Investigation of Venus' thermal history, crustal evolution, and core dynamics with a coupled interior-lithosphere-atmosphere model

TL;DR

This study models Venus' interior and atmospheric evolution to identify plausible histories explaining its current state, including water content, volcanic activity, and magnetic field presence, using coupled simulations and machine learning.

Contribution

It introduces a coupled interior-atmosphere model combined with random forest classification to explore Venus' thermal and geological evolution, revealing multiple plausible pathways.

Findings

Venus likely retains at least one Earth ocean's worth of water in its mantle.

Most plausible histories include a past magnetic field, despite current lack of a dynamo.

Venus is not as volcanically inactive as previously thought.

Abstract

We simulate Venus' evolution with a coupled one-dimensional solar-atmosphere-lithosphere-mantle-core model to predict currently unobservable features and its eruptive mass flux. We identified four distinct evolutionary pathways that simultaneously match the atmospheric abundances of water and carbon dioxide as well as the lack of a core dynamo. These scenarios are characterized by I) generally monotonic cooling, II) a low mantle melt fraction in which Venus' volcanically active phase is ending, III) a small inner core, and IV) oscillations of internal properties. Through random forest classification we determined that the key parameters that distinguish these types are the initial mantle water abundance, the mantle viscosity, the dehydration stiffening strength, the eruption efficiency, and the melting point of the core. In each of the plausible histories, Venus retains at least one Earth ocean's worth of water in its mantle and remains volcanically active today. Venus' lack of a current geodynamo allows thermal histories with an initially large inner core in our parameter sweep. In 88% of plausible histories we found that Venus possessed a past magnetic field. The results strongly disfavor recent high eruption rate estimates, but are consistent with lower estimates. Current resurfacing estimates also strongly disfavor the low melt scenario, implying that Venus is not nearly volcanically ``dead.'' These predictions are testable with anticipated data and the model can be applied to exoplanets to predict their properties.