From: LARRY KLAES (ljk4@msn.com)
Date: Fri May 17 2002 - 08:46:53 PDT
(8) MERCURY METEORITE PUZZLE
>From BBC News Online, 16 May 2002
http://news.bbc.co.uk/hi/english/sci/tech/newsid_1991000/1991394.stm
By Dr David Whitehouse
BBC News Online science editor
The first meteorite that may have come from Mercury has been identified.
NWA 011 was found in the Moroccan Sahara in December 1999 and was
immediately regarded as something unusual.
It clearly had a molten past and was formed from lighter materials than most
meteorites. This implied it had once been part of a much larger body.
It was originally classified as a eucrite, a group of meteorites thought to
be from the asteroid Vesta. But a detailed analysis of NWA 011 showed it to
be different.
Now, researchers speculate that it is the first known meteorite from our
Solar System's innermost planet, Mercury.
Rocks blasted off Mercury by a large impactor would have a difficult journey
to reach the Earth, say the researchers - but not impossible. Nevertheless,
the calculations show such rocks would be an extremely rare find on Earth.
NWA 011 has an oxygen isotope ratio that indicates it came from a body
larger than a big asteroid.
Japanese researchers say the basalt in NWA 011 suggests the body from which
it did originate had a core of molten iron with an outer covering of silicon
and aluminium that formed a basaltic crust.
And that means a planet-sized body. Could it really be Mercury?
Copyright 2002, BBC
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