An Ozone Layer on Early Mars? Leveraging Techniques from Earth Science to Understand Habitability at the Red Planet

forthcoming

For decades, Mars exploration has focused on evidence for life to answer the fundamental question: Are we alone in the universe? I will investigate the possibility of life on early Mars by leveraging decades of research on Earth’s atmosphere to understand that of the red planet. I will use a well-established photochemical model constrained by observations from complementary missions to explore whether ancient Mars ever had a protective ozone layer that could have shielded surface-dwelling life. The ozone layer is critical on Earth, securing surface habitability from DNA-damaging UV radiation and controlling the temperature structure of the middle atmosphere, with important climatic effects. Our understanding of how Earth’s ozone levels have changed has quickly expanded in recent decades. Here, I will apply lessons learned from Earth to the evolution of a second system—Mars—which will provide unique insights into factors that control planetary atmospheres and the search for life in the universe. Specifically, I will investigate the utility of ratios of the three oxygen isotopes, used extensively to understand oxidative chemistry and atmospheric composition changes on Earth, to constrain Mars ozone densities through the following three objectives. I will: 1) predict triple oxygen isotope signatures for the present-day Mars atmosphere and compare to observations, to better understand controls on isotope composition; 2) determine realistic palaeo-atmospheric conditions conducive to an ozone layer; and 3) predict the oxygen isotope composition of select geological materials for potential early Mars conditions and prioritise options for future exploration. We are in the midst of a revolutionary accumulation of spacecraft data and unprecedented Mars exploration, making this work perfectly timed. Preparation for interpretation of measurements from Mars via my proposed modelling is critical to focus future observational efforts from space agencies globally.