Characterizing Lava Worlds – Critical Laboratory Work for Observations

Lava worlds are exoplanets characterized by intense irradiation and equilibrium temperatures > 1500 K that can maintain a (partially) molten state surface. The unique high-temperature environment of lava worlds offers an opportunity for direct observations of their surfaces with JWST and explore their composition. To that end, a reference library of the radiative properties of diverse (partially) molten surface materials is critical but currently missing. Here, we present a new laboratory instrument that characterizes the InfraRed radiative properties of any solid or molten materials at the micro-scale up to 1773 K. To establish such a reference library, we describe the instrumental setup to prepare, calibrate, and measure such samples as well as first results for in situ measurements of emissivity spectra of magma products with various possible compositions analog to lava worlds. Based on these data, we discuss the importance of IR high-temperature emissivity measurements and their applicability to lava world observations, identify key spectral features linked to molecular species, and describe the relations between the radiative properties, temperature, composition, and wavelength. Linking the interpretations of IR spectra of possible lava world compositions to JWST observations will offer clues about their underlying geological and geochemical processes. The database will provide a tool for modelers and observers to interpret telescopic observations and advance our understanding of the composition and formation of rocky planets in tight orbits around their host stars. Lava worlds enable us to refine our understanding of planetary diversity and the factors influencing the habitability of other worlds in our galaxy.