Venus as a Laboratory for Exoplanetary Science

TL;DR

Venus serves as a natural laboratory to understand the processes that lead to uninhabitable conditions on planets, aiding the search for biosignatures and characterization of exoplanets through remote sensing and comparative analysis.

Contribution

This paper reviews current knowledge of Venus, discusses its relevance as an analog for exoplanets, and outlines future research directions in exoplanetary science and habitability.

Findings

Venus exemplifies a completely uninhabitable environment.

Venus analogs are identified in exoplanet surveys like Kepler and TESS.

Understanding Venus helps define habitable zone boundaries and exoplanet atmospheres.

Abstract

The current goals of the astrobiology community are focused on developing a framework for the detection of biosignatures, or evidence thereof, on objects inside and outside of our solar system. A fundamental aspect of understanding the limits of habitable environments (surface liquid water) and detectable signatures thereof is the study of where the boundaries of such environments can occur. Such studies provide the basis for understanding how a once inhabitable planet might come to be uninhabitable. The archetype of such a planet is arguably Earth's sibling planet, Venus. Given the need to define the conditions that can rule out biorelated signatures of exoplanets, Venus provides a unique opportunity to explore the processes that led to a completely uninhabitable environment by our current definition of the term. Here we review the current state of knowledge regarding Venus, particularly in the context of remote sensing techniques that are being or will be employed in the search for and characterization of exoplanets. We discuss candidate Venus analogs identified by the Kepler and TESS exoplanet missions and provide an update to exoplanet demographics that can be placed in the potential runaway greenhouse regime where Venus analogs are thought to reside. We list several major outstanding questions regarding the Venus environment and the relevance of those questions to understanding the atmospheres and interior structure of exoplanets. Finally, we outline the path towards a deeper analysis of our sibling planet and the synergy to exoplanetary science.