Re: How did Earth get its water?

From: Mike Lorrey (mlorrey@datamann.com)
Date: Fri May 10 2002 - 14:27:17 MDT


Amara Graps wrote:
>
> 2) The Earth formed wet. The Earth must have formed from, and then
> entirely depleted, an ancient supply of water-rich material located
> near Earth's orbit, that now has no modern analog. "Wet-accretion
> Theory". (Righter and Drake, et al.)

I was wondering if the water could have formed, in situ, from hydrogen
ion bombardment from the solar wind prior to the formation of the Van
Allen belts, i.e. when the planetesimal that created the moon struck
earth, it created the conditions for the eventual formation of our
magnetic field, but before this, the earth's upper atmosphere was freely
bombarded by hydrogen ions for at least a half a billion years.

>
> 3) One Large Splash. Earth formed wet, but not from materials within a
> narrow band located a specific distant from the Sun. One body from
> between Mars and Jupiter, a chance encounter, brought the water and
> volatiles to the Earth in one large splash, sparing Mercury, Venus,
> Mars. The large body was derived from a relatively small number of
> Moon-sized bodies that was bombarding the inner solar system.
> "Stochastic Wet-accretion Theory". (Morbidelli et al.)

But what is the cause of the high deuterium content of comets? They've
been bombarded by radiation for several billion years longer than the
earths surface has, therefore comets SHOULD have more deuterium. We
could've been nailed by a lot of early comets that had recent formation
and thus were lower in D.



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