Was Venus the First Habitable World of our Solar System?

TL;DR

This study uses 3D climate simulations to explore whether early Venus could have been habitable, highlighting the importance of rotation period and topography in planetary climate evolution.

Contribution

The paper introduces a novel 3D climate modeling approach to assess early Venus's habitability considering different rotation periods and topography.

Findings

Venus could have been habitable with a rotation period slower than 16 days.

Habitable conditions might have persisted until 715 million years ago at current rotation.

Rotation and topography significantly influence exoplanetary climate and habitability.

Abstract

Present-day Venus is an inhospitable place with surface temperatures approaching 750K and an atmosphere over 90 times as thick as present day Earth's. Billions of years ago the picture may have been very different. We have created a suite of 3D climate simulations using topographic data from the Magellan mission, solar spectral irradiance estimates for 2.9 and 0.715 billion years ago, present day Venus orbital parameters, an ocean volume consistent with current theory and measurements, and an atmospheric composition estimated for early Venus. Using these parameters we find that such a world could have had moderate temperatures if Venus had a rotation period slower than about 16 Earth days, despite an incident solar flux 46-70% higher than modern Earth receives. At its current rotation period of 243 days, Venus's climate could have remained habitable until at least 715 million years ago if it hosted a shallow primordial ocean. These results demonstrate the vital role that rotation and topography play in understanding the climatic history of exoplanetary Venus-like worlds being discovered in the present epoch.