Strong water isotopic anomalies in the martian atmosphere: Probing current and ancient reservoirs

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Science  05 Mar 2015:
DOI: 10.1126/science.aaa3630

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We measured maps of atmospheric water (H2O) and its deuterated form (HDO) across the martian globe, showing strong isotopic anomalies and a significant high D/H enrichment indicative of great water loss. The maps sample the evolution of sublimation from the north polar cap, revealing that the released water has a representative D/H value enriched by a factor of about 7 relative to Earth’s ocean (VSMOW). Certain basins and orographic depressions show even higher enrichment, while high altitude regions show much lower values (1 to 3 VSMOW). Our atmospheric maps indicate that water ice in the polar reservoirs is enriched in deuterium to at least 8 VSMOW, which would mean that early Mars (4.5 billion years ago) had a global equivalent water layer at least 137 meters deep.

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