Towards HADES: Deeply probing of Lava World Atmospheres

Transmission spectroscopy of exoplanet atmospheres enables us to infer the characteristics of planets in foreign stellar systems. Terrestrial planets are of special interest as they increase our understanding of their origin and evolution preparing us to characterize a true Earth-analog planet in the future. Recent discoveries confirmed the presence of rocky planets in very short orbits, resulting in surface temperatures above the critical value of 2000K, where the surface rocks start to melt and release silicates into the atmosphere. Such worlds are denoted as Lava worlds and show different molecules with a large number of absorption lines.

Such molecules allow us to characterize lava world atmospheres even with ground-based high-resolution transit observations applying the cross-correlation method. More specifically, by applying injection recovery, in which template spectra are injected and recovered from the observations, it is possible to infer the lower limit of the atmospheric mean-molecular weight value, giving key insights into the atmospheric redox-state, recycling efficiency of atmophile elements between the melt-pool and solid-interior and atmospheric composition of lava worlds.

Recent JWST observations showed the likely presence of a CO/CO2 dominated atmosphere on the rocky planet 55 CNC e inferred from eclipse observations. This hints at the absence of a tenuous vaporized rock atmosphere, and the presence of a volatile dominated atmosphere. A volatile-rich atmosphere would result in a low mean-molecular weight atmosphere, making it possible to be inferred by applying ground-based observations.

We present several recent ground-based high-spectral resolution (R = 50 000) observations of 55 CNC e acquired at the Large-Binocular- telescope with the PEPSI instrument and show preliminary results on the inferred mean-molecular weight value. We compare this to the recent JWST results and discuss the implication of the results concerning the atmospheric redox state and the recycling efficiency of atmophile elements between the melt pool and solid interior.