danger and life threatening eruptions but volcanoes were essential for life as we know of you know if that can occur in the. same district on tuesday does the destruction of san juan village by them ok no particular team in 1940 don't do better the people had to move away it was

a real catastrophe hits and the artist has made the volcano quite small to get the whole region was devastated. yes it appears from nowhere in a cornfield was at all no one could have expected it when the village was destroyed but it was still quite small but take all. you would call some balk a nose aren't inimical to life on the contrary they were necessary for life to develop throughout earth's existence to college don't forget them.

what else are such explosions common in they happen but not that office you know i've been here 6 years and i've seen 4 or 5 with an explosion like that ash may fall on surrounding villages forest and you guessed it so what's the gas made of a composite i'll say it's 95 percent water vapor in all ok no the around the world it's mostly water on the preserve all along. the water vapor spat out by the volcanoes allowed 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 played rated and a life. full 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 full and. yet barely had they appeared then they could have just as quickly evaporated. skittish seems the difficult bit is having liquid water similarly you don't just need age 2 well you need enough atmospheric pressure an atmosphere i mean on the moon there's no atmosphere so there's never better you look 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 of 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. was already 2 months 6 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 do come on that there wasn't a bit in the atmosphere the surface temperature would be 15 degrees colder if you had back then with the sun younger and less bright it would have been much colder beaucoup earth would have been frozen but about minus 60 degrees it's also not favorable to life be said of. the volcanoes were 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 they. pursued 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 or 500000000 years ago we call this period snowball earth and the earth emerged from it like that if it's the greenhouse effect increased and we got back a climate with liquid water favorable to likely key to be celibate. 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. and 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. that's fascinating thing about earth which may make it unique is that all through it's 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. and if it feels. like a sort of geographical thermostat keeping the earth always inhabitable with oceans on the surface is also want to show us.

but 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 carious roll 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 and c o 2 into the atmosphere plate tectonics. that their life is a component you have to realize that the earth has a sort of cry. last of cold and solid rock really auspicious inside there's warmer

rock the mantle which changes shape and all this is soft a clue so you might imagine that the crust forms a solid complete shelled like an egg shell around us softer and softer but that's not right the movements of the shifting rock on the inside were powerful enough to rub up against the crust and crack it in the places that. 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 dulce 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 seeing 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 possible even. if you changed in the plate tectonics just a little having slightly more or fewer than 10 days later and then with the recycling in c o 2 concentration would have been different and the bias of yours would have evolved differently or. see.

in there yes so pencil bags another important question a little secure this a plate tectonics just what seems to be the key the key to life on earth in the history of there so it's been laid tectonic something really common in the rest of the galaxy and also the more something unique and more very rare. and that's all our system you don't find anywhere else in the black you know new bio. plate tectonics maybe the fact to which earth's neighboring planets lacked for life to appear on 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 here so there was an environment imagine a blue mars with lakes and rivers up on something there was an ocean in the northern hemisphere and also it was an environment of favorable to life of peace

and i think. well 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 that i disagree massive designs 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 cooled slower than a cup of tea which is mars i would die and that the inside cooled faster is south but they 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 mars had hundreds of millions of years and there is something there after at the came over. very sterile planet

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

earth so it's not just important to be the right size but to have water in the mantle and that a bit of elderly don't want to. earth 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 a. mars which we call 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. if. you measure you know imagine you're around earth hundreds of moons or dozens of the planet mars colliding repeatedly these objects grow in the form plan 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 climate possible. thing it crashed into the energy released by these enormous collision was acquittal into hundreds of billions of hydrogen bombs. back to the impact is so violent that

the impacting object is destroyed less fuel for the surface of the earth is completely liquefied 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. though. the collision was so violent that the water contained in was driven deep into with school mixing with the water already present there in this way they are hydrated the depths of the earth's mantle making it possible later for the plate tectonic system to function. as a species me she said speculative 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 the 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 move. this system to the earth moon system is unique in the solar system and as far as we know in the galaxy 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 had to go. barely

had it coming to 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. in his shop little in the apollo missions placed reflectors on the moon surface now these are factors are used today to reflect back laser beam as emitted from earth such as this one behind me and i while. there's a regular emission from here the callahan plateau in the frat house scene would have phones. today many observatories around the world like this one in the outdoor program. moment to the moon closely every night scientists use

