Isotope Effects (Cl, O, C) of Heterogeneous Electrochemistry Induced by Martian Dust Activities

Session: Advancing Mineral Science and Exploring Planetary Surfaces: In Honor of MSA Dana Medalist, Elizabeth B. Rampe (Posters)

Presenting Author:

Alian Wang

Authors:

Wang, Alian¹, Sturchio, Neil C.², Yan, Hao³, Jacson, Andrew⁴, Bao, Huiming⁵, Yan, Chuck Y. C.⁶, Qu, Quincy H. K.⁷, Olsen, Kevin S⁸, Heraty, Linnea J.⁹, Wei, Yu¹⁰

(1) Earth, Environmental, and Planetary Science, Washington University in St. Louis, St. Louis, MO, USA, (2) Earth Science, University of Delware, Newark, Delware, USA, (3) Earth Science and Engineering, Nanjing University, Nanjing, China, (4) Civil, Environmental, and Construction Engineering, Texas Tech University, Lubbock, Texas, USA, (5) Earth Science and Engineering, Nanjing University, Nanjing, China, (6) Earth, Environmental, and Planetary Sciences, Washington University in St. Louis, St. Louis, MO, USA, (7) Earth, Environmental, and Planetary Sciences, Washington University in St. Louis, St. Louis, MO, USA; Space science and Physics, Shandong University at Weihai, WeiHai, China, (8) Physics, University of Oxford, Oxford, United Kingdom, (9) Earth Science, University of Delware, Newark, Delware, USA, (10) Earth Science and Engineering, Nanjing University, Nanjing, China,

Abstract:

Some of the oxidized compounds in Martian soils are suspected of being produced by heterogeneous electrochemistry (HEC) stimulated by electrostatic discharge (ESD) that is associated with dust activities (dust storms and dust devils) on the surface of Mars. One approach to distinguish HEC products could be to experimentally characterize their isotopic compositions; this may provide an improved basis for interpreting the isotopic compositions of Martian surface materials. Here, we measured isotopic compositions of Cl, O, and C in reactants and products from medium-strength ESD experiments conducted in a Mars simulation chamber (Wang et al., 2023).  Results of these isotopic measurements on chloride, (per)chlorate, and carbonate as ESD products show substantial mass-dependent depletions in heavy isotopes, with e³⁷Cl ranging from -11.3 ‰ to +2.0 ‰, e¹⁸O from -34.5 ‰ to -12.9 ‰, and e¹³C around -11.4 ‰. These isotope characteristics suggest that the lighter isotopes are preferred in the newly generated volatile species (Cl_I^*, O_I^*, O₃, CO₂⁺, and CO^*) during the breakdown of chlorides and CO₂ when impacted by energetic electrons, then being embedded in the consequent Cl-depots and air-born carbonates.  These results, when compared with isotopic measurements from recent Mars missions (ESA’s ExoMars Trace Gas Orbiter and the Sample Analysis at Mars (SAM) instrument package aboard NASA’s Curiosity rover) and Martian meteorites, support the hypothesis that HEC induced by Martian dust activities can account for a substantial portion of the Cl-species and carbonates identified at the surface of Mars.