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Dix Planetary Science Seminar

Tuesday, February 26, 2019
4:00pm to 5:00pm
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South Mudd 365
Stable Isotopes as a Window into the Processes and History of Climate on Mars
Renyu Hu, Hubble Fellow, Jet Propulsion Laboratory,

How the climate of Mars has evolved over time to reach its current state is a fundamental question that underpins the Solar System exploration. Motivated by recent isotopic data, I devise a million-model approach to determine the plausible evolution pathways of the Martian atmosphere, combining atmospheric escape, volcanic outgassing, and deposition to the surface as alteration minerals and salts. In particular, the photochemical escape of carbon and nitrogen is found to efficiently fractionate the gases that remain in the atmosphere, and this Photochemical Isotope Effect (PIE) implies a limited amount of escape of CO2 and N2 for the observed isotopic enrichment. Furthermore, interpretation of the hydrogen isotopes must be based upon understanding the water cycle on present-day Mars. I develop a new model to determine the isotope effect due to regolith-atmosphere exchange of water, and find that D can vary by 300 – 1400‰ diurnally from equatorial to polar locations. The regolith reservoir of water has distinct isotopic signatures from those in the atmosphere, and it can drive substantial seasonal variation in agreement with recent observations. I will conclude with a prospect of how stable isotope analysis can be a powerful tool to pinpoint the climate of Mars from the present day to the ancient past, as well as the evolution of other bodies in the Solar System.