Building a framework for robust biosignature identification on rocky exoplanets

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For the first time in human history, we are reaching the technological capability to detect biosignatures in the atmosphere of an exoplanet. This question of whether biology is unique to Earth lies at the intersection of astronomy, biology, geology and chemistry. My research program will drive forward understanding in three key areas to aid the remote detection of biosignatures on an exoplanet: 1) the impact of of a stars high energy radiation and activity, 2) how clouds affect observations and habitability, and 3) exploring false positive biosignature generation and disambiguation. All these areas centre around one overarching theme: how can we robustly distinguish life from non-life, light years away? One key target of my research program is to better understand the star-planet connection. The most exciting habitable exoplanet targets orbit flare stars, such as our nearest star, Proxima Centauri. However, we do not understand how flares impact atmospheres and our observations. Furthermore, for transiting habitable planets, the James Webb Space Telescope launching in December 2021 will need to add years of observations of separate transits to build up the signal required to detect atmospheric features, and we are unsure if there is variability in atmospheric features on those timescales. My research program will address this. A second area my group will work on is the impact of clouds on exoplanet atmosphere characterisation. Clouds are known to confound current exoplanet observations. Using 1D and 3D modelling tools, my group will learn more about clouds in different atmospheres and under different stellar radiation environments to better understand future exoplanet observations. The third area my program will explore is how to vet future biosignature claims. How robust a biosignature detection is requires an understanding of potential false positive mechanisms. There are several known false positive mechanisms for oxygen, the iconic biosignature, but we still don't know how atmospheric escape maybe linked with photochemistry. Nor has the influence of atmospheric pressure been looked at regarding a double gas biosignature false positive, particularly around flaring or UV active stars. My group will help establish ways for distinguishing known false positives from true biosignature detections. My research program is novel for two reasons - one is that we will tackle questions especially relevant for interpreting the first terrestrial exoplanet observations with JWST and address potential degenerate solutions. This work is designed to answer fundamental questions to understanding future biosignature detections and to capitalize on opportunities arising from JWST and other future missions. Two, my research program is also highly multidisciplinary. It links stellar astrophysics, exoplanet atmospheric modelling, climate, and geobiology. And hopefully, it will bring us closer to answering the age old question of "Are we alone in the Universe?"