Moderate D/H Ratio for a Surficial Water Reservoir on Mars.

摘要

Martian surface morphology implies that Mars was once warm enough to maintain persistent liquid water on its surface and that water played a significant role in the formation of weathered/altered terrains (e.g., 1, 2, 3). Volatiles exhaled by volcanic activity would have been the dominant greenhouse gases and would have significantly affected the Martian climate. The enrichment of some volatile elements in the atmosphere, which would have dissolved in surface water, could also have influenced water chemistry (e.g., acidity) and played a significant role in weathering and aqueous alteration processes. While much of this picture is qualitative, Martian meteorites contain records of major Martian volatile reservoirs. This study characterizes Martian surficial volatile reservoirs based on in situ ion microprobe analyses of volatile abundances and H-isotopes of glassy phases (groundmass glass (GG) and impact melt (IM)) in Martian basalts (shergottites). Although these meteorites are of igneous origin, some glassy phases underwent impact-induced modification that trapped surficial and atmospheric volatile components (4, 5); e.g., inert gases contained in IMs from EETA79001 (EETA79) match the relative abundances of modern Martian atmosphere (6). Analyses of these glassy phases demonstrate that surficial volatile reservoirs have distinct D/H ratios from their magmatic volatiles.