Haze evolution in temperate exoplanet atmospheres through surface energy measurements

• Published in: Nature astronomy Vol. 5; no. 8; pp. 822 - 831
• Main Authors: Yu, Xinting, He, Chao, Zhang, Xi, Hörst, Sarah M., Dymont, Austin H., McGuiggan, Patricia, Moses, Julianne I., Lewis, Nikole K., Fortney, Jonathan J., Gao, Peter, Kempton, Eliza M.-R., Moran, Sarah E., Morley, Caroline V., Powell, Diana, Valenti, Jeff A., Vuitton, Véronique
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group 01.08.2021
• Subjects: Astronomy; Astrophysics; Atmosphere; Atmospheric aerosols; Cold; Contact angle; Earth; Earth and Planetary Astrophysics; Energy resources; Energy sources; Equilibrium; Haze; Laboratories; Opacity; Photochemicals; Physics; Plasma; Science; Sciences of the Universe; Astrophysics - Earth and Planetary Astrophysics
• DOI: 10.1038/s41550-021-01375-3
• ISSN: 2397-3366

Photochemical hazes are important opacity sources in temperate exoplanet atmospheres, hindering current observations from characterizing exoplanet atmospheric compositions. The haziness of an atmosphere is determined by the balance between haze production and removal. However, the material-dependent removal physics of the haze particles are currently unknown under exoplanetary conditions. Here we provide experimentally measured surface energies for a grid of temperate exoplanet hazes to characterize haze removal in exoplanetary atmospheres. We found large variations of surface energies for hazes produced under different energy sources, atmospheric compositions and temperatures. The surface energies of the hazes were found to be the lowest around 400 K for the cold plasma samples, leading to the lowest removal rates. We show a suggestive correlation between haze surface energy and atmospheric haziness with planetary equilibrium temperature. We hypothesize that habitable-zone exoplanets could be less hazy, as they would possess high-surface-energy hazes that can be removed efficiently.Photochemical hazes in exoplanet atmospheres work as opacity barriers, hindering characterization of the atmospheres themselves. Here laboratory experiments quantify the haze surface energies that factor into the removal of hazes from atmospheres, which, when added to existing data on haze production, give a greater understanding of haze properties.