Deuterium on Mars: The Abundance of HDO and the Value of D/H.

Deuterium on Mars has been detected by the resolution of several Doppler-shifted lines ofHDO near 3.7 micrometers in the planet's spectrum. The ratio of deuterium to hydrogen is (9 +/- 4) x 10(-4); the abundance of H(2)0 was derived from lines near 1.1 micrometers. This ratio is enriched on Mars over the teiluric value by a factor of6 +/- 3. The enrichment implies that hydrogen escaped more rapidly from Mars in the past than it does now, consistent with a dense and warm ancient atmosphere on the planet.