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 perform outgassing experiments in the laboratory in which I heat a wide variety of meteorite samples at carefully controlled rates to temperatures up to 1200 ℃ and measure the abundances of released volatiles (e.g., H2O, CO, CO2, H2, H2S) as a function of temperature and time. This work provides experimental constraints on the initial chemical abundances in theoretical models.