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Re: Ibitira update
I had a nice chat with Michael Casper, who has the main mass
of the Ibitira meteorite. He says there is no reason to believe that
Ibitira is a Mars meteorite. He also pointed out that Ibitira is
not the only achondrite known to have vesicules. Juvinas also
has vesicules, though not in the quantity Ibitira has.
Juvinas is the world's largest eucrite (91kg!), which fell in
France in 1821. So, there is at least two vesiculated eucrites known.
Also, in case you didn't know, the parent body of all eucrites is strongly
suspected to be the asteroid
Vesta. This is based on spectra which match up surprisingly well between
eucrites and Vesta. Hubble Space Telescope images of the asteroid
also shows evidence of lava flows, which fits in well with eucrites
since they are basaltic rocks.
Also, after some digging around, I found out the cosmis ray age of
the Ibitira meteorite is only about 10 million years. Combine this with the
meteorite's age of 4.5 billion years, and you can rule out the Earth
as being the source of the meteorite. The oldest known rocks on the
Earth are 3.8 billion years old, so an impact on Earth 10 million years
ago could not have launched a 4.5 billion year old rock into space.
Ron Baalke
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