On a sunny day (Sun, 13 Dec 2009 01:42:52 -0500) it happened Yousuf Khan
wrote in :

Jan Panteltje wrote:
On a sunny day (Sat, 12 Dec 2009 16:55:27 -0500) it happened Yousuf Khan
wrote in :

Two separate studies are claiming that Earth's two most prominent
surface fluids, air and water, came not from within but from outer
space. I have my doubts about these studies' conclusions, it seems like
a stretch that there could be enough air and water brought from meteors
that are being randomly hurled toward the inner solar system, especially
when the vast majority of them are likely heading towards the Sun.

Yousuf Khan

It is obvious in a way, and I think this is correct.
It could also mean earth gained volume long ago, gained a lot of mass,
and the heavier creatures could not handle the gravity and died.
My speculation :-)
That could have happened much later, impacts of one or more a huge ice balls.

I have no problem accepting that the original air and water came from
the meteors and planetesimals that formed the Earth at the beginning, as
there was plenty of material to go around at that time. And the Sun
wasn't as much of a target within original nursery dust cloud, as it too
was forming at that time.

But after formation, things must have gotten a bit more static in their
mass ratios. Any asteroids and comets coming towards the inner solar
system were likely hitting the objects of the inner solar system (i.e.
the terrestrial planets & the Sun) based on the ratio of these objects'
masses.

So when things were a bit more mixed up during formation, these items
had more chance of getting to every object as they formed.

Basically, it's more likely the chemicals arrived during formation than
during late heavy bombardment.

Yousuf Khan

If you look at very old maps of the earth, you will see the continents
sort of glued together.
Those are now apart, due to continental drift they say.
In the middle of the oceans between those continents there is
a volcanic ridge still spewing out material.
It could also be that some giant body impacted and increased the earth mass,
blew it up like a balloon, and caused the oceans and the separation of the continents,