inhabitants of our planet of woven complex relationships of collaboration symbiosis dependence and predation. Earth the planet of life running crawling for flying life abounds everywhere. But for this beautiful diversity to have proliferated earth has had to provide a favorable environment for around 4000000000 years. More than with the conditions which enables the blooming of life on earth. And could these conditions be present elsewhere resulting in alternative ecosystems. In an attempt to answer these questions scientists get all the cosmos for signs of life. They built giant telescopes with which to probe the universe and listen to the whispering of the stars but space has remained resolutely silent. Scientists have sent probes to the very edges of our solar system. But all they have sent back has been images of planets inimical to life. Over the last 25 years however astronomers have discovered thousands of incredibly diverse planets in our galaxy alone. So many strange worlds with no sign of life not one of a planet similar to our own so could it be that earth really easy to make. In this Program Scientists will tell the fascinating story of how earth developed how this bowl of ice and dust became the planet of life. In their liberal and trees all around on the ground they continue their research into the extraordinary circumstances which allowed life to appear and eventually transform this planet. They said local columns although we were trying to understand with all the possible outcomes what it was that made the uniqueness of our system or system now chris it seems like earths climate fix that self to always be favorable to life thats amazing sickish are those who dont know. Each will explain the incredible saga from the viewpoint of their own discipline from the birth of our planet to todays ecosystems its a story punctuated by an incredible succession of lucky accidents of all if you like that usually theres the analogy with the lottery they get. You know if the probability of winning is that i need to win the game of planetary formation forming a solar system with our earth is like winning the lottery. Scientists are only now 15 together all the various chapters of these turbulent history our history that of a succession of helpful not just lucky chances and beneficial cataclysms. Without a helping hand from jupiter and saturn and without the moon without hurtling comments without the power of volcanoes without the genius of certain microorganisms we would not be here if its possible that life is a one off if were successful you know or else that only our last has all the conditions necessary for life as we know it theyre going to quit the. Next day also sausage in that sense earth is probably unique although we may detect some life elsewhere that it will necessarily be completely different. Only it was this mind blowing series of improbable events that made the earth the possibly unique life bearing planet it now is. The idea that earth may indeed be meek could have been spawned by these famous photo taken on the apollo 8 mission in 1968. Changed our way of looking at earth there is al planet floating like an oasis in the magnificent emptiness of space. For the 1st time there we all were bacteria mammals insects and plants on the same photo our planet a unique ecosystem and even today this photo. Of a world with clouds and envelop in its. The an atmosphere could be a learn in the universe. The 1st reason earth was able to become this welcoming blues fear is because its at just the right distance from the sun in a narrow zone not too harsh and not too cold where the temperatures are compatible with liquid water and life. But planetology just have discovered that earths a very presence in this goldilocks zone is itself to to an amazing stroke of luck. When the solar system was still young the sun came close to being taken over by the planet jupiter so how was earth able to form here. Research into the onset of this puzzle has been carried out at nice observatory. Alessandro movie delhi has written a new account of the birth of our solar system. How many is a lot is it is the climate working on the origin of planetary systems as like being attacked if you arrive at the crime scene and use the clothes to try to work out what happens if a sea. Knew about the abuses them so that act will issue from our solar system as it is we try to reconstruct how it formed and develop doc when we come up with a scenario we get a shiver of excitement with thinking that maybe weve got close to what actually happened to us here or. Planetology just start from the present position of the planets attempting to hypothesize a scenario of the Solar Systems formation with the help of computer simulations. Our solar system like all planetary systems formed from a cloud of gas and dust that surrounded the young son 4500000000 years ago. But now solicits dim seems to have a very different structure from the majority of planetary systems discovered over the last few years. Is all agree we now think that our solar system is pretty magic with them so they have a lot of chance events had to happen to fred to be as it is usually this suggests that our solar system isnt a typical planetary system but a relatively rare one more. Because shamash when we look at planets around other stars we see that when its of a similar master jupiter are found an earth spark class then i feel this is important if jupiter was in this part of earth it wouldnt be here so they pull up. The discovery outside our solar system of giant planets similar to jupiter but much closer to this star posed a serious puzzle for astronomers because giant planets of that kind cannot form in such zones really planets are far with lana to form in a disk of gas and dust that surrounds the young star the giant planets form far out where its cold where theres ice which lets these planets grow to a huge size close. Like a snowball rolling down a snowy heal the planet grows ever. Or bigger as it gathers to itself all the dust in its path. It calling it collect when a planet gets big enough when it acquires enough mass it migrates inwards towards the star was on the. Understanding this phenomenon was a real revolution planetary migration explains why the majority of giant planets discovered elsewhere in the galaxy dont stay in their distant orbits as they formed a spiral inwards towards this stone but in that case