[meteorite-list] Comets as meteorite source

From: E.P. Grondine <epgrondine_at_meteoritecentral.com>
Date: Mon Aug 21 10:16:06 2006
Message-ID: <20060821141603.99202.qmail_at_web36914.mail.mud.yahoo.com>

Hi all -

This is my coverage from several years ago of a
presentation by Binzel:

Rick Binzel presented a summary of what is currently
known about the properties of all asteroids, including
the threatening ones. Generally, the percentage of
each type of asteroid matches well spectrally with the
differing percentages of the types of meteorites
recovered on Earth:

ASTEROID TYPE METEORITE TYPE
PERCENTAGE

Iron:
M-Type Iron 4%

Stoney Iron:
A-Type Stoney Iron 1%

Stones: 95%
Achondrite: 9%
Vesta-type Basaltic Achondrite 9%
Chondrite: 86%
S-Types Ordinary Chondrite 81%, when
spectra adjusted for space weathering
G-Type Carbonaceous Chondrite 5%
usually assumed to be dead comet fragments

These data indicate that the mechanism for the
ejection of meteorites works uniformly across all
classes of meteorites.

The problem that emerges is that the measured
densities of the meteorites are far greater than the
estimated densities for the asteroids, and this low
porousity and crushability of the asteroids generates
problems for most means of stopping them from hitting.
The same problems appear to hold true for the means of
handling in-bound comets as well.

end quote

The question at hand is what are the carbonaceous
chondrite parent bodies. For the G type Binzel
assumed cometary - I think Clube and Napier would
probably include more than that. Berndt, can you use
your database to track G type over to carbonaceous
chondrite types?

I suspect that when the larger craters are examined to
determine what hit, we will have a better grasp on
comets as a meteorite source.

By the Brown Ammendment, this study is now NASA's
formal responsibility, but I expect Griffin et al. to
try and weasel their way out of it. Another snag -
USGS has the technical know-how to do these studies,
NASA does not.

IMO, What it comes down to is moving Morrison to
retirement. Then NASA proceeds. I was saddened to
learn that M. managed to get the chair of the new IAU
impact committee.

Or we can wait until 2018, when China to steps in.

good hunting,
Ed

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Received on Mon 21 Aug 2006 10:16:03 AM PDT