A dry Venusian interior constrained by atmospheric chemistry

TL;DR

This study constrains Venus's climate history by analyzing atmospheric destruction rates and volcanic gases, revealing a dry interior that suggests Venus was never habitable with surface liquid water.

Contribution

The paper introduces a novel method to infer Venus's interior water content from atmospheric and volcanic gas analysis, providing new insights into its climatic past.

Findings

Venus's interior is very dry, with volcanic gases containing at most 6% water.

Venus likely ended its magma ocean epoch desiccated and has remained dry since.

The dry interior supports the idea that Venus was never in a liquid-water habitable state.

Abstract

Venus's climatic history provides powerful constraint on the location of the inner-edge of the liquid-water habitable zone. However, two very different histories of water on Venus have been proposed: one where Venus had a temperate climate for billions of years, with surface liquid water, and the other where a hot early Venus was never able to condense surface liquid water. Here we offer a novel constraint on Venus's climate history by inferring the water content of its interior. By calculating the present rate of atmospheric destruction of H$_2$O, CO$_2$ and OCS, which must be restored by volcanism to maintain atmospheric stability, we show Venus's interior is dry. Venusian volcanic gases have at most a 6% water mole fraction, substantially drier than terrestrial magmas degassed at similar conditions. The dry interior is consistent with Venus ending its magma ocean epoch desiccated and thereafter having had a long-lived dry surface. Volcanic resupply to Venus's atmosphere therefore indicates that the planet has never been `liquid-water' habitable.