Atmospheric formaldehyde production on early Mars leading to a potential formation of bio-important molecules

Formaldehyde (H 2 CO) is a critical precursor for the abiotic formation of biomolecules, including amino acids and sugars, which are the building blocks of proteins and RNA. Geomorphological and geochemical evidence on Mars indicates a temperate environment compatible with the existence of surface liquid water during its early history at 3.8–3.6 billion years ago (Ga), which was maintained by the warming effect of reducing gases, such as H 2 . However, it remains uncertain whether such a temperate and weakly reducing surface environment on early Mars was suitable for producing H 2 CO. In this study, we investigated the atmospheric production of H 2 CO on early Mars using a 1-D photochemical model assuming a thick CO 2 -dominated atmosphere with H 2 and CO. Our results show that a continuous supply of atmospheric H 2 CO can be used to form various organic compounds, including amino acids and sugars. This could be a possible origin for the organic matter observed on the Martian surface. Given the previously reported conversion rate from H 2 CO into ribose, the calculated H 2 CO deposition flux suggests a continuous supply of bio-important sugars on early Mars, particularly during the Noachian and early Hesperian periods.