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Venusian Habitable Climate Scenarios: Modeling Venus through time and applications to slowly rotating Venus-Like Exoplanets
  • Michael Way,
  • Anthony D. Del Genio
Michael Way
NASA/Goddard Institute for Space Studies, NASA/Goddard Institute for Space Studies, NASA/Goddard Institute for Space Studies

Corresponding Author:[email protected]

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Anthony D. Del Genio
National Aeronautics and Space Administration (NASA), National Aeronautics and Space Administration (NASA), National Aeronautics and Space Administration (NASA)
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Abstract

One popular view of Venus’ climate history describes a world that has spent much of its life with surface liquid water, plate tectonics, and a stable temperate climate. This leads to the conclusion that Venus’ present state is the result of a runaway greenhouse from a gradually warming sun since its formation. Part of the basis for this optimistic scenario is the high deuterium to hydrogen ratio from the Pioneer Venus mission that was interpreted to imply Venus had a shallow ocean’s worth of water throughout much of its history. Another view is that Venus had a long lived (~100 million year) primordial magma ocean with a CO2 and steam atmosphere because of its closer proximity to the Sun. This would differ from Earth’s evolution since Earth’s magma ocean lifetime was probably around 1 million years. Venus’ long lived steam atmosphere would allow sufficient time to dissociate most of the water vapor, allow significant hydrogen escape and oxidize the magma ocean. Maybe the high deuterium to hydrogen ratio is from this period. However, a dearth of observational data due to a lack of missions to Venus makes it impossible to choose between these two scenarios. Using a general circulation model we demonstrate the viability of the optimistic scenario using the few observational constraints available. The results have implications for what astronomers term “the habitable zone,” and if Venus-like exoplanets exist with clement conditions akin to modern Earth we propose to place them in what we term the “optimistic Venus zone.”
May 2020Published in Journal of Geophysical Research: Planets volume 125 issue 5. 10.1029/2019JE006276