The possible fate of formaldehyde (H2CO) generated by atmospheric chemistry on Paleo-Mars

The preservation of ancient organic material (e.g., Stern et al. 2015, 2017, 2018; Glavin et al. 2013) in the regolith of Mars is a special “gift” to our Solar System. By comparison, active plate tectonics on Earth has obliterated any record of pristine material that led to the origin of life. The Mars Sample Return (MSR) program specifically emphasizes 1. Extant or recent Martian life and 2. Biosignatures of past Martian life (Meyer et al. 2022). Here we report preliminary results of organics (H2CO) generated by atmospheric chemistry (Pinto et al. 1980). We extended the Caltech/JPL KINETICS model to include aqueous chemistry, a platform we name KINAQA. KINAQA solves the continuity equation to consider chemical production and loss. KINAQA currently considers 26 aqueous species linked by 50 reactions and is under development for expansion. We run KINAQA over a thin 4-layer box model (ignoring large-scale transport), unlike KINETICS which uses 2-3 layers per atmospheric scale height and considers molecular and eddy diffusion between levels. We conclude from atmospheric KINETICS runs that the most likely fate of H2CO is conversion to glyoxal, followed by oxidation in the aqueous phase to formate and potentially to other carboxylic acids using nitrate or H2O2 as oxidants (Zhang et al. 2021).