Michael, List,
I think it's most likely that some special
group or unique class may be Mercurians
and less likely that they are not recognized
as meteorites. But we have to remember that
our solar system and everything in it has
been made out of the very same box of Betty
Crocker Complete Solar System Mix; no extra
ingredients need be added.
There was no recognition and proof of the origin
of Lunar and Martians until we had either brought
back a sample (in the moon case) or put down
an analytical lander (in the Mars case). We had
comparison samples of the Moon to analyze
and we had the noble gas isotope ratios for
Mars.
Evidence, in other words, real, physical. Maybe
Messenger will make some unique observation
of a characteristic of Mercury that points an arrow
to a candidate Mercurian stone. Chancy.
Gladman also predicts Venusian meteorites, but
his simulations do not take into account the dense
Venusian atmosphere and its potential to suppress
ejecta. But a big impact blows out the atmospheric
column above it and lets ejecta escape. But the problem
of whether Venusian ejecta could escape the planet is
murky, at best.
If they did... The problem is that Veusian basalt is
probably indistinguishable from terrestrial basalt
unless you look real close and who would?
So you are certainly right -- the biggest best clue
would be fusion crust, the fresher the better.
Sterling K. Webb
------------------------------------------------------------------------
----- Original Message -----
From: "Michael Fowler" <mqfow...@mac.com>
To: <meteorite-list@meteoritecentral.com>
Cc: "Michael Fowler" <mqfow...@mac.com>
Sent: Thursday, August 04, 2011 9:10 PM
Subject: Re: [meteorite-list] Mercury Fragments on earth (not)
Perhaps, Sterling, you are saying we should keep an open mind.
I don't totally disagree, but....
There are some things that can help distinguish a meteorite from other
rocks, no matter where it comes from.
Number one: It will have or had a fusion crust.
If you take the number of Martian meteorites found with at least some
fusion crust, then according to the authors calculations there should
be 1/2 to 1/3 as many Mercurian meteorites found also with fusion
crust. If so, they should already have a class established like SNC,
even if we don't know where they are from. Keep in mind that we
thought the SNC meteorites were in some way special, long before we
were certain they were from Mars.
Were you saying a Mercurian meteorite won't be recognized as a
meteorite or just that we won't be able to tell if is from Mercury?
Mike Fowler
PS At the time when we could have said there are no lunar meteorites,
the total number of meteorites known was about 7,000 compared to
todays totals of maybe 100,000 and growing! When a science is in its
infancy, obviously there are many things yet to discover.
There was a time when you could say: "The fact that
Lunar meteorites have not been found on Earth is
prima facie evidence that there are none."
There was a time when you could say: "The fact that
Martian meteorites have not been found on Earth is
prima facie evidence that there are none."
Humans have stared at both and had no idea of what
they were looking at. Martians were frequent enough
to get and maintain a class all their own for centuries
before we knew, and Lunars we probably just tossed
over our shoulders without a thought.
I say:
This is a time when you (or I) can say: "The fact that
Mercurian meteorites have not been found on Earth is
prima facie evidence that we can't recognize them!
We don't know what they are. We are probably quite
wrong about what to expect."
Sterlng K. Webb
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