Understanding the chemistry of temperate exoplanet atmospheres: A study of oxidized organic compounds as precursors of photochemical condensates
Résumé
Characterizing the atmospheres of small temperate exoplanets is a major scientific challenge. The James Webb Space Telescope offers us the opportunity to study temperate exoplanets as small as mini-Neptunes. Recent observations of K2-18 b and TOI-270 d have revealed atmospheres rich in hydrogen and carbon compounds. Methane and carbon dioxide have been detected in significant amounts. The development of our knowledge of these atmospheres will enable us to characterize their habitability. However, our understanding of the chemistry governing these atmospheres remains very limited. Therefore, laboratory experiments and modeling are needed to better understand these observations. In this context, we have carried out experimental simulations. Using a cold plasma reactor, we simulated the out-of-equilibrium chemistry that occurs in the upper layers of temperate exoplanets. We have used mass spectrometry and infrared spectroscopy to track the chemical evolution of gas mixtures similar to exoplanetary atmospheres. Our observations highlight the production of complex organic compounds, carbon monoxide, and water vapor. In addition, our first results suggest the formation of oxidized organic compounds, which are precursors of photochemical condensates of prebiotic interest.
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