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Comment by GMali | Hacker News Reader

How likely is it that this sphere of water actually collided with our Earth billions of years ago? What is the possibility of even more such "water meteoroids" flying around nearby galaxies?

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Water does not stay liquid in a vacuum. It is either solid or gaseous, depending on the ambient conditions. It is not well established where the primordial Earth gained its water. The matter in the protoplanetary disc from which the Earth coalesced probably didn't contain much water or other volatiles because of the proximity to the Sun. Instead, it is thought that water arrived afterwards, via numerous collisions - then commonplace - with icy comets that originated beyond the frost line.

http://en.wikipedia.org/wiki/Frost_line_%28astrophysics%29 http://en.wikipedia.org/wiki/Origin_of_water_on_Earth

Would a sphere of water that size be massive enough to hold a gaseous atmosphere heavy enough to allow liquid water far enough down?

With a diameter less than half of the Moon, and with a mass only 1/50 of the Moon, I think it's quite unlikely.

Volcanoes emit a lot of water aren't they? I've heard more than half of the emission is water vapor.

Yes, sort of. I believe the current theory is that much of Earth's water came from thousands or millions of meteorites that carried ice and/or hydrogen and oxygen compounds that later stabilized to water. This would have happened during the solar system's infancy, when there were far more asteroids flying around our solar system. In fact, it is thought that the planets started this way. Lots of free flying rock colliding together, gaining mass, gravity, etc. over billions of years.

Why the downvotes? It's an interesting question.

They're called comets.

Some theories are that the bulk of the Earth's water did in fact arrive in this form.

According to the History Channel, aliens brought it here.

This is not reddit. Please use the comment section to seriously discuss about the topic in question. Thanks!

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