why didnt our own giant jupiter migrate closer to the sun why did it stop just in time leaving the space free for the future earth. Young scepter should on football saturn is very important this is a giant planet too and as weve studied the dynamic between jupiter and saturn weve realized that saturn was able to stop jupiters migration and even reverse that conviction so jupiter started migrating to the sun but when saturn appeared there was a complicated gravitational effect which reversed the migration and the planets moved further from the sun one usually. Thanks to saturn the giant planet jupiter changed trajectory it left the in a zone of the solar system and it was this change of course that saved earths future. Without the intervention of saturn and jupiter would have ended up in the zone where earth now is earth would never have formed. Our planet was luckier than its future neighbor. Because on its migration jupiter passed through design when mars was forming. The giant planets swallowed up a lot of the material available leaving only crumbs for months and now neighbor would end up with 110th the mass of earth which in turn reduced its possibility of maintaining an atmosphere favorable to life. Could i make us were understanding how planetary migration totally changes how the planets get distributed player size their position in space and the collisions between these objects before they stabilize the planets make the system developed and its only particular way with a 50 year. Narrowly saved by assassin our planet could keep on growing and being just the right distance from the sun meant that it would later have liquid water on its surface. And yes 4500000000 years ago our planet was completely dry it formed in the rockies own of the solar system gathering up dust with barely any water content so where did this water which would later give us our oceans come from. After initially in danger ing our young earth jupiter would give it a helping hand. For most young to be deadlocked cos we think that the formation of the growth and the migration of jupiter let these bodies which formed far out in the Solar Systems and so there was cold bodies with water they sent towards the enters i dont know where they crashed into the still forming earth contributing their elements to it up or down or zillion more that they. These bodies asteroids and comets enrich the chaotic pull of mass which both thin walls with water but as our planet started to solidify the water molecules remain trapped under the surface in the magma. Yes an essential mechanism for our planets future was already in place and starting to bring some of that truck to the surface. Its a mechanism thats still very active today. With. These folks hey knows these mountains of fire has been helping to bring water to the surface from the very beginning in earths youth there was a lot more full kind of activity than today. So michael i mean how both when you 1st think about it you think of lava danger and life threatening option but volcanoes are essential for life as we view it that can occur in the. Sailor destruction on duty does the struction a San Juan Village by them ok no particular team in 1940 on too bad the people had to move away it was a real catastrophe so to know the artist has made the volcano quite small to get the whole region was devastated. Yes it appears from nowhere in a cornfield was i thought no one could have expected it when the village was destroyed that it was still quite small but take all. You would call some balck a nose arent inimical to life on the contrary they were necessary for life to develop throughout earths existence to do cool things things about them. But also are such explosions common. They happen but just not that office ive been here 6 years and ive seen 4 or 5 with an explosion like that of ash may fall on surrounding villages forest and you guessed it so whats the gas made of to complete it. Ill say its 95 percent water vapor in all ok no the around the world its mostly water was on a preserve all along. The water vapor spat out by the volcanoes allowed the water trapped in the earths ballast to make its way to the surface. This has always been an essential mechanism for keeping our planet hydrated and alive. Point 4000000000 years ago thanks to the volcanoes earth sky changed filling with clouds. Dilute the and rain started to lash the surface ukraine for millions of years and the 1st oceans formed. Yet barely had they appeared than they could have just as quickly evaporated. As to finish seems the difficult bit is having liquid water you dont just need age to well you need enough atmospheric pressure at most an atmosphere on the moon theres no atmosphere so theres never a better you look at what you want to. Give birth cert must be a hadnt been dense enough the water would have evaporated into space in the form of vapor. Fortunately the gas produced in abundance by the volcano has maintained enough of an atmospheric pressure for earth to be able to hold on to its early oceans. But the oceans of the young earth soon faced another danger that the freezing over. The sun was still weak 30 percent less bright than it is now earth therefore needed a greenhouse effect to keep its surface warm enough and its water in a liquid state. This greenhouse effect appeared very early on in earths history thanks to the water vapor and c o 2. Abundantly present in the atmosphere. Will be in the city today of course we know that c o 2 increased by human activity is a bad thing too much as a good but we needed some back then and still do if there wasnt a bit in the atmosphere the surface temperature would be 15 degrees colder can in fact then with the sun younger and less bright it would have been much colder cougar earth would have been frozen but about minus 60 degrees thats also not favorable to life he said of. The volcanoes where yet again contributing to making earth habitable in their ex aleisha as they were constantly spewing out huge quantities of c o 2 along with the water vapor. The c o 2 sat out by the volcanoes accumulated the greenhouse effect increased the ice melted and the oceans thought it could be we think this happened 400 to 500000000 years ago we call this period snowball earth and earth emerged from it like that if its the greenhouse effect increased and we got back a climate with liquid water favorable to like. Be celibate. But with the constant