danger and life threatening eruption but volcanoes were essential for life as we know of you at that point when he. said destruction on you does this is trucks in a san juan village by the volcano particle teena 944 you don't want to bet the

people had to move away it was a real catastrophe said 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 that all no one could have expected when the village was destroyed that it was still quite small but take all. you would call some fall came those aren't inimical to life on the contrary they were necessary for life to develop throughout earth's existence to stones at them.

but offs are such explosions common. they happen not that often i've been here 6 years and i've seen 4 flies with an explosion like that of ash may fall on surrounding villages forest and you guessed it so what's the gas made of a composite i don't say it's 95 percent water vapor in all ok nose around the world it's mostly water on a preserve all along. the water vapor spat and by the volcanoes allow the water trapped in the earth's balance to make its way to the surface. this has always been an essential mechanism for keeping our planet hydrated and of life. cool point 4000000000 years ago thanks to the volcanoes earth sky changed filling with clouds. dilute the and rain started to lash the surface big rain for millions

of years and the 1st oceans formed. yet barely had they appeared then they could have just as quickly evaporated. skittish seems the difficult bit is having liquid water so long and you don't just need age too well you need enough atmospheric pressure an atmosphere i demand on the moon there's no atmosphere so there's never better you look at what you want to do. if the earth's atmosphere hadn't been dense enough the water would have evaporated into space in the form of vapor. fortunately the gas produced in abundance by the volcanoes 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 woman off and its water in a liquid state. this greenhouse effect appeared very early on in earth's history thanks to the water vapor and c o 2 abundantly present in the atmosphere. will be 216 a day of course we know that c o 2 increased by human activity is a bad thing too much as i'm good but we needed some back then and still to come on the most faith there wasn't a bit in the atmosphere the surface temperature would be 15 degrees colder i can back 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 it's also not favorable to life appleby said of. the volcanoes where yes again contributing to making earth habitable in their x. aleisha ins 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 we think this happened 400 to 500000000 years ago we call this period snowball earth and the earth emerged from it like that if it's in the greenhouse effect increased and we got back a climate with liquid water favorable to like a kid. but with the constant eruptions the c o 2 from the volcanoes was steadily accumulating in the young earth's 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. dissolves in water. over millions of years and it's trapped in calc areas

formations and no longer acts as a greenhouse gas he remains trapped you know that at the bottom of the ocean in mineral form. the quantity of c o 2 in the atmosphere then varies depending on the amount of liquid water on earth's surface. over a very long time scales this make an ism regulates our planet's 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 luminati of the sun have been compensated for by a variable greenhouse. and if it's. like a sort of geographical thermostat heating the earth always inhabitable with oceans on the surface is also 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 but the c o 2 in the atmosphere could have ended up trapped in the form of count carey is wrong at the bottom of the ocean. they wouldn't 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 is complete you have to realize that the earth has a sort of cry. of cold and solid rock the oscar show inside there's warmer rock the

mantle which changes shape and all this is softening a clue so you might imagine that the crust forms a solid complete shelled like an egg shell around us alter and socks if i see but that's 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 where. the earth's 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 dance just the c o 2 recycling begin. under the enormous pressure and heat the growths melt 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. sometime with the show it's a very particular geophysical thermostat which we think has really controlled the climate conditions on earth and made a life impossible. 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 here's what evolved differently they or. just see.

if they yes not so petty little bags another important question a little sick of this a plate tectonics just what seems to be the key the key to life on earth he left his yacht there so it's been late tectonics or something really common in the rest of the galaxy it was in the or something unique were very rare. in a solar system you don't find anywhere else in the black and i knew by you. plate tectonics maybe the fact to which earth's 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. enjoyed an environment similar to earth's. i don't know if you so there was an environment 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 obese and i

think. well would seem to have been sent out 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 that i disagree massive events mars is half the size of earth and it's a bit like comparing a huge pot of hot water to a cup of easy i mean a big pot cools slower than a cup of tea which is mars i don't die and that the inside cooled faster is south but there also 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 to me on mars had hundreds of millions of years because something there after it became a very. sterile planet and it pristine.

