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

Formaldehyde (H₂CO) 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 H₂. However, it remains uncertain whether such a temperate and weakly reducing surface environment on early Mars was suitable for producing H₂CO. In this study, we investigated the atmospheric production of H₂CO on early Mars using a 1-D photochemical model assuming a thick CO₂-dominated atmosphere with H₂ and CO. Our results show that a continuous supply of atmospheric H₂CO 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 H₂CO into ribose, the calculated H₂CO deposition flux suggests a continuous supply of bio-important sugars on early Mars, particularly during the Noachian and early Hesperian periods.