Where does all the water come from

[dubmarine]

the universe is full of water but where is it made and how ?

 

[russ_watters]

The universe is full of hydrogen, not water. And it is there because it is the simplest atom and was formed, I think, from energy condensing from the Big Bang. (someone else clarify that last part...)

 

[dubmarine]

ok cool but that still doesn't help me to know where all this water is coming from , is the water being made on Earth and if not where and how ?

 

[LURCH]

I'm told b my science prof that the water on Earth came mostly from commets. He said the Earth started out with nothing but hydrogen and hellium for an atmosphere, because that's what enarly all the universe is made of. That atmo got blown away when the sun ignited, and was replaced by the atmo we have today. This current atmo was formed by CO₂ and Nitrogen from volcanism and water from commets. He expalined that the commets were made in the early formation of the Solar System, and were afr enough from the Sun to evade incineration when it ignited. But he never did explain how they formed out of water when everything else was jst Hydrogen and Helium.

 

[dubmarine]

thanks Lurch, i have heard that our water comes from comets but was not sure , of course this leads to the obvious question where do comets get there water from ? hydrogen is plentifull but what about oxygen and where and how are they put together to form water ?

 

[Hootenanny]

thanks Lurch, i have heard that our water comes from comets but was not sure , of course this leads to the obvious question where do comets get there water from ? hydrogen is plentifull but what about oxygen and where and how are they put together to form water ?

Water can be formed when hydrogen in combusted in air / oxygen.

 

[vanesch]

Exactly because of this issue, one is convinced that our solar system is a "second generation" solar system, in that the material that made up its forming gaz cloud was at least mixed with material from former supernovas. In supernovas, heavier elements than Helium and a few other light elements are produced (I'm not really an expert, but I think it is in fact the only mechanism to get the heavier elements). So all iron, oxygen and all that which is around, came from a former supernova explosion.

In a first generation solar system, these elements are not present.

EDIT: uh, the above is not correct! It is only for elements heavier than iron that this is true... oxygen and co does not need supernovas.
(but of course, to get the stuff here in the first place, it needs a stellar explosion)

 

[Bystander]

http://en.wikipedia.org/wiki/Stellar_nucleosynthesis

 

[dubmarine]

thanks hoot , can anyone give me an example of this occurring naturally and spontaneously in order to account for all the water ?

 

[dubmarine]

thanks everyone ! this site rocks !

 

[russ_watters]

I'm not sure the comet theory for water formation on Earth is all that widely accepted. Yes, the universe is nearly entirely hydrogen and helium, but when the sun ignited, most of it was blown away from the inner ring of planets, leaving roughly the proportions of elements we hae now. The Earth was a motlten slurry of what was left, and any free hydrogen still in the atmosphere would have quickly evaporated away into space.

I think it is more likely that the current amosphere and oceans were released through volcanism as the Earth cooled. Being hot, any leftover free hydrogen and oxygen would have readily reacted.

 

[Danger]

I am also certainly no expert in this (wish my old pool partner was here; he's a geology professor specializing in geochemistry), but I believe that free hydrogen is also released after planetary formation from the breakdown of various hydrides, hydrates, et al in both interplanetary debris and the Earth itself. That will, at its first opportunity, combine with oxygen to form more water.

 

[LURCH]

I think the real poser here is where the Oxygen came from. Hydrogen was abundant, on that we are all agreed. It is also well-known that hydrogen will combine with O₂ without much provocation. But where did we get the O₂? Stellar fusion? And if so, would it have been from the sun, or would it need to be previously made in other stars, to make it available early enough and in sufficient quantities to explain current conditions (that last bit seems very probable)?

 

[Danger]

As far as I know, Lurch, oxygen is indeed formed only during advanced stages of fusion, and spread to the interstellar medium by novae or supervovae explosions.

 

[russ_watters]

I think the real poser here is where the Oxygen came from. Hydrogen was abundant, on that we are all agreed. It is also well-known that hydrogen will combine with O₂ without much provocation. But where did we get the O₂? Stellar fusion? And if so, would it have been from the sun, or would it need to be previously made in other stars, to make it available early enough and in sufficient quantities to explain current conditions (that last bit seems very probable)?

The same question would apply to every other element on earth. I think it makes more sense if you look at it from the other direction: Where did all the hydrogen go? It was blown away by the sun, leaving proportions that we now have.

Though oxygen is the most abundant element in the Earth's crust, it isn't terribly out of whack with the quantities of anything else. http://en.wikipedia.org/wiki/Image:Relative_abundance_of_elements.png

 

[LURCH]

The main theory seems to be that the water was present, as water, in the cloud of material from which the system formed. This is taken as one of the evidences that ours is not a first generation star, but is mostly made of debris from previous stars. We've still got mostly Hydrogen, but there are more of the heavier ellements than would be expected from space.

 

[vanesch]

The main theory seems to be that the water was present, as water, in the cloud of material from which the system formed. This is taken as one of the evidences that ours is not a first generation star, but is mostly made of debris from previous stars. We've still got mostly Hydrogen, but there are more of the heavier ellements than would be expected from space.

Yes, that's the point I wanted to make. We are all made of stardust. The material of our bodies (except for the hydrogen) already went through the core of a star (not the sun) - and a heavy one, that is!

Some stuff (all things heavier than iron) were even produced in supernovas - the only known production mechanism of them.

 

[LURCH]

Cool.

Now the other thing I heard this semester was that Earth's early atmosphere was entirely made of Hydrogen and Hellium, but this envelope was blown away by the ignition of the Sun. The reasoning behind this model was that nearly the entire universe is Hydrogen and Hellium, so that's what ProtoEarth must have had in its atmo before the Sun stripped it away. It was only after this that that the current, water-rich atmosphere began to form, with the water being brought in by comets.

This does not appear to make sense. If there was water in the intial dust-cloud to form the comets, then why would there be none for the early atmosphere? Clearly, the dust cloud from which our system formed was not lacking in elliments other than H and He. This planet formed out of carbonatious rock and sillica, the system had enough water and other gasses to form the outer planets and the comets, wouldn't these have been rpesent in the Earth's atmosphere right from the start?

 

[Bystander]

Compare the ratio of ³⁹Ar to ⁴⁰Ar in Earth's present atmosphere to that in carbonaceous chondrites; what can you conclude about the minimum relative molecular masses of early atmospheric components?

 

[DaveC426913]

All the elements up to Iron were formed in early stars known as Population III stars. Heavier elements were formed in Pop. II and Pop. I stars.

Look up star populations and it will detail the creation of all the known elements.