[meteorite-list] Recognizing a Venusian meteorite

From: Popocatept_at_aol.com <Popocatept_at_meteoritecentral.com>
Date: Thu Apr 22 10:28:35 2004
Message-ID: <195.216dee21.2cc9ed53_at_aol.com>

Sterling,

Interesting theory about Venus's atmosphere being blown off by a monster
impactor. Here is my objection: Where did the 100 bar carbon dioxide atmosphere
come from? Could one monster impactor blow off the existing atmosphere and
yet at the same time deposit a new one? Seems a stretch.

I suggest a different scenario. Mars is enriched in Argon 40 compared to
earth for the same reason it is enriched in deuterium. The lighter elements are
lost to space as a function of Mars's lesser gravity.

Venus has a tremendous amount of CO2, Argon 36 neon, etc, because it
atmosphere was not blown off into space by a giant impactor.

On the contrary it was earth's atmosphere that was lost to space.
Therefore using Earth's ratio of Ar 36/40 as a standard is misleading. What
was the giant impactor responsible for the loss of earth's atmosphere. A good
candidate is the impactor that created the moon.

In any case, a young crystallization age of less than 500 million years would
eliminate all sources, except Venus and Mars.

Mike Fowler



"E.J" wrote:

> Howard Wu wrote:
> > Still the question was how would we recognize a venusian meteorite?
> Great question to ponder.

    The best way to identify a Venus Stone would be by the Argon isotope
ratios. Argon-36 is the "natural" original isotope of Argon from the solar
nebula. Argon-40 is formed by the radioactive decay of Potassium. It forms in
the stone body of a planet and is released to the atmosphere by volcanic
action, or "out-gassing."
    On Earth, most of our Argon is isotope 40, thanks to our active little
rockball, and there is very little "natural" Argon. The 40:36 isotope ratio is
296 to 1. On Mars, there is even less "natural" Argon. The 40:36 isotope ratio
for Mars is 2750 +/- 500 to 1 (Is Mars more volcanic than the Earth? Hmmmm.).
So far, it all fits with those nice theories about volatiles and nebulas
(which, you call tell by my tone, I distrust profoundly).
    Therefore, we would expect a ratio of 200:1 for Venus or maybe even 100:1,
right?
    Here's where reality gets in its licks. First, there's 50 to 100 times
more Argon and Neon in Venus' atmosphere than we would expect, huge amounts!
Where in the H*** did that come from? Second, the 40:36 isotope ratio is 1 to
1, more or less. That is, they are present in roughly equal amounts.
    Say what? Well, maybe all the noble gasses are enriched? Nah, they're not.
This demonstrates that the abnormal Argon did not come from the "old" solar
nebula. The two "explanations" left and they're both whacky: 1) Venus has no
Potassium in the planet at all, so there is no Argon 40! This goes against
everything. No Potassium!!! That's Crazy. And 2) Venus has never had any kind
of volcanic activity at all, ever, period. That's even Crazier, since we can
radar-map a huge of what appear to be volcanic features on Venus.
    My personal theory is that Venus had its entire native atmosphere blown
off by a whopping big impactor 480,000,000 years ago, an impactor that
completely melted Venus' crust, resurfaced the planet, and left a lot of its
own volatiles behind as a new atmosphere to mix with the residues of the
melted crust. Hey, I said it was whopping big, didn't I?
    So, what you do is a rare gas analysis of the suspected Venus meteorite,
and if the Argon 40:36 ratio is the same, then Venusian meteorite is its name,
as Johnny Cochran would say.

Sterling K. Webb
Received on Thu 23 Oct 2003 10:49:55 PM PDT