Re-2: [meteorite-list] Moss Meteorite From A Comet?

From: Larry Lebofsky <lebofsky_at_meteoritecentral.com>
Date: Mon Aug 21 08:44:22 2006
Message-ID: <1156164255.44e9aa9f3a75d_at_hindmost.LPL.Arizona.EDU>

Hi all:

Defending Tim Swindle and Humberto Campins. I have known them for years and
they are very conservative scientists. Their work is good and they are well-
respected scientists. They do not go off (too often) to make wild,
unsubstantiated, claims., hence, the conclusions in their article. They based
their Meteorite paper (and their original scientific paper) on what we know.
We have observations of many comets (Campins has done a lot of this), but we
have "samples" from only one comet (Halley), are just now studying Stardust
material (so too early to say much), and IDPs which are thought to be, at
least in part, cometary in origin.

Clearly, we need multiple samples from multiple comets --- good luck in our
lifetime. Therefore you base your "theories" on the existing information, not
onwhat you hope to have in the future. That is why people propose new missions
to comets and asteroids!

We know that not all comets are the same based on our observations and where
we think they came from. Some of this may be because of how many times they
have been close to the Sun, some may have to be related to where they came
from (Kuiper Belt or Oort cloud), and some may have to do with where they were
formed (which may not have been where we see them coming from). Clearly, a
chunk of a "fresh" comet would look very different from a "dead" comet. Or, as
been on this listserv recently, could we tell the difference between a chunk
of a comet or a piece of Ceres? I am not sure I would be willing to say
anything in print even though I have studied Ceres for years. What, from
either, would we expect to make it through the atmosphere?

Even if we were to bring back samples from two or three comets, I doubt if
anyone I know would be willing to say (with respect to the composition of
comets) that that was their "final answer." That is the nature of science.

I really have to stop writing these a 5:00 in the morning, no breakfast and no
soffee, but this is the quiet time of the day.

Larry



Quoting bernd.pauli_at_paulinet.de:

> "Comets ... being 'primitive material' ... we would need
> to have known multiple samples of multiple comets before
> we could say for sure."
>
> Hi Mark and List,
>
> I couldn't agree more and that's why I felt a bit uneasy when I read
> Campins' and Swindle's article in this issue of our METEORITE magazine:
>
> CAMPINS H. and SWINDLE T.D.(2006) Where are the cometary
> meteorites? (Meteorite, May 2006, Vol. 12, No.2, pp. 17-19).
>
> They solely refer repeatedly to Comet Halley and to Halley dust (plus to
> cometary IDPs). Many more comets need to be sampled before we can draw
> definite conclusions!
>
> Best,
>
> Bernd
>
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Received on Mon 21 Aug 2006 08:44:15 AM PDT