Stable isotopic measurements of the low-temperature nitrogen components inALH 84001

The distribution and stable isotopic composition of nitrogen released at lo w temperatures from the ALH 84001 Martian meteorite have been appraised. Th e results demonstrate an apparently complex geochemistry of the element, wi th at least three, and possibly four, separate components present. While th e isotopic composition of most of the nitrogen is within the range of typic al terrestrial materials (and thus is probably contamination), nitrogen in the balance of the material has a very different delta(15)N value. Isotopic ally light nitrogen (component N2; 2.2 ppm with delta(15)N similar to -30 p arts per thousand and C/N similar to 6) is released when a carbonaceous pha se combusts below 300 degrees C. Since amino acids and nucleic acid bases h ave C/N similar to 2-3, the host phase of N2 could be from a mixture of suc h compounds. The associated nitrogen isotopic composition is very different from terrestrial contaminants; while this is suggestive of a Martian origi n for the components, it is difficult to reconcile without advocating forma tion under special conditions.