Photochemistry and haze in chemically reducing terrestrial atmospheres.

Properties and processes within planetary atmospheres are critical for surface habitability. Evidence from the Earth suggests that our only known form of life has likely originated in a chemically reducing atmosphere. The photochemistry and haze formation in such environments played an important role in the emergence and sustenance of early life, yet these processes have received insufficient attention due to reliance on outdated laboratory measurements and numerical simulations. This perspective aims to highlight the importance of chemically reducing terrestrial atmospheres, elucidate the key chemical and physical processes involved, and propose integrated experimental and modeling strategies to overcome current limitations.