GEOCHEMISTRY: Mars Piece by Piece

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Science  24 Nov 2000:
Vol. 290, Issue 5496, pp. 1465b
DOI: 10.1126/science.290.5496.1465b

The only direct samples we have of Mars come from 16 Martian meteorites. Several new samples have been found in the past few years, including one discovered, or rather recognized, in late 1999 after having resided in a private collection in Los Angeles for some 20 years.

Rubin et al. now describe the geochemistry of this Los Angeles meteorite which provides new information on the nature of the Martian crust. The meteorite contains a variety of geochemical fingerprints supporting its Martian origin, including its oxygen and hydrogen isotopic values. Compared to the other Martian meteorites, Los Angeles has a low magnesium:iron ratio and a high abundance of certain trace elements indicating that the meteorite is derived from a more chemically evolved magma on Mars. Its composition, like that of the other meteorites, is not a close match to the Martian soil analyses recorded by the Mars Pathfinder. In a separate study, Jull et al. show that another Martian meteorite, Nakhla, contains clear evidence of extraterrestrial organic material. They conclude that the most likely origin of this organic matter is from the accumulation of cometary debris and carbonaceous cosmic dust over time on the Martian surface. — BH

Geology 28, 1011 (2000); Geochim. Cosmochim. Acta 64, 3763 (2000).

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