eruptions the c o 2 from the volcanoes was steadily accumulating in the young earths atmosphere the greenhouse effect could have gone out of control turning out planet into a furnace. Fortunately that was a safety valve c o 2 can dissolve in water. Over millions of years and its trapped in calc areas formations and no longer acts as a Greenhouse Gas he remains trapped you know at the bottom of the ocean in mineral form. The quantity of c o 2 in the atmosphere then very stupid being on the amount of liquid. Water on the surface. Of a very long time scales this make an ism regulates our planets climate. Fascinating thing about or which may make it unique is that all through its very long existence all 4 and a half 1000000000 years variations in the luminosity of the sun have been compensated for by a variable greenhouse effect. And if its. Like a sort of geographical thermostat keeping the earth always in a habitable with oceans on the surface want to show us. That these thermostat needed one more tweak to get it working perfectly and make our planet truly favorable to life. Over hundreds of millions of years the c o 2 in the atmosphere could have ended up trapped in the form of count carious wrong at the bottom of the ocean. It wouldnt have been enough in circulation to keep the thermostat going and it would have broken down. A mechanism possibly unique to our planet allowed for the reinjection of c o 2 into the atmosphere plate tectonics. That their life was compunction you have to realize that the earth has a sort of crust of cold and solid rock inside theres a warmer rock the mantle which changes shape and all this is. A clue so you might imagine that the crust forms a solid complete shell like an egg shell around a softer inside but thats not right the movements of the shifting rock on the inside were powerful. Enough to rub up against of the crust and a crack in the places that. The earths crust is fragmented into 10 plates which are displaced by the movements of the mantle. Where the plates come together they crunch over each other dragging the rocks that were at the bottom of the ocean deep into the bowels of the earth and also just the c o 2 recycling begin. Under the enormous pressure and heat the ropes melts and the magma is spewed back out onto the surface taking the c o 2 with it. The c o 2 escape seen gas form during volcanic eruptions finally back in the atmosphere the c o 2 may or may not be captured again by the oceans depending on climatic conditions the circle is complete. Sent on most issues its a very particular geophysical thermostat which we think has really controlled the climate conditions on earth and made a life impossible namely that just. To see if you changed in the plate tectonics just a little having slightly more or fewer than 10 plates and then with the recycling in c o 2 concentration would have been different and the bias heres what evolved differently or to. See. If there yes so and this begs another important question of gold sick this at plate tectonics just which seems to be the key the key to life on earth there is in light tectonics something really common in the rest of the galaxy angels and or something unique more very. Prayerfully ha and thats all our system you dont find anywhere else in the back and i knew by your. Plate tectonics may be the factor which earths neighboring planets lacked for life to appear and survive then. Yet one of the Solar Systems on the rocky planets did get off to a good start early in its history with volcanoes c o 2 and mars enjoyed an environment similar to earths. I dont know if you so there was an environmentally im not imagine a blue mars with lakes and rivers up on something there was an ocean in the Northern Hemisphere it also it was an environment of favorable to life of peace and i think. All would seem to have been set up then for the planet to function in a similar fashion the current state of the red planet however clearly shows that something went wrong. So mass and young mars cooled down much faster and i disagree massive plans mars is half the size of earth and its a bit like comparing a huge pot of hot water to a cup of d. C. I mean bushels of a big part cools lower than a cup of tea which is mars i dont die and that the inside call it faster is south but they are so there was no chance as we understand it for plate tectonics to arise by you so if there was no recycling that could maintain a climate favorable to oceans for billions of years mars had hundreds of millions of years and there is something in there after at least came a very sterile planet and it pristine. Mars is tragedy is that its too small and fell into a deadly spiral because of its smaller mass there was insufficient gravity to hold on to its atmosphere and the drop in atmospheric pressure was the next or. And the solar wind swept it all away some of the water evaporated the rest froze blue monster became red mas a victim of its own small size. And i was about all out there so you think the earth is just the right size so why is there no flame tectonics on venus which is the same size as earth with us why is that time one of the unlike earth has been is has hardly any water the waters all gone and the mantle is very dry not very lubricated if you cant move much more doesnt place any plates on the surface especially new so venus has a sort of unbroken shell all around the planet it doesnt have the mechanism that earths atmosphere so its not just important to be the right size but to have water in the mantle of the devil they really dont want to. Birth has enough water to lubricate its plate tectonics venus doesnt and yet the 2 planets were formed from the same materials. One very special event during earths youth could have hydrated its depths. This is us you know this is the idea for the mantle to have got sufficiently hydrated sufficiently lubricated early in its existence earth suffered a huge cataclysmic hes in we think that the young earth was struck by another planet the size of mars which we call taya. A few tens of millions of years after its good earth suffered a cataclysm which almost destroyed just how bright the chaos of the Solar Systems origins. Still reigned. Measure you know imagine a round earth hundreds of moons or dozens of the planet mars colliding repeatedly these objects grow in the form planet maybe planets. If you suddenly an object the size of mars comes towards our ea