Venusian Habitable Climate Scenarios: Modeling Venus through time and
applications to slowly rotating Venus-Like Exoplanets
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. 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. Venus’ long lived steam atmosphere would
sufficient time to dissociate most of the water vapor, allow significant
hydrogen escape and oxidize the magma ocean. A third scenario is that
Venus had surface water and habitable conditions early in its history
for a short period of time (<1 Gyr), but that a moist/runaway
greenhouse took effect because of a gradually warming sun, leaving the
planet desiccated ever since. Using a general circulation model we
demonstrate the viability of the first scenario using the few
observational constraints available. We further speculate that Large
Igneous Provinces and the global resurfacing 100s of millions of years
ago played key roles in ending the clement period in its history and
presenting the Venus we see today. 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.”