Mars as a case study of an intermittently habitable planet
Robin Wordsworth
Harvard University

The planet Mars has engaged the curiosity of scientists and amateurs alike for centuries, but many aspects of its evolution remain poorly understood. In particular, Mars contains abundant evidence for erosion by liquid water 3-4 Ga, but due to the faintness of the young Sun, basic climate theory suggests its surface should have been extremely cold. Here I describe our recent progress on this important planetary science problem. Based on 3D climate model results, I describe how adiabatic cooling under a thicker CO2 atmosphere would have led to stabilization of snow and ice deposits in the highland regions where most surface aqueous alteration is recorded. I then show that bursts of me-thane and hydrogen outgassed into this atmosphere, via mechanisms analogous to those that occur on Titan, would have led to intense intermittent warming on moderate (~100,000 y) timescales. This scenario fits many aspects of the geologic record and will be amenable to further in-situ testing by the Mars 2020 rover. Finally, I discuss the importance of Mars as a case study for planetary evolution in general, and argue that comparative planetology can lead us to new insights on exoplanet habitability and biosignatures.

Date:	Mardi, le 25 septembre 2018
Heure:	15:30
Lieu:	Université McGill
	McGill Space Institute (3550 University), Conference Room