I don't think total mass is a useful number because the statistics are dominated by a few outliers. You really have to go to pairing-corrected statistics. Lindstrom estimated that the average pairing group among antarctic specimens is ~5, which lowers the total number of separate Antarctic meteorites to about 4000. There are many pairings also among commercially collected meteorites, although I don't know if anybody has estimated the ratio in the same way as Lindstrom did. The average pairing group among separately collected meteorites has got to be at least 3, I would guess. So you take the 4000 or so commercial meteorites, and let's allow an equal number of unclassified/undescribed stones, making 8000. Divide by my conservative 3, and you still have >2x as many unique Antarctic meteorites as commercial ones. But let's face it... you can't get even close to statements that were made indicating that 95% of new meteorites are commercially collected ones.
As for rare meteorites, which I will define as non-ordinary-chondrites, there are 1550 from Antarctica and 467 from commercial collections. So the ratio of antarctic:commercial meteorites is 3:1 instead of the raw number of 3.5:1 among total meteorites, enhanced by the "high-grading" that goes on in the commercial sector. Commercial meteorites are still overwhelmingly ordinary chondrites.
jeff
At 01:30 PM 8/8/2003, [EMAIL PROTECTED] wrote:
Jeff Grossman wrote:
<70% of all known meteorites are Antarctic 20% of all known meteorites have been collected commercially. The remaining 10% include all the falls and sporadic finds throughout history.>
I respectfully disagree. The naming conventions tilt those numbers significantly toward the antarctic meteorites. In antarctic collecting every individual is given its own designation unless it is a fragment of a closely associated stone. All of these individuals are eventually classified even if 80% of a collection year are obviously related L5s. If every individual coming out of NWA were given its own designation the numbers would completely dwarf the antarctica numbers. In most cases a single stone is classified as representative of itself and possibly hundreds of other similar stones. NWA 801 CR and NWA 869 L5 are examples that come to mind. In addition while all the antarctic meteorites will eventually be classified this is not even close to being the case for hot desert meteorites. Due to lack of instrument time, money, and priorities on rarer meteorite types, many, if not most, ordinary chondrites from NWA will never be classified. That is not a criticism, just reality. Those NWA meteorites that are classified are predominantly the rarer types. A much more realistic determination would be a comparison of different rare types of meteorites. The mars compendium for instance lists 11 hot desert, 10 antarctic, and 7 other mars meteorites for a ratio of 39:36:25 vs the ratio above of 20:70:10. It would be interesting to see how the other rare meteorite types compare. Bernd? I don't know those comparisons but would guess the results would be closer to the mars ratios than the named classification ratio. Another comparison would be total mass. We know that NWA 869 has been estimated at 1500-2000kg alone. What is the mass of all the antartic meteorites?
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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