Special EPS Colloquium

Date: 

Tuesday, February 16, 2021, 3:00pm

Location: 

Zoom

Presenting: Robin Wordsworth, Associate Professor of Environmental Science and Engineering, Harvard University

Title: The Role of Water in Planetary Habitability

Abstract: The status of liquid water as essential to all known life ensures it plays a central role in modern definitions of habitability. However, the relationship between water and planetary habitability is far more subtle than is often assumed. Here I discuss some of the ways in which water affects the evolution of terrestrial-type planets. For Mars, I discuss how episodic warming once created abundant liquid water at the surface, but the slow conversion of water to highly oxidizing compounds via hydrogen escape has rendered the surface inhospitable to life today. Extensive water loss from terrestrial-type exoplanets around red dwarf stars (the only kind that will be amenable to atmospheric characterization in the next decade) has probably also left many of them oxidized and with only residual water frozen as ice in cold traps. However, some of those that retain atmospheres may still possess dayside surface liquid water via efficient tropospheric cold-trapping at the sub-stellar point. Detecting surface water and/or biosignatures on these planets will be challenging, although the sulfur cycle provides a novel way to place important constraints. An immense opportunity exists over the coming decade to probe these intricate links between water, redox and planetary habitability further, via a combination of in situ investigations by the Perseverance rover and characterization of rocky exoplanets by James Webb and the next generation of ground-based telescopes.