Haze Evolution in Temperate Exoplanet Atmospheres Through Surface Energy Measurements

TL;DR

This study measures surface energies of temperate exoplanet hazes to understand haze removal processes, revealing temperature-dependent variations that influence atmospheric haziness and potential habitability.

Contribution

Provides the first experimental measurements of haze surface energies under exoplanetary conditions, linking haze removal physics to planetary temperature and composition.

Findings

Surface energies vary significantly with temperature and atmospheric conditions.

Lowest haze removal rates occur around 400 K for cold plasma samples.

Haze surface energy correlates with atmospheric haziness and planetary temperature.

Abstract

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 is 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 which can be removed efficiently.