May 17, 2024

The ExoExplorer Science Series presents talks by cohort members Galen Bergsten (U Arizona) & Michaela Leung (UC Riverside) on May 17, 2024, from 11 AM - 12 PM Pacific Standard / 2 PM - 3 PM Eastern Standard. Connection information is below.

Speaker: Galen Bergsten (U Arizona)

Title: Demographics of Earth-sized Planets in the Habitable Zone, from Kepler to the Habitable Worlds

Abstract: The frequency of Earth-sized planets in the habitable zone is a key parameter in the design and success of future missions like the Habitable Worlds Observatory. Yet our estimates – and the Kepler sample that many are based on – are subject to change, as we learn more about the physical and statistical processes affecting planetary populations and our ability to study them. In this talk, I’ll introduce two recent investigations of Kepler’s Earth-sized planets, alongside ongoing efforts to expand our view beyond single-star, single-survey studies. In the first portion, I’ll describe how a population-level trend in atmospheric evolution helped identify the primordially rocky population of Earth-sized planets around Sun-like stars. In the second portion, I’ll explore how a decade of innovation has reshaped our understanding of Kepler’s M dwarfs and their Earth-sized planets. In both segments, I’ll provide our best estimates for the frequency of Earth-sized planets in the habitable zone, and their implications for the Habitable Worlds Observatory. Finally, I’ll discuss ongoing efforts to address open questions on this topic, like how we can move past Kepler’s limitations, and how our occurrence estimates are sensitive to Kepler’s unresolved stellar companions.

Speaker: Michaela Leung (UC Riverside)

Title: Methylated Gases: A Class of Exoplanet Biosignatures

Abstract: In the JWST era and beyond, the search for signs of life on exoplanets is entering a new era where detection of atmospheric biosignatures may soon be possible. To maximize the application of this exciting opportunity, it is essential to identify many potential biosignatures and their specific environmental applicability. Many biosignature candidates, such as O2 and CH4, have significant potential false positives generated by abiotic processes. To address this issue, we propose the use of methylated gases as “capstone biosignatures”. The process of biomethylation, often an environmental detoxification mechanism, can utilize and subsequently volatilize a broad range of substrates including halogens, chalcogens, and metalloids (eg CH3Cl, CH3Br, CHBr3, CH3I, DMS, etc). Methylated gases are not produced as equilibrium products and have extremely limited pathways for abiotic production; therefore, they are signs of life with low ambiguity. Here we present simulations of flux-abundance relationships for a variety of methylated halogen gases such as CH3Cl, CH3I and CHBr3. Self-consistent simulations reveal that the presence of multiple methylated gases enhances individual buildup levels and lowers the threshold for photochemical runaway, increasing the potential detectability of methylated gas features and their application as remote biosignatures.

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Meeting ID: 895 6518 0020