Kimberly Paragas (Caltech)

JWST’s Mid InfraRed Instrument (MIRI) provides a unique opportunity to spectroscopically characterize the surface compositions of terrestrial exoplanets for the first time. Close-in, rocky planets orbiting M dwarfs are ideal targets for these studies, and recent Spitzer and JWST measurements have shown that many have little to no atmosphere. There are currently six hot rocky exoplanets, including LHS 3844 b, with approved JWST programs to measure their thermal emission spectra with MIRI LRS. Current models for the bare-rock spectra of these planets utilize a spectral library spanning a limited number of surface types. This library was also measured at room temperature, and does not capture temperature-dependent changes in spectral feature shapes. Here we present a new spectral library that includes a larger variety of rock types with varying textures (solid slab, coarsely crushed, and fine powder), as well as high temperature (up to 830 K) emissivity measurements for select samples. We use this new library to highlight the importance of spectroscopically resolved measurements for constraining the surface compositions of hot, rocky exoplanets.