Years after a small meteorite called ALH84001 found in the snow of Antarctica was discovered to be from Mars, further investigation of chemical tests performed on the rock began to indicate possible evidence for life. That began to convince some scientists.
Ten years after the rock was found in 1984, David Mittlefehldt, a geochemist at Lockheed-Martin, found that the rock had been misclassified as a diogenite. Oxygen in the rock tipped him off that it was not a diogenite. Diogenites are not supposed to have oxygen in them, but this one did.
It was a meteorite from Mars. Gases in the rock matched exactly with the samples from the Viking spacecraft, an automated biology laboratory which landed on Mars in 1976. There are only eleven other meteorites from Mars, but none as special as this one. This one is from Mars's crust, the surface of Mars, and might prove there is some type of life on Mars.
Using an electron microscope to examine the meteorite, David McKay found a segmented structure that appeared to have a tail and a head and was fat in the middle. This seemed to indicate biogenic activity. Mrs. Thomas-Kapurta thought that the theory of fossilized life in the meteorite was farfetched. She used a transmission electron microscope five to ten times more powerful than McKay's. She described the carbonate globular structures as having an amber color in the center with black and white rims. She found coexisting minerals in the rings which don't normally appear together. She found iron and oxygen grains (magnetides) and iron and sulphur grains that are similar to what bacteria produce on Earth.
Photo. ALH84001, close up. Courtesy of NASA.
Hydrocarbons are a part of past life like dinosaur fossils. McKay wanted to look for hydrocarbons in the meteorite and called on Stanford University for help. The samples, with nicknames of characters from Disney movies, were turned over to the chemistry department. McKay didn't want to say much about the samples because it might influence the researchers' objectivity if they knew in advance what he suspected.
Chemistry professor Richard Zare used a dual-laser mass spectrometer, the most sensitive molecule detector on Earth. When Zare tested the meteorite, he found polycyclic aromatic hydrocarbons (PAHs). These can be found in some types of exhaust fumes, but the fact that they were found underneath the surface of the meteorite ruled out the possibility of terrestrial contamination.
Photo. ALH84001, close up. Courtesy of NASA.
After two years of collecting evidence, Johnson Space Center scientists were ready to write up a report and break the secrecy. They were secretive because the press jumps on anything about Mars, especially the topic life on Mars. Everything in the press about Mars is sensationalized.
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