[meteorite-list] Astronomers Lean Toward Eight Planets

From: MexicoDoug <MexicoDoug_at_meteoritecentral.com>
Date: Fri Aug 25 17:46:18 2006
Message-ID: <00a801c6c88f$cef6d800$29cf5ec8_at_0019110394>

Yes, Sterling, as Larry mentions, carbonaceous chondrites have been proposed
as questionable yet decent matches for Ceres, though others add that
primitive achondrites are where it is at and that the biggest inner minor
planet is somewhat differentiated. Looks like there aren't any especially
prominent silicate signatures in Ceres' spectrum, and I do see that the
literature has shown heating has a big effect the interpretation of the
artifacts that characterize the spectra. I.e., the match gets a little
better if you cook the hell out of Murchison CM2 meteorite powder (up to
1000 C) and then compare it to Ceres, formerly known as a G-class anomalous
asteroid. But we need more information to be sure and that is in the
pipeline with NASA's Dawn mission. So, silicate composition for Ceres are
not a given, nor a prominent feature on Ceres reflectance spectrum, and
while I haven't looked into it, I suspect that might be a modified but
similar case for KBOs like Pluto, though I confess not reading anything on
the current state of knowledge there.

Refs:

Hiroi, T., Searching for the parent bodies of meteorites through reflectance
spectroscopy: Current state. Evolution of Solar System Materials: A New
Perspective from Antarctic Meteorites, 38-39 (2003).

 T. Hiroi, C. M. Pieters, M. E. Zolensky, and M. E. Lipschutz, Evidence of
thermal metamorphism on the C, G, B, and F asteroids. Science 261,
1016-1018, (1993).

You can download these articles here:
http://www.planetary.brown.edu/~hiroi/Publicat.htm

Oh and don't miss these early abstracts, maybe someone could give us a hand
with them:
Freierberg, M.E. and L. Lebofsky, Icarus v. 63 p. 183 (1985).
Jones, T. Lebofsky, L., Lewis, J., and M. Marley, Icarus v. 88 p. 172
(1990).

Best wishes, Doug


Larry wrote:

> With a density of just over 2.0, there is a lot of water in Ceres. It is
> assumed to be all below the surface (as water ice is not stable on its
> surface), but it is a good match to CI and CM meteorites and so has a good
deal
> of water in it. So, it is most likely a very wet rock.
>
> From the HST images, which show white spots, it may even have some water
ice on
> its surface. I would be thrilled with that since I "predicted" ice on
Ceres and
> then showed that it could not have any since it is too warm. More recent
work
> has show that my observational analysis may not have been too far off
(Dawn
> will give us the answer).
>
> Larry
>

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Received on Fri 25 Aug 2006 05:45:36 PM PDT