[meteorite-list] Meteorite location data

From: Matson, Robert <ROBERT.D.MATSON_at_meteoritecentral.com>
Date: Thu Apr 22 09:44:13 2004
Message-ID: <AF564D2B9D91D411B9FE00508BF1C8698E54B9_at_US-Torrance.mail.saic.com>

Hi All,

I would like to add to the Pelisson's list of reasons why
meteorite fall location data is important:

5. In areas subject to deflation, you may discover overlapping
strewnfields from two or more falls. In this case, the vertical
axis (depth) which correlates to time, has been compressed to a
plane, in which case meteorite find proximity is no longer a
strong argument for pairing. Knowing the locations of all finds
in this case may allow you to unravel the mix.

6. Suppose a large number of similar looking chondrites are
found by one group, and 3 or 4 of them are analyzed and classified
as L6's with matching fayalite percentages. That group would
probably naturally assume that all the stones are L6's, and
leave it at that. Now suppose a second group at a later time
independently finds more chondrites from the same general area,
gets several of them tested, and they all come back L4's. They'd
naturally assume the balance of their finds are also L4's.
Without find locations to correlate with the prior L6 finds,
neither group would be aware of the possibility that they
probably have a mix of BOTH types. Or worse -- that the L4's
and L6's are actually from the same fall, and that they've got
a breccia. In this case, the lack of location data might prevent
the search for and discovery of a "Rosetta" stone exhibiting
both clasts that ties the two classifications together.

Despite the obvious benefits of meteorite location information,
successful recovery (even without location data) is ~generally~
preferable to no recovery at all. I say "generally preferable"
because there are a couple of instances where it would be better
to leave a meteorite in place (even to weather further) than
for a hack to remove it. For example:

1. A relatively freshly fallen Mars meteorite (or even a
volatile carbonaceous chondrite like Murchison). In this case
the location information is important for the recovery of any
additional specimens from the fall. But more important is
the issue of contamination or degradation. An expert recovery
can avoid direct human contact and minimize any further terrestrial
contamination. This can greatly enhance the scientific value of
the specimen. One caveat, however, is in the case of the threat
of imminent severe degradation (i.e. rain) or loss (e.g. Tagish
Lake). Here, the value of a minimally contaminated specimen must
be weighed against its outright loss.

2. A large strewnfield of L6 or H5 meteorites. Here we've got
a case where the location data is actually more important than
the meteorites themselves. Another 20 kilos of equilibrated
ordinary chondrites is not likely to provide the key to any
new scientific insights. But a careful recording of masses
and locations can tell you the direction of travel. That axis
may in turn coincide with a previous (or future) find allowing
for pairing. And who knows? The find location and direction
of travel may correlate with a prior bolide observation, turning
the find into a fall, and potentially allowing reconstruction of
the orbit of the parent body.

So in summary, find location data can be extremely valuable,
but in many cases the meteorite without this data is more
important than no meteorite at all.

Cheers,
Rob
Received on Wed 20 Jun 2001 03:07:20 PM PDT