Composition of terrestrial exoplanet atmospheres from meteorite outgassing experiments

• Published in: Nature astronomy Vol. 5; no. 6; pp. 575 - 585
• Main Authors: Thompson, Maggie A., Telus, Myriam, Schaefer, Laura, Fortney, Jonathan J., Joshi, Toyanath, Lederman, David
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.06.2021; Nature Publishing Group
• Subjects: 639/33/445/824; 639/33/445/862; Accretion; Astronomy; Astrophysics and Cosmology; Atmosphere; Carbon dioxide; Experiments; Hydrogen sulfide; Laboratories; Meteors & meteorites; Physics; Physics and Astronomy; Planets; Terrestrial environments
• ISSN: 2397-3366; 2397-3366
• DOI: 10.1038/s41550-021-01338-8

Terrestrial exoplanets likely form initial atmospheres through outgassing during and after accretion, although there is currently no first-principles understanding of how to connect a planet’s bulk composition to its early atmospheric properties. Important insights into this connection can be gained by assaying meteorites, which are representative samples of planetary building blocks. We perform laboratory outgassing experiments that use a mass spectrometer to measure the abundances of volatiles released when meteorite samples are heated to 1,200 °C. We find that outgassing from three carbonaceous chondrite samples consistently produce H 2 O-rich (average of ~66%) atmospheres but with substantial amounts of CO (~18%) and CO 2 (~15%) as well as smaller quantities of H 2 and H 2 S (up to 1%). These results provide experimental constraints on the initial chemical composition in theoretical models of terrestrial planet atmospheres, and supply abundances for principal gas species as a function of temperature. Laboratory experiments where meteorites are heated up to 1,200 °C are performed in order to inform on the outgassing from exoplanetary interiors. Differing considerably from assumptions commonly used by models, the experiments indicate that terrestrial planets would form water-rich steam atmospheres with substantial amounts of CO 2 and CO.