a laser beam to make a precise measurement of its distance from earth. as experiments will close up on these are important experiments because we can measure how long it takes the laser beam to go to the moon and back it so we can measure in real time the distance to the moon. 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. for most when 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 said it was going to acknowledge it's 380000 kilometers from earth but 4000000000 years ago we

think it was only 15000 kilometers distant cousin to the med that out there. that post you need to let rock so many of the moon had a 1st consequence of creating bigger types and therefore maybe stimulating biological evolution to. '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 earth's rotational axis. at the face of a something modern that the effect wasn't just the tide it was much more that it stabilized to the famous tilt on the angle of 23 degrees if i was worth a look at this is a built in relation to its trajectory around the sun will you say and this angle has stayed constant for billions of years then they see you knew no door that if the moon hadn't been there the earth rotates. small access would have oscillated

causing rapid changes in the climate this could have had huge consequences on evolution that with rapidly alternating areas of glaciation and warming for example along the belt of let's assume that although i shot for. the moon helps the earth maintain a climate stable enough for the slow and gradual evolution of life. was. without the moon the earth would have been faced with the same up evils as its neighbor months. sure the mounds of mars phobos and deimos are so small that they play no

stabilizing role on the rotational axis. if there have been a very big variations in the rotational axis of mars afs. what's more that's rotational axis has moved all around the surface of mars so badly as a fuzzy office. mons became a desert earth a garden of eden. live 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 and surely everything was perfectly set up. life to appear and evolve but the earth still lacks the basic ingredients

of life organic molecules. all living things on earth are 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. limerick you are all gaining the organic molecules of the basic elements necessary for life these are found in space only to hold on to your destiny only hold their media rights some are 60 percent organic material which is you know and a lot still to earth. the original organic molecules which may have sown in 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 rosetta mission the 1st to ever attempt

landing a module on a comet shed some light on this mystery. jumpier be bring was one of the scientists behind this all day she's mission ses go on that was here to this is what we saw on the 14th of july 4014 when we got there we thought oh i suppose we can't land on that it's not feasible without it this is tiny it could you know nothing of the whole thing is only 4 kilometers and it's revolving around an outward act like that 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 you have killed a few days here you see the 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 i'm on 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 yet but new to adore us of there is no water on this comet surface no there isn't an ounce of ice without it most of the ice with a few molecules not at all always 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 libertarian alice's of organic molecules similar to those which fell into earth's oceans this was the end of the high of booze a 2 mission launched by the japanese space agency to bring back to earth the few fragments of this original organic matter. the sample was collected in july 29 teams 300000000 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 there you know i thought it's mind blowing out of what i hope and then you see it take off again capacity to create the principle for taking examples as for it not to linger in this song it touches down over the fires a 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 at their heels you. are saying i think it's completely mind blowing we hope that in a sample of this carbonaceous material from which we think 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. up to listen to tell you a lot 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 vision ok 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. back.

everything online. the labor market completely digital at this startup even much comes out of the printer. what about working from home an email here a child message they're the ones who call away from burnout your psychological hygiene or you'll get a remote telling off from the doctor maybe he needs the most screen time is out of the question we have to turn back we're also it's really going to be game over made in germany. to 30 minutes on w.

. into the conflict zone with tim sebastian faulks for years now the government of bangladesh is being criticized around the world for its human rights record my guest this week from back eyes galleries meet foreign affairs advisors of the country's prime minister well real hard to stop denying the truth about the repression babe inflicted and clean up their act conflicts of. 90 minutes on the. german. and jewish. i'm jewish so also. does that mean in daily life. and at school isn't something we shouldn't be given a special status but be completely no one. they don't know what's wrong as for the

bugging about it is images of 11 teenagers 11 stories are. safe i'm jewish and so. young german and jewish starts feb 22nd on d w. this is g w news and these are our top stories germany's federal and state leaders have agreed to extend the country's current coronavirus walked out until march 7th of schools and hairdressers will be allowed to open sooner in some places the decision came after chancellor angela merkel held a virtual summit with the leaders of germany 16 federal states schools shops and bars restaurants and leisure facilities have been closed in germany since made it just.