NITROGEN AND NOBLE-GASES IN A GLASS SAMPLE FROM THE LEW88516 SHERGOTTITE

A glass separate from the LEW88516 shergottite was analyzed by step-wi se combustion for N and noble gases to determine whether it contained trapped gas similar in composition to the martian atmosphere-like comp onent previously observed in lithology C of EETA79001. Excesses of Ar- 40 and Xe-129 were in fact observed in this glass, although the amount s of these excesses are less-than-or-equal-to 20% of those seen in the latter meteorite, and are comparable to the amounts seen in whole-roc k analyses of LEW88516. The isotopic composition of N in LEW88516 does not show an enrichment in deltaN-15 commensurate with the amount of i sotopically-heavy N expected from the noble gases excesses. One must p osit some extreme assumptions about the nature of the N components pre sent in LEW88516 in order to allow the presence of the trapped nitroge n component. Alternatively, the N has somehow been decoupled from the noble gases, and was either never present or has been lost.