In situ detection of chlorine dioxide (clo₂) in the radiolysis of perchlorates and implications for the stability of organics on mars

Magnesium perchlorate hexahydrate (Mg(ClO₄)₂ · 6H₂O) samples were exposed to energetic electrons to investigate the products of the decomposition of perchlorates in the Martian soil and to infer their role in the degradation of organics on Mars. The samples were monitored online and in situ via infrared spectroscopy as well as electron impact (EI-QMS) and reflectron time-of-flight mass spectrometry coupled with single photon ionization (PI-ReTOF-MS). Our study reveals that besides chlorates (${{ClO}_3}^{-}$) and molecular oxygen (O₂), the chlorine dioxide radical (ClO₂) was observed online and in situ for the first time as a radiolysis product of solid perchlorates. Chlorine dioxide, which is used on Earth as a strong oxidizing agent in water disinfection and bleaching, represents a proficient oxidizer—potentially more powerful than molecular oxygen—to explain the lack of abundant organics in the Martian soil.