Maggie A. Thompson

General Research Interests:

• Rocky exoplanets and their interior-atmosphere connections

• Experimental cosmochemistry & meteoritics

• Astrobiology and the search for life beyond Earth

• Intersection between theoretical, experimental, and observational astronomy and planetary science

• Earth’s atmosphere and mantle evolution through time

UC Santa Cruz (2017-2023)

Understanding Terrestrial Exoplanets’ Initial Atmospheres via Meteorite Outgassing Experiments

• A central part of my Ph.D. thesis used experimental cosmochemistry to understand the early atmospheres of terrestrial exoplanets. At present, there is no first-principles understanding of the link between a planet’s bulk composition and it’s atmospheric properties. Low-mass, rocky planets form their atmospheres via outgassing during accretion (i.e., secondary atmospheres). Therefore, a logical first step towards building such a theory for terrestrial exoplanets is to assay meteorites, the leftover building blocks of planets, by heating them to measure the outgassed volatiles. Our Solar System presents a wide variety of meteorite types, including chondrites which are primitive unaltered rocks believed to be representative of the material that formed the rocky planets. To inform the initial chemical composition of terrestrial planet atmospheres, I performed outgassing experiments in which I heated chondritic meteorite samples to 1200 ℃ and measured the abundances of released volatiles as a function of temperature to which the samples were heated. These experimentally-determined outgassed volatile abundances from various chondrite samples informed the initial boundary conditions that we set in terrestrial exoplanet atmosphere models.

• Our first paper on this work, in which we heated three CM carbonaceous chondrite samples and measured their outgassing compositions, was published in Nature Astronomy (Thompson et al. 2021).

• We also performed heating experiments and bulk element analyses using inductively-coupled plasma mass spectrometry (ICP-MS) on samples of the Murchison meteorite. These experiments monitored outgassing of heavier elements that were not measured during our first set of experiments (e.g., Na, Mg, Fe, Zn, S, Cr, Mn). The paper describing these results is published in The Planetary Science Journal (Thompson et al. 2023).

The Case for Methane as an Exoplanet Biosignature Gas

• The second major component of my Ph.D. thesis consisted of modeling work to determine the necessary planetary and astrophysical conditions for methane to be a compelling biosignature gas. At Earth-like biogenic fluxes, atmospheric methane is one of the only biosignatures that may be readily detectable with NASA’s recently launched James Webb Space Telescope. Therefore, it is imperative that we have a comprehensive understanding of when methane is a good exoplanet biosignature. In this study, I used a photochemical model to investigate how large of a methane surface flux is necessary to sustain significant atmospheric methane abundances. I also explored different abiotic sources that can produce atmospheric methane (e.g., magmatic outgassing, low-temperature water-rock and metamorphic reactions) to determine if, under diverse planetary conditions, these abiotic sources could cause a false positive that would be challenging to rule out using observable clues. This work provides a preliminary framework for identifying methane biosignatures that takes into account the broader planetary and astrophysical context. This paper has been published in PNAS (Thompson et al., PNAS 119 (14), 2022). Stay tuned for more work on this topic!

• I also worked on a Perspectives article for Nature Astronomy on the importance of comprehensively understanding planetary context when assessing potential signs of life on exoplanets (Krissansen-Totton et al. 2022).

Carnegie Institution for Science EPL Research (2016-2017 Academic Year)

• 9-month Astronomy Research Trainee position under the mentorship of Dr. Alycia Weinberger. I analyzed data of an unusually warm, dusty debris disk around a binary star system (BD +20 307) from the Stratospheric Observatory for Infrared Astronomy (SOFIA) and comparing this epoch of data to two earlier epochs taken with Spitzer and Keck/Gemini to see if we can understand the evolution of this system's dust (Thompson et al. 2019). Check out NASA’s press release article on our work (“When Exoplanets Collide”).

• While at DTM, I also worked with Drs. Alan Boss and Serge Dieterich conducting analysis for the Carnegie Astrometric Planet Search program which aims to astrometrically detect exoplanets and brown dwarf companions using data from the CAPSCam camera on the 2.5-meter du Pont Telescope at the Las Campanas Observatory in Chile, and combining data from CAPSCam with that from the recent Gaia satellite data release. (Dieterich et al. 2018)

Undergraduate Senior Thesis Research (2015-2016 Academic Year)

• 8-month Senior Thesis research project under the mentorship of Professor David Spergel. Developed an original approximate model to aid in the astrometric detection and characterization of multiple exoplanet systems. Wrote Python code to model stellar motion in over 50 hypothetical two- and three-exoplanet systems and incorporated a least-squares fit program to assess its efficiency in planet characterization.