Isotopes of chlorine from HCl in the Martian atmosphere

Alexander Trokhimovskiy (1) , Anna Fedorova (1) , Kevin Olsen , Juan Alday (2) , Oleg Korablev (1) , Franck Montmessin (3) , Franck Lefèvre (3) , Andrey Patrakeev (1) , Denis Belyaev (1) , Alexey Shakun (1)

1 IKI - Space Research Institute of the Russian Academy of Sciences
2 Department of Physics [Oxford]
3 PLANETO - LATMOS

Hydrogen chloride gas was recently discovered in the atmosphere of Mars during southern summer seasons. Its connection with potential chlorine reservoirs and the related atmospheric chemistry is now of particular interest and actively studied. Measurements by the Atmospheric Chemistry Suite mid-infrared channel (ACS MIR) on the ExoMars Trace Gas Orbiter allow us to measure the ratio of hydrogen chloride two stable isotopologues, H35Cl and H37Cl. This work describes the observation, processing technique, and derived values for the chloride isotope ratio. Unlike other volatiles in the Martian atmosphere, because it is enriched with heavier isotopes, the δ37Cl is measured to be − 7 ± 20°, which is almost indistinguishable from the terrestrial ratio for chlorine. This value agrees with available measurements of the surface materials on Mars. We conclude that chlorine in observed HCl likely originates from dust and is not involved in any long-term, surface-atmosphere cycle.

Domaines: Planète et Univers [physics]

Alexander Trokhimovskiy, Anna Fedorova, Kevin Olsen, Juan Alday, Oleg Korablev, et al.. Isotopes of chlorine from HCl in the Martian atmosphere. Astronomy and Astrophysics - A&A, 2021, 651, A32 (7 pp.). ⟨10.1051/0004-6361/202140916⟩. ⟨insu-03238520⟩