monsters tragedy is that it's too small and fell into a deadly spiral because of its smaller mass there was insufficient gravity to hold on to it's not miss fear the drop in atmospheric pressure was inexorable and the solar wind swept it all away and some of the water evaporated the rest froze blue months became red mass a victim of its own small size. and only about all of this so you think the earth is just on the right size so why is there no plate tectonics on venus which is the same size as earth cost us why is that time one of the unlike earth has been is has hardly any water the water is all gone and the mantle is very dry not very lubricated if you can't move much or doesn't place any plates on the surface especially when you're so venus has a sort of unbroken shell all around the planet it doesn't have the mechanism that

earth's atmosphere so it's not just important to be the right size but to have water in the mantle and we have all the. birth has enough water to lubricate its plate tectonics venus doesn't and yet the 2 planets were formed from the same materials. one very special event during earth's youth could have hydrated its depths. this is us you know this is the idea to it for the mantle to have got sufficiently hydrated sufficiently lubricated early in its existence earth suffered a huge cataclysmic in we think that the young earth was struck by another planet the size of my. ours which we call taya the young.

a few tens of millions of years after its birth that suffered a cataclysm which almost destroyed just how bright the chaos of the solar system's origins still reigned. we made you know imagine a round earth hundreds of moons or dozens of the planet mars colliding repeatedly these objects grow in the form planet i mean the planets. if you suddenly an object the size of mars comes towards our earth and crashes into the surface at a speed of something like 15 kilometers per 2nd act and then the possible. thing you know crashed into or the energy released by this enormous collision was equivalent to hundreds of billions of hydrogen bombs. back to the impact is so

violent that the impacting object is destroyed less still for the surface of the earth is completely liquified and the core of the impacting body penetrates the earth's mantle and it's becoming part of the earth's core we think the earth's core fused with that of the impacting body. the collision was so violent that the water contained in the year was driven deep into with school mixing with the water already present there in this way they are hydrated the depths of earth's mantle making it possible later for the plate tectonic system to function. as a species secular to us but if it's right and it's impressive shows us that for life to have existed on earth all this time that we needed that chance impact a very early in earth's history to hydrate the mantle and maintain its lubrication and have this phenomenon. this geophysical thermostat all throughout the planet's

existence would have been at. least seeming catastrophe would end up being beneficial in another way as earth gained a new companion which would play a major role in the blossoming of our ecosystem out of the cloud of debris resulting from the collision a new body would gradually form the moon. this is them down to the earth moon system is unique in the solar system and as far as we know in the galaxy it is that it's a very particular system where both objects are large objects this is why certain astronomers talk of a double planet but i've got. barely

had it come into existence than the moon was already exerting a powerful influence over the earth because of its considerable size. the history of the earth moon relationship has been studied very closely thanks to the apollo missions. minister pulled in the apollo missions placed reflectors on the moon surface now these were factors are used today to reflect back laser beams emitted from earth such as this one behind me and i while. there's a regular emission from here at the callahan plateau in the frat house soon the phones. today many observe the trees around the world like this one in the outdoor proneness. moment to the moon closely every night scientists use

a laser beam to make a precise measurement of its distance from earth. as experiments in a close up of these are important experiments because we can measure how long it takes the laser beam to go to the moon and back. so we can measure in real time the distance to the moon's down and one major finding which we sort of knew before but are now sure of is that the moon is moving away in a way it's moving away at a speed of 3 or 4 centimeters per year ready. these measurements have shown that when it formed the moon was much closer to the earth than it is today. as we went in soon after the moon formed if anyone had been here to see the moon it would have been gigantic in the sky because it was so close to them so that's going to acknowledge it's 380000 kilometers from earth but 4000000000 years ago we think

it was only 15000 kilometers distant doesn't think you meant that. that portion a deliberate so many of the moon had a 1st consequence of creating bigger types and therefore maybe stimulating biological evolution to take. 'd the times caused by the moon churned up the oceans and contributed to the dynamism of our ecosystem and the mutual attraction between the 2 bodies also had a crucial effect on me oh it's rotational axis. this had to face about something more than what the effect wasn't just the tide it was much more to that effect that it's stabilized to the famous tilt zone the angle of $23.00 degrees if i was at the stilted in relation to its trajectory around the sun will you say and this angle has stayed constant for billions of years then it seems you know we both knew no door that if the moon hadn't been there the earth rotates. final axis would

