Composition of Terrestrial Exoplanet Atmospheres from Meteorite Outgassing Experiments

TL;DR

This study uses laboratory outgassing experiments on meteorite samples to provide empirical data on the initial atmospheric compositions of terrestrial exoplanets, linking planetary building blocks to atmospheric properties.

Contribution

It offers the first experimental constraints on initial atmospheric compositions derived from meteorite outgassing, informing models of terrestrial planet atmospheres.

Findings

Meteorite outgassing produces H2O-rich atmospheres (~66%)

Significant amounts of CO (~18%) and CO2 (~15%) are released

Results supply principal gas abundances as a function of temperature

Abstract

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, 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 1200 $^{\circ}$C. We find that outgassing from three carbonaceous chondrite samples consistently produce H$_2$O-rich (averaged ~66 %) atmospheres but with significant 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, supplying abundances for principal gas species as a function of temperature.