The pairing numbers are based on the abundances of non-OC's.<As for rare meteorites, which I will define as non-ordinary-chondrites, there are 1550 from Antarctica and 467 from commercial collections.>
Let's refine the numbers a bit. Pretty much the start of hot desert collecting was in 1998. Of the numbers you quote above how many are since the start of 1998? Do the same pairing numbers Lindstrom estimated apply to the non-ordinary-chondrites? I don't have access to a database so Jeff if you could let us know I would appreciate it.
Since 1998, it's ~5:3 by number and 10:1 by mass in favor of commercial meteorites for rare types. The total is ~500 rare meteorites.
<Meteorites that formed strewn fields get just as many numbers in the Sahara as in Antarctica (one per specimen).>
I was under the impression that each specimen gets a separate designation in antarctica. If there was a witnessed fall in Antarctica such as bensour in Africa would it get a single name and entry in the catalog listing or would each stone found get a separate designation and entry?
Each stone in BOTH places gets a separate designation. However, as I said, many Saharan meteorites are found as piles of rubble, so the reported number of pieces is high for some. Of course there are a few recent showers in Africa that have a single name. Observed falls in Antarctica would be treated the same as anywhere else: no numbers.
I can't make that estimate. That is one of the reasons that I asked about
the total
mass of Antarctic meteorites. Statistically it would be reasonable to
assume the
ratio of OCs to other meteorite types would be similar. Certainly
differences in weathering will affect the numbers some, but in gross approximation they
should
be somewhat similar. If there is 10 or 100 times as much mass coming out of
the hot desert there should be 10 or 100 times the rare stuff, or at least 2
to 20 times. High mass strewn fields certainly could affect the statistics
however neither region has many iron meteorites which would be most likely
to affect the approximation. Stony falls aren't big enough that one fall
should
affect the gross approximation that much.
Well, the mass issue is messy. By and large, small stones are not collected in Africa. Or at least, the ones that are never get looked at unless somebody thinks they're special. This is why the mass ratio of rare types is so much greater than the number ratio in the statistics above. The median size of commercial stones of rare types is ~160 g, whereas the same number for Antarctic ones is ~18 g. In Antarctica, all of the gram-sized stones have been collected (including many "main masses" in this size range!). So you're looking at an incredibly size-biased Saharan collection, and an Antarctic collection that more closely represents what actually falls. I think the Antarctic collection has about the correct number of irons (after correction for pairing) based on fall statistics . The Saharan material has been scavanged by man over the centuries, and the irons are apparently long gone.
Of course, in terms of importance to science, the high mass of African/Omani meteorites is not the important issue. Most specimens of these that are deposited in scientific collections now weigh 20 g or less. This is a very hard number to get stats on, but I counted the Libyan and NWA's in the latest bulletin and found that the median size of rare meteorites deposited in collections is on the order of 15 g, which is actually about the same as the median Antarctic size. The rest is eventually destroyed as far as many scientists are concerned, or at least badly compromised. We can do a lot with a few grams (as we have always done with Antarctic meteorites), but future researchers will have precious little material to study, and nobody gets the chance to study hand-sample scale features once the specimen is sliced into a million bits. For Antarctic meteorites, this is the hand we were dealt. But for warm deserts, it is a sociological phenomenon. These are the reasons why many scientists resent commercial meteorite ventures. To me, this situation is a compromise that we can all live with, considering the bad alternatives on both sides (read my editorial in MAPS from 2 years ago).
On the subject of this whole thread, I don't know of very many scientists who would say something as silly as "commercially collected meteorites have little scientific value." Where in the world did this idea come from? Somebody should count the abstracts from Muenster and see how scientists "voted with their feet" on this idea. The main problem some museum scientists have is caused by their worry that many of these meteorites are smuggled out of their countries-of-origin, and therefore adding them to their collections is unethical, if not illegal.
jeff
Eric Olson http://www.star-bits.com
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Dr. Jeffrey N. Grossman phone: (703) 648-6184 US Geological Survey fax: (703) 648-6383 954 National Center Reston, VA 20192, USA
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