Was Venus Wet? Deuterium Reconsidered

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Science  18 Dec 1987:
Vol. 238, Issue 4834, pp. 1702-1704
DOI: 10.1126/science.238.4834.1702


The ratio of deuterium to hydrogen on Venus has been accepted as proof of a wetter, more Earth-like past on that planet. However, the present-day water abundance and the nonthermal hydrogen escape flux on Venus imply that hydrogen is in a steady state and that a hydrogen source, most likely cometary infall, is present. An alternative interpretation of the D/H ratio is offered, in which the measured value is consistent with a steady-state evolution over the age of the solar system. No past water excess is required to explain the isotopic data.