Signatures of the Martian Atmosphere in Glass of the Zagami Meteorite

Abstract

Isotopic signatures of nitrogen, argon, and xenon have been determined in separated millimeter-sized pockets of shock-melted glass in a recently identified lithology of the meteorite Zagami, a shergottite. The ratio of nitrogen-15 to nitrogen-14, which is at least 282 per mil larger than the terrestrial value, the ratio of xenon-129 to xenon-132 = 2.40, and the argon isotopic abundances match the signatures previously observed in the glassy lithology of the Antarctic shergottite EETA 79001. These results show that the signatures in EETA 79001 are not unique but characterize the trapped gas component in shock-melted glass of shergottites. The isotopic and elemental ratios of nitrogen, argon, and xenon closely resemble the Viking spacecraft data for the martian atmosphere and provide compelling evidence for a martian origin of the two shergottites and, by extension, of the meteorites in the shergottites-nakhlites-chassignites (SNC) group.

Noble gases in mineral separates from three shergottites: Shergotty, Zagami, and EETA79001

“…Their findings were confirmed on the same meteorite by Becker and Pepin (1984a). Martian atmosphere was also later shown to be present in shock glasses of Zagami (Marti et al 1995) and Shergotty .…”

Noble gases and nitrogen in Tissint reveal the composition of the Mars atmosphere

“…Some of these (e.g., EETA 79001, Zagami, ALH84001, Tissint, NWA 7034) contain glassy melt pockets or veins created during impacts on Mars that ejected fragments of Martian crust into space (Becker and Pepin, 1984;Marti et al, 1995;Murty and Mohapatra, 1997;Bogard and Garrison, 1998;Chennaoui Aoudjehane et al, 2012;Cartwright et al, 2014). Melt pockets present noble gases and nitrogen compositions (e.g., Becker and Pepin, 1984;Wiens et al, 1986) comparable to those measured on Mars by the Viking lander (Owen et al, 1977), strongly supporting their Martian origin (Treiman et al, 2000).…”

39Ar‐40Ar “ages” and origin of excess 40Ar in Martian shergottites

“…(NWA 3171 melt, containing Martian atmosphere, is not plotted here, but is plotted in Fig. 16 (Garrison and Bogard 1998), NWA 3171 (glass sample, this work), and Zagami (Marti et al 1995).…”