have oscillated causing rapid changes in the climate and this could have had huge consequences on evolution that with rapidly alternating periods of glaciation and warming for example long that all the less assume that although i thought. the moon helps the earth maintain a climate stable enough for the slow and gradual evolution of life. without the moon the earth would have been faced with the same up peoples as its neighbor among us. the mounds of mars phobos and deimos are so small that they play no stabilizing

role on the rotational axis. and there have been very big variations in the rotational axis of mars afs. what's more this rotational axis has moved all around the surface of mars that's about it i suppose ops. mons became a desert earth a garden of eden. leapt out at the present earth moon system is the result of a long series of accidents making the earth and moon a unique couple in each. earth now had a stable climate and atmosphere and liquid water surely everything was perfectly set up for. life to appear and evolve but earth still learns the basic ingredients

of life organic molecules and. all living things on earth a made of the same building blocks long carbon based molecules scientists now think that a large proportion of these molecules came from outside the planet earth. limit if you look on any of the organic molecules all the basic elements necessary for life is are found in space only hold on your destiny are already there in media right some are 60 percent organic material which is you know and a lot still to earth. the original organic molecules which may have sown the seeds of life on earth were present in the distant cold zone of the solar system but how did these building blocks of life travel to our planet the runs into mission the 1st to ever attempt

landing a module on a comet shed some light on this mystery. shown here be bring was one of the scientists behind this all day shoots mission south is gone that was very good this is what we saw on the 14th of july 2014 when we got this we thought was i suppose we can't land on that it's not feasible with us if this is tiny it could you know method of the whole thing is only 4 kilometers and it's revolving around an hour after that i said we thought we'd never find a spot to stand down it was crazy so it covered more for. a few months later the probe feel a managed despite all the difficulties to touch down on the comet cheery. always here appear if you know it here you see he lies leg and an object made just a few years ago. you know and here the oldest object in the solar system the same

as when it formed 4600000000 years ago it was the 1st time and it will happen again so much more that we set something down on a comet. with the 1st analyses the scientists realized that comets are very different from what they had supposed in the up value to adore us of there is no water on this comet surface you know there isn't an ounce of ice we thought it was like the ice with a few molecules not at all all we see here is organic material for that matter are getting. thanks to the rosetta mission scientists discovered that comets are abundant in the building blocks of life. up until then they had thought that only asteroids little rocky bodies with us in doubt. since the birth of the solar system comets and asteroids

have gravitated in the colder regions where they capture and store these original organic molecules. then these comets and asteroids veritable messengers of life transport these molecules into the inner zones of the solar system. as they pass close to a planet they disseminate these building blocks on to the surface providing it with the wherewithal for life. scientists are keen to undertake laboratory analysis of organic molecules similar to those which fell into earth's oceans this was the aim of the higher who's a 2 mission launched by the japanese space agency to bring back to earth a few fragments of this original organic matter. the sample was collected in july 201-9300 1000000 kilometers from earth the mission. it

was a success there in the mall this is the moment when it touched down the hallways you know picking to see the leg touching down to a cell it's mind blowing a lot of help and then you see it take off again to proceed to collate the principal for taking samples as for it not to linger in this song it touches down all of the myers the bullet and leaves again with the debris that the guy it takes a few seconds with us and it all happens very far from earth of course that there are still. a savings it's completely mind blowing we hope that in a sample of this carbonaceous material from which we think well life on earth began appearing. in the probe is bringing back a 10th of a gram of these precious building blocks of life similar to those which landed on the planets of our solar system some 4000000000 years ago. at the euro from this material we want to find out what the initial ingredients

were in the waters of earth primordial oceans and all that made possible the great chain of terrestrial biology your version can i stop. comets and asteroids could be the missing links of a long chain the chain began with the simple molecules found in the early cloud dusts and culminated with the building blocks of life from which life on earth 1st sprang the chain leading to life. last.

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