Water On -and In- Terrestrial Planets

TL;DR

This paper argues that Earth's bimodal surface, with continents and oceans, is crucial for climate stability and habitability, and discusses how future missions can determine exoplanet surface types.

Contribution

It highlights the importance of Earth's surface bimodality for habitability and proposes methods to identify surface features on exoplanets with upcoming space missions.

Findings

Earth's bimodal surface contributes to climate stability.

Next-generation missions can distinguish exoplanet surface types.

Surface character is a key habitability indicator.

Abstract

Earth has a unique surface character among Solar System worlds. Not only does it harbor liquid water, but also large continents. An exoplanet with a similar appearance would remind us of home, but it is not obvious whether such a planet is more likely to bear life than an entirely ocean-covered waterworld---after all, surface liquid water defines the canonical habitable zone. In this proceeding, I argue that 1) Earth's bimodal surface character is critical to its long-term climate stability and hence is a signpost of habitability, and 2) we will be able to constrain the surface character of terrestrial exoplanets with next-generation space missions.