[meteorite-list] Solar Wind and Meteorites

From: Walter Branch <branchw_at_meteoritecentral.com>
Date: Mon Feb 21 23:32:25 2005
Message-ID: <004901c51896$f03b3420$6101a8c0_at_launchmodem.com>

Hello,

I was just catching up on the February, 2005 issue of
Sky and Telesope and in it, there is an interesting article
on the Sloan Digital Sky Survey. On page 36, the article
mentions solar-wind discoloration of asteroids. I have
sometimes wondered whether the solar wind affects the
color of asteroids to the degree that the surface colors
might be affected and differ from the internal matrix
of freshly fallen meteorites. To quote from the article:

Collisions aren't the only processes that alter asteroids.
Planetary scientists have predicted that asteroid colors
should evolve as the rocky objects surfaces are altered by
the solar wind and by the micrometeroid impacts. The Sloan
asteroids' colors and orbital parameters support this
"space weathering" hypothesis (S&T: October, 2004, page
26). They also solve a long standing mystery: why
the interiors of meteorites that have fallen to Earth have
colors that differ from those of commonest asteroids.

Follow-up questions would be:

Is the degree of space weathering dependent upon the
type of material (e.g., iron, common chondrite, carbonaceous,
etc.)?

How does that affect spectral reflectance studies?

Can the effect be reproduced under laboratory conditons
(greatlly speeded up, of course).

How deep does the discoloration go. I would think only a
few mm below the surface yet I know there are meteorites
that have solar wind discoloration (I had a list somewhere, but
now I can't find it). How does this survive the ablation process?
Perhaps these are brecciated chondrites that were solar wind
exposed then subsequently experienced impacts, then re-accreated.
For example, would we be more likely to find solar wind
discoloration in Howardites?

Any know?

-Walter Branch
Received on Mon 21 Feb 2005 11:28:20 PM PST