Mars Climate and Chemical Evolution: Lessons from the Solar System for Exoplanets HD

April 4, 2019 Phillips Auditorium Robin Wordsworth Harvard, SEAS Host: Karin Öberg Abstract: The current era of planetary atmospheric research is characterized by a divide between the solar system, where data is rich but the number of objects to be studied is small, and exoplanets, where data is sparse but the full range of possible states is extremely large. Paleoclimate research is an essential tool with which to bridge this gap, because it allows us to see the present-day surface environments of Earth, Mars and Venus as mere snapshots of nonlinear systems that have evolved significantly over time. Here, I focus on Mars as a case study to show how this approach can yield important insights in practice. Mars has abundant evidence for intermittent habitable conditions in its first gigayear of evolution, but the theoretical explanation for this evidence is a long-standing problem in the field. I discuss how detailed intercomparisons between 3D climate models and the geological evidence have allowed us to gain new insights into the nature of the early Martian hydrological cycle. In addition, new spectroscopic and radiative calculations show that episodic release of reducing gases (H2 and CH4) into Mars’ early atmosphere could have caused intense intermittent warming, potentially resolving the decades-old faint young Sun problem. Based on these insights into Mars’ climate and redox history, we are now developing a greater understanding of exoplanet atmospheric evolution, including the critical question of when gases like oxygen (O2) can be treated as biosignatures.