The chemistry induced by stellar radiation and energetic particles produces haze particles in planetary atmospheres, which happens on many Solar System bodies and are expected in exoplanetary atmospheres. Haze particles play an important role in planetary atmospheres, affecting both physical and chemical processes in the atmospheres and on the surface if the planets are terrestrial. However, the chemical processes that lead to haze formation are poorly understood in exoplanet atmospheres because their atmospheric parameters are different from that in Solar System bodies. Here, we present the results from our laboratory experiments simulating a range of exoplanet atmospheres. We carried out the experiments by using the Planetary HAZE Research (PHAZER) chamber at Johns Hopkins University with one of two energy sources (AC glow plasma or UV photons) to initiate chemical reactions. All simulated atmospheres resulted in the formation of haze particles with great diversity in haze production rates (He et al. 2018a, 2020a, b; Hörst et al. 2018a). We tracked the gas phase compositional changes with a mass spectrometry during the experiments, which indicates that different chemical pathways are responsible for generating organic haze in different simulated atmospheres (He et al. 2019). The characterization of the resulting organic haze particles reveals distinct physical and chemical properties (color, size distribution, surface energy, and composition) of these hazes (He et al. 2018a, 2018b, 2020a, 2020b, Moran et al. 2020, Vuitton et al. 2021). The laboratory results increase our understanding of orgainc haze formation in exoplanet atmospheres, and can help to guide atmosphere modeling and observations of exoplanets.

Photochemical haze formation in exoplanetary atmospheres: Insight from laboratory simulations

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.