From: Mike Lorrey (mlorrey@yahoo.com)
Date: Sun Feb 02 2003 - 15:10:04 MST
--- avatar <avatar@renegadeclothing.com.au> wrote:
> Mike Lorrey writes:
>
> Yes, and it wouldn't really take that large a moon to allow an
> > Earth-like environment. Keep in mind our atmosphere is so thin
> because
> > of billions of years of carbon sequestration that followed an
> impact
> > event that stripped much of earth's original lithosphere, which now
> > forms most of the moon. Saturn's moon Titan has an atmosphere
> several
> > times denser than ours, and this is WAY out there, where the
> surface is
> > thick with precipitated atmosphere.
>
> Hold on. I thought our atmosphere was retained because of our
> magnetosphere (preventing the solar wind from stripping it) [possibly
> in turn due to our liquid iron core surrounding the solid iron core].
> It's complicated because of internal radioactive mechanisms and an
> active planetary matrix cuasing some production of atmosphere,
> combined with water dumped from meteorites.
No, the magnetosphere has little to do with atmospheric retention other
than reducing the amount of radiation we receive.
>
> I'm been trying to get a handle on this with Earth vs. Venus vs. Mars
> and the varying conditions. Also of course as Mike says the influence
> of the x-body and the proto-Earth body that resulted in the
> Earth-Moon system and its chemical peculiarities.
>
> All I can say is that some sources claim the atmosphere would have
> been nearly completely stripped away, however it was generated, by
> the solar wind were it not for the active magnetosphere.
This is simply not true. Venus has little or no magnetosphere, yet it
retains 92 times more atmosphere than we have, PLUS it is half the
distance to the sun, so it gets much more solar wind per square inch
than we get.
Jovian planets are almost entirely atmosphere, yet solar wind does not
strip them away either.
>
> I am still trying to read upon on the explanations for the
> pecularities of Venus.
If life had not evolved here, the earth would have 50 times more
atmosphere than it has now. Most of our original atmosphere is now
locked up as limestone rock. If the moon was not there to cause our
active tectonics, life would have turned our atmosphere almost entirely
into rock as it once did to Mars. Instead, tectonics, as well as other
biological processes recycles some of the limestone back to the
atmosphere. Enough CO2 is there to retain some solar energy at the
surface, but not enough to block thermal radiation entirely.
Venus' atmosphere is so dense that its albedo is so high that it
actually absorbs LESS heat than Earth does, it just holds on to far
more of what it does absorb.
I suggest those interested Fogg's textbook "Terraforming Planetary
Environments" to become informed on the subject.
=====
Mike Lorrey
"Live Free or Die, Death is not the Worst of Evils."
- Gen. John Stark
"Pacifists are Objectively Pro-Fascist." - George Orwell
"Treason doth never Prosper. What is the Reason?
For if it Prosper, none Dare call it Treason..." - Ovid
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