Chlorate Chemistry From Earth to Mars

Isotopic measurements indicate that chlorate and perchlorate form naturally via atmospheric oxidation of chlorine compounds, but detailed mechanisms, particularly for the more reactive chlorate, remain poorly constrained. Chan et al. (2025, https://doi.org/10.1029/2024JD042162) incorporated chlorate and perchlorate chemistry and isotopic fingerprinting into a chemical transport model. Discrepancies between observed and modeled concentrations and isotopic values highlight missing processes especially multiphase reactions of chlorate. The future directions outlined in this commentary may help clarify atmospheric chlorate chemistry and its interaction with other trace species. Given the widespread occurrence of chlorate and perchlorate on Mars, improved understanding of chlorate chemistry will inform their roles in liquid water stability, organic preservation, planetary habitability, and the search of potential Martian biosignatures.