16 October, 2002
Although this is not a normal part of the TEA experience, I'm not sure what would define a "normal" part. Right now, I'm experiencing a "round the horn" trip around the country visiting members of my research team and learning what kind of research they do. The first part of the trip brought me to Washington, D.C., where I visited the meteorite staff and collection at the National Museum of Natural History. Next, I'll visit with the staff at the Johnson Space Center in Houston, TX.
I'm actually tracing the path of a meteorite on its journey from Antarctica to the scientist...only backwards. The Smithsonian is actually one of the last stops for a meteorite. The meteorite curator, Dr. Tim McCoy, greeted me first and immediately showed me some of the most spectacular meteorites in the collection. He quizzed me about my knowledge of meteorites and let me hold some of his treasures. I actually got to hold a couple of pieces of Mars. One meteorite, called Nakhla, is famous for not only coming from Mars, but is also credited with killing a dog in Egypt where it fell in 1911. There is very little evidence to support this story (unless you're the dog).
The other piece I held doesn't have a name, but rather an alphanumerical designation, as do all Antarctic meteorites. It's called ALH84001 and was in the news a few years ago because researchers claimed to have found the fossil traces of life in it. The process of science is one of continuous change and chances are that life did not occur in this rock, but it raised some interesting questions about where and how life began.
When meteorites reach the Smithsonian, they are quickly clipped and ground into a powder. A technician like Gretchen puts a drop of oil on the grains and looks at them under a petrographic microscope. When turned at an orientation that causes the crystals to disappear under cross-polarized light, Gretchen removes the cross-polars and adjusts the focus to see which way shadow-like lines (called Beckey lines) move. That tells her what kind of a meteorite it is. Gretchen has done this so many that she can usually tell before even applying the oil, but still must be absolutely certain.
The Smithsonian keeps a file of thin sections and all the fragments of the meteorites they classify. Twice a year, a publication goes out discussing the characteristics of each of the meteorites examined. Scientists then can request specific samples on which to conduct their research. The Smithsonian contains some of the most impressive samples I've ever seen.
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