A Martian Crustal Component of Nitrogen and Noble Gases in Mil

Introduction: Martian meteorite studies have provided information on the composition of noble gases and nitrogen in the atmosphere and interior of planet Mars [1]. Two interior components (Chass-S, Chass-E) in Chassigny [2,3]; a mixture of interior (Chass-S) and modern Mars atmosphere in Shergottites [4], elementally fractionated atmosphere in Nakhlites [5] and ancient Mars atmosphere in ALH84001 [6] have so far been identified. Contamination from elementally fractionated terrestrial atmosphere , particularly in martian meteorites from hot deserts pose a serious problem in identifying genuine martian components [7]. Here we discuss N, Ar and Xe data from falls and/or Antarctic finds to evaluate the martian interior components. Nakhla, Y000593 and MIL03346 have been studied for noble gases and nitrogen by vacuum crushing (VC) and/or step-wise pyrolysis (P) and some of the data have been reported earlier [8]. The low temperature releases are the focus of discussion here. Results: The low temperature (up to 400 o C) steps of two bulk samples of Nakhla (NK-30, NK-34) released N (26%, 41%) with δ 15 N of ~20‰, 36 Ar (2.3%, 6.5%) with 40 Ar/ 36 Ar ~ 3000 and negligible amounts of Kr and Xe. The Mars atmospheric component in Y000593 is very minor [8], making it a good candidate to look for interior components. The gases released in VC account for <3% N, with δ 15 N(-12.5‰), while the low T (300-400 o C) steps account for 55% N, 46% Ar and 69% Xe with δ 15 N(25‰), (40 Ar/ 36 Ar = 181) and (129 Xe/ 132 Xe) = 1.039. This low T release is a clear interior component, similar to Chass-E [3], except for heavier δ 15 N. For MIL 03346 the low T (upto 400 o C) release accounts for 85% of N (+30‰) and is accompanied by only ≤10% of Ar, Kr, Xe having 129 Xe/ 132 Xe = 1.989, 136 Xe/ 132 Xe = 0.3695 and 40 Ar/ 36 Ar = 135000. This component is distinct from the low T release of Y000593. The ratio 129 Xe r / 136 Xe f = 12.7 is distinct from that observed in Nakhla (~6) and the Mars modern atmosphere, as observed in Shergottites [1]. Discussion: The composition of gases released at low T in the three nakhlites are different and can not be explained either as terrestrial contamination or as a mixture of earlier identified components. The low T component …