APOD: The Comet Hartley 2 Cruise (2011 Oct 07)

[Case]

NGC 2438

http://apod.nasa.gov/apod/ap110407.html
ap090326, ap060910, ap050804, ap990305
ap030614, ap011003

[iamlucky13]

The oceans are big. Really big. And really, really deep. I find it hard to believe that all of that water came from comet impacts. And if they did, wouldn't comets of that mass cause planetary deformation sufficient to have reheated its surface to vaporizing temperatures again?

The Late Heavy Bombardment is believed to have occurred around the time the earth developed a solid crust. This could have delivered huge quantities of water to earth, and while it would potentially have mostly been vaporized as you suggest, between the earth's gravity and the lower solar output of the early sun, it is quite possible for much of the water delivered by such comets to be retained.

I think it's worth pointing out that even today literally billions of tons of water are vaporized per day (evaporation = vaporization), but only very trivial amounts of it are lost to space.