Date: Monday 22-Mar-2021
Time: 11:15-12:15
Location: Zoom
Speaker: Maggie Thompson (UCSC)
Title: Terrestrial Planet Atmospheres: Their Outgassing Origins and Potential Biosignatures
The next phase of exoplanet science will focus on characterizing exoplanet atmospheres, including those of low-mass, terrestrial planets. In this talk, I will discuss two ongoing projects that seek to better understand the origins of and potential biosignatures in terrestrial exoplanet atmospheres.
The first project is motivated by the fact that, at present, there is no first-principles understanding of how to connect a planet’s bulk composition to its initial atmospheric properties. Since terrestrial exoplanets likely form their atmospheres through outgassing, a novel step towards building such a theory is to assay meteorites, the left-over building blocks of planets, by heating them to measure their outgassed volatiles. Our Solar System presents a wide variety of meteorite types, including carbonaceous chondrites which are believed to be representative of the bulk material in the solar nebula during planet formation. To inform the initial chemical composition of terrestrial planet atmospheres, I will present the results of outgassing experiments in which we heated carbonaceous chondrite samples to 1200 ℃ and measured the abundances of released volatiles (e.g., H2O, CO, CO2, H2, H2S) as a function of temperature and time. We also performed complementary bulk element analysis on the samples before and after the heating experiments to monitor outgassing of heavier elements (e.g., Mg, P, S, Ca, Mn, Fe). I will discuss how these experimental results compare to thermochemical equilibrium models of outgassing from the same types of chondrites and how these experiments can help improve atmospheric models.
The second project focuses on methane, a potential biosignature gas for terrestrial exoplanet atmospheres. As we move into the era of JWST and ELTs, a comprehensive understanding of possible biosignatures that may be detected with the next generation of ground and space telescopes is warranted. While some biosignature gases, such as oxygen and phosphine, have recently been reviewed in depth, these will likely be extremely difficult to detect with JWST. In contrast, while it has not been thoroughly reviewed, methane at Earth-like biogenic fluxes is one of the only biosignatures that may be readily detectable with available near-term instruments. I will present our preliminary work on a comprehensive review of methane biosignatures and false positives.
For further information contact PALS coordinator Dr. Lori Feaga at feaga@astro.umd.edu or (301)-405-1383.
SPECIAL ACCOMMODATIONS:Special accommodations for individuals with disabilities can be made by calling (301) 405-3001. It would be appreciated if we are notified at least one week in advance.
