The origin of organic matter in the Martian meteorite ALH84001

Stable carbon isotope measurements of the organic matter associated with the carbonate globules and the bulk matrix material in the ALH84001 Martian meteorite indicate that two distinct sources are present in the sample. The delta(13)C values for the organic matter associated with the carbonate globules averaged -26 parts per thousand and is attributed to terrestrial contamination, In contrast, the delta(13)C values for the organic matter associated with the bulk matrix material yielded a value of -15 parts per thousand. The only common sources of carbon on the Earth that yield similar delta(13)C values, other then some diagenetically altered marine carbonates, are C(4) plants. A delta(13)C value of -15 parts per thousand, on the other hand, is consistent with a kerogen-like component, the most ubiquitous form of organic matter found in carbonaceous chondrites such as the Murchison meteorite. Examination of the carbonate globules and bulk matrix material using laser desorption mass spectrometry (LDMS) indicates the presence of a high molecular weight organic component which appears to be extraterrestrial in origin, possibly derived from the exogenous delivery of meteoritic or cometary debris to the surface of Mars. (C) 1999 Published by Elsevier Science B.V. All rights reserved.