Fabian Weichbold, IWF, Graz

Venus’ D/H ratio as a tracer of atmospheric escape and planetary evolution

The present-day deuterium-to-hydrogen (D/H) ratio in Venus’ atmosphere is enriched by approximately a factor of 120 relative to Earth, providing important evidence for substantial water loss throughout the planet’s history. However, the timing and extent of this loss, and its implications for Venus’ past habitability, remain uncertain. Observations from the SPICAV instrument aboard Venus Express indicate an increase in D/H with altitude, suggesting that hydrogen and deuterium may undergo different escape processes in the upper atmosphere.

Measurements of proton and deuterium pick-up ion cyclotron waves from Venus Express provide altitude-dependent constraints on the isotopic composition of Venus’ extended exosphere. The inferred escape rates indicate lower hydrogen but higher deuterium loss than previously anticipated, supporting a scenario in which a substantial fraction of Venus’ water was lost early in its evolution. These findings have implications for proposed scenarios involving prolonged habitable conditions or a comparatively recent liquid-water ocean. Online presentation

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