How did water get on earth Where does water come from


Arvin Ash


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it's the reason we are here it's the one substance without which no life on earth could exist we couldn't survive more than three days without it I'm talking about the most valuable substance in the university to mankind h2o or water water is everywhere on Earth in all its forms gas liquid and solid and this is what makes Earth unique in our solar system water is found on many other planets and moons but not in all three forms the earth has an estimated 325 million trillion gallons of it but here's the mystery earth began as a barren lifeless waterless ball of fire in the sky there could not have been much water to start so where did all this water come from join me as we go on a remarkable journey of one molecule of water from the time of creation to today coming up right now a single molecule of water is made up of just three atoms two atoms of hydrogen the most abundant substance in the universe and one atom of oxygen much rarer than hydrogen but still abundant the journey of the first molecule of water starts almost at the beginning of time 13.8 billion years ago at about the time of the Big Bang there were no atoms formed yet only protons and neutrons it took about four hundred thousand years for the universe to cool down enough for electrons to be captured in orbits around protons and this is what formed the first atom it was hydrogen hydrogen is made up of just one proton with a positive charge that has captured one electron with a negative charge one electron spinning around in a fuzzy cloud of probability around one proton so this is how the first two atoms of our three atom structure of water came about the oxygen portion of water had a much longer journey oxygen is a much heavier and more complicated atom than hydrogen it has eight electrons orbiting a nucleus consisting of eight protons and eight neutrons it took about another six hundred million years or so before the first oxygen atom to form because it required nuclear fuel this is literally when smaller atomic nuclei like hydrogen and helium fuse together to form a heavy nucleus like that of oxygen this kind of nuclear fusion can only occur in nature in one place and that's in the heart or Center of stars the earliest stars were massive much more massive than our Sun but this also made them short-lived perhaps only a few hundred million years compared to the lifetime of our Sun which is estimated to be more than eight billion years and about 600 million years after the Big Bang is when some of the first stars began to go supernova but just before these massive supernova explosions in their core lighter atoms fuse to form heavier atoms like oxygen carbon and others when these stars blew up in huge supernova explosions in oxygen and other heavier elements began to disperse into space and spread out helped by the force of the explosion and solar winds when this spewed option mixed or commingled with hydrogen and an energy source of some kind perhaps heat from a nearby stellar explosion or lightning yes there can be lightning in space hydrogen and oxygen with the help of some energy fused together to form water after formation of this water it eventually turned to ice in the coldness of space and mixed with other dust particles that were simply floating in space for eons of time and when enough dust from multiple supernova explosions collected over time in one spot the gravitational pull of all this matter began to coalesce and collapse into another generation of stars the leftover dust from the star formation coalesced into planets planetesimals asteroids and comets so you would think that since water coalesced into planets our planet would have all the water it has today from it's very beginning but it turns out that the most recent evidence shows that this was probably not the case because Earth had huge cosmic impacts one of these was a colossal impact with an other early planet the size of Mars called Theia they are collided with earth and essentially turned it into one giant piece of molten rock the debris from this collision is what eventually created our more the heat and violence of this collision would have evaporated most of the water on earth while some would probably remain due to gravity a lot of water would have spewed back out into space so most scientists believe that the massive amount of water we see on earth today must have come from another source long after the earth was formed up until recently most scientists thought that the most likely water delivery candidates for comets you might be familiar with comet's comets like the 1995 L Bob or the 1986 Halley's are full of water they're best described as dirty snowballs in fact water is what causes the huge tail of the Comets then you can observe even from Earth the frozen water on these comets evaporates as it gets closer to the Sun but in 2012 researchers found that the chemical makeup of water on comets doesn't fit with the chemical makeup of water on earth what chemical makeup did they measure they measured the ratio of hydrogen isotopes called deuterium and protium it turns out that all water consists not only of podium the normal form of hydrogen but also a tiny amount of dutrey this is also called heavy water because the nucleus contains a neutron in addition to a proton making it heavier the deuterium to protein ratio measured on four comets including Halley's and hail Bob was about double the ratio found on ocean so this means that the water that's present on comets since it doesn't have the same makeup probably did not deliver water to earth so how then was the water delivered to earth well it turns out that the source was from objects much closer to Earth than comets which live extremely far away in a formation called the Oort cloud the source of Earth's water is most likely your everyday humble asteroid you know like the one that killed the dinosaurs 65 million years ago it turns out that early asteroids had huge amounts of water too since they had not been exposed to the heat of the Sun for as long as they have now the isotope ratios of near-earth asteroids wouldn't you know it matches almost perfectly with the isotope ratios of water that we find on earth so it turns out that the dinosaur killing asteroid was not the only one that hit the earth many such asteroids probably hundreds or thousands of them hit the earth early in its history this period even has a name it's called the late heavy bombardment period of Earth and it happened about 3.8 billion years ago about 600 million years after Earth's formation and these asteroids will form from the same dust ice and other substances as the early Earth and all those substances probably came from multiple supernova explosions spewed out into space over billions of years since the beginning of the universe so the next time you drink a glass of water think about the journey that every single molecule of that water is taken from the center of stars to floating along dust clouds for billions of years in space to the formation of asteroids to its collision on earth to the formation of oceans to evaporation to clouds to rain into rivers and to your bottled water that goes in your body if that molecule could talk they would tell you one amazing story Arvind osh here if you like our videos and consider subscribing and ring the bell so that you can be informed when we upload more in videos we make one or two videos a week we'll see you in the next video [Music] you