Why does Earth have so much water? - Do you know?

clark · 2003-12-08 12:23:44

Pondering something...

Why does the Earth have so much water in realtion to it's size, and in comparison to the rest of the solar system's planets?

Where did all the water come from? When?

Now, I admit, this is a set-up, since I am testing the plausibility of a little pet theory... which means I am more than likely wrong. So, please help show me.

So : Formation of the moon is believed to have occured (at least according to some theories) by a passing planetary size body colliding with Earth. Some people think it might have been Mars, or a Mars sized planet that hit Earth.

Could it be at all possible that Mars collided with Earth, causing the Moon to be created, and also deposit some of it's own water onto Earth?

Mars, would then have continued out to it's eventual position, sans a great deal of it's own water. This would then lead to a false-start of a life sustaining atmosphere on Mars since it lacked a sufficient amount of water.

Mars, dry as a bone... with earth 2/3 covered in water....

~Eternal~ · 2003-12-08 13:18:03

Mars is dry, but it certainly does not lack water :b.
Alotta planets and moons have water in ice form,
Mercury, Mars, the Asteroids contain some ice, comets, Ganymede, Callisto, Europa, Titan(?), and Oort cloud objects might contain ice.

Euler · 2003-12-08 14:17:29

Scientist currently believe that most of Earths water came from small icy meteoroids that bombard the Earth's atmosphere. Earth appears to have much more water than any other planet because it is the only planet with the correct temperature for liquid water.

jadeheart · 2003-12-08 15:19:46

link for ya

...talks about what may have happened to venus's water. basically it implies venus' proximity to the sun indirectly (read article for details) led to UV dissociation of H from O in the upper venutian atmosphere; the H escaped to space. there seemed to be a little uncertainty as to what happened to the O. there're even a couple of sentences about the possibility that life arose on the early venus.

you could further this conjecture and imagine that the reason mars was able to keep as much water as it has was because of its distance from the sun-- the water froze out before it was lost via UV dissociation. something future terraformers will probably want to keep in mind.

so i guess the answer to your question is that all the interior planets had plenty of water early on, but lost it or kept it depending on their unique circumstances.

hope this helps

Spider-Man · 2003-12-08 22:57:44

Earth appears to have much more water than any other planet because it is the only planet with the correct temperature for liquid water.

Thank you, yes. Earth actually should, proportionally, be almost totally covered in water (Europa, for instance, has more water than the Earth, even though her mass is only 5/7 that of Luna). But, as noted, the Moon was formed when a Mars-sized protoplanet collided with the Earth, blasting off much of the water into space (leaving us continents), the denser ejecta shaping into Luna (and doesn't she look beautiful tonight! especially her light upon the new-fallen snow in the American Northeast).

Shaun Barrett · 2003-12-09 02:23:11

Hi Clark.
I've never seen any reference to the 'Mars-size' impactor, which is our current best explanation for the existence of the Moon, perhaps actually being Mars itself.

As far as I know, all the computer-simulations of the impact event which give us roughly the 'correct' outcome (i.e. position, density and constituents of the Moon as we see them today etc.), also result in the destruction of the impactor itself.
The core and much of the mantle of the impactor sink into the proto-Earth, adding to the size of the iron core and increasing Earth's density and gravitational field. A remnant mixture of upper mantle and crustal material from both bodies sprays out into space, ultimately coalescing to become the Moon.
Personally, I can't conceive of a scenario whereby Mars itself could have struck Earth, created the Moon, lost much of its water to Earth, ricocheted off on a modified path, and taken up residence where it is today. (But then, I thought we'd have people on Mars by now ... so what do I know, right?! )

A similar but perhaps less violent collision, though, might go a long way toward explaining the lower, younger, relatively crater-free northern hemisphere of Mars. A major collision might also help to explain Mars' axial obliquity and its comparatively eccentric orbit.

So many questions; so few answers!

clark · 2003-12-09 11:03:03

Excellent! Thank you all for pointing out how wrong this premise is.

Personally, I can't conceive of a scenario whereby Mars itself could have struck Earth, created the Moon, lost much of its water to Earth, ricocheted off on a modified path, and taken up residence where it is today.

It is indeed a fanicful supposition, which is arrived at by surface observation. Science, for better or worse, often takes the romance out of what our imagination can conceive.

So Earth ate up the impacting planet? What is the current explanation for the weird difference in elevation on Mars (between the northern and southern hemisphere- Olympus Mons, the fractures on the opposite side?)

When do they think the moon was formed?

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#1 2003-12-08 12:23:44

Re: Why does Earth have so much water? - Do you know?

#2 2003-12-08 13:18:03

Re: Why does Earth have so much water? - Do you know?

#3 2003-12-08 14:17:29

Re: Why does Earth have so much water? - Do you know?

#4 2003-12-08 15:19:46

Re: Why does Earth have so much water? - Do you know?

#5 2003-12-08 22:57:44

Re: Why does Earth have so much water? - Do you know?

#6 2003-12-09 02:23:11

Re: Why does Earth have so much water? - Do you know?

#7 2003-12-09 11:03:03

Re: Why does Earth have so much water? - Do you know?

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