Earth and Planetary Science Letters 473 (2017) 113–121 Contents lists available at ScienceDirect Earth and Planetary Science Letters www.elsevier.com/locate/epsl Production of reactive oxygen species from abraded silicates. Implications for the reactivity of the Martian soil Ebbe N. Bak a,∗ , Kaloyan Zafirov a , Jonathan P. Merrison b , Svend J. Knak Jensen c , Per Nørnberg a , Haraldur P. Gunnlaugsson d , Kai Finster a,e a Department of Bioscience, Aarhus University, Ny Munkegade 116, 8000 Aarhus C, Denmark b Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark c Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus C, Denmark d ISOLDE, PH Department, CERN, CH-1211 Geneve 23, Switzerland e Stellar Astrophysics Center, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark a r t i c l e i n f o a b s t r a c t Article history: Received 23 June 2016 Received in revised form 3 January 2017 Accepted 3 June 2017 Available online xxxx Editor: C. Sotin Keywords: Mars wind driven erosion hydrogen peroxide habitability Viking stress factor The results of the Labeled Release and the Gas Exchange experiments conducted on Mars by the Viking Landers show that compounds in the Martian soil can cause oxidation of organics and a release of oxygen in the presence of water. Several sources have been proposed for the oxidizing compounds, but none has been validated in situ and the cause of the observed oxidation has not been resolved. In this study, laboratory simulations of saltation were conducted to examine if and under which conditions wind abrasion of silicates, a process that is common on the Martian surface, can give rise to oxidants in the form of hydrogen peroxide (H 2 O 2 ) and hydroxyl radicals (·OH). We found that silicate samples abraded in simulated Martian atmospheres gave rise to a significant production of H 2 O 2 and ·OH upon contact with water. Our experiments demonstrated that abraded silicates could lead to a production of H 2 O 2 facilitated by atmospheric O 2 and inhibited by carbon dioxide. Furthermore, during simulated saltation the silicate particles became triboelectrically charged and at pressures similar to the Martian surface pressure we observed glow discharges. Electrical discharges can cause dissociation of CO 2 and through subsequent reactions lead to a production of H 2 O 2 . These results indicate that the reactions linked to electrical discharges are the dominant source of H 2 O 2 during saltation of silicates in a simulated Martian atmosphere, given the low pressure and the relatively high concentration of CO 2 . Our experiments provide evidence that wind driven abrasion could enhance the reactivity of the Martian soil and thereby could have contributed to the oxidation of organic compounds and the O 2 release observed in the Labeled Release and the Gas Exchange experiments. Furthermore, the release of H 2 O 2 and ·OH from abraded silicates could have a negative effect on the persistence of organic compounds in the Martian soil and the habitability of the Martian surface.  2017 Elsevier B.V. All rights reserved. 1. Introduction Our understanding of Mars as a habitat for past and present life is closely linked to insight into the chemistry of its surface soil as soil chemistry affects the stability of organic compounds as well as the survival of organisms. Thus, a better qualitative and quantitative understanding of the reactivity of the Martian soil is essential for evaluation of the persistence of organic biomarkers, the risk of forward contamination and for identification of poten- tial habitable sites. The Labeled Release (LR) experiment conducted * Corresponding author. E-mail address: ebbe.bak@bios.au.dk (E.N. Bak). by the Viking Landers demonstrated that simple 14 C-labeled or- ganic compounds in an aqueous medium were oxidized with a concomitant release of 14 CO 2 when exposed to Martian soil (Levin and Straat, 1979). Furthermore, the Gas Exchange (GEx) experi- ment showed that Martian soil exposed to water vapor released O 2 at higher quantities than what could be accounted for by atmospheric O 2 adsorbed on the sample surfaces (Oyama and Berdahl, 1977). Based on these observations, it has been proposed that one or more reactive oxygen species (ROS) are present in the Martian soil (Ballou et al., 1978; Klein, 1978). Specifically, H 2 O 2 , at least as an intermediate, has been held responsible for the reactivity observed by the LR and GEx experiments as dis- proportionation of H 2 O 2 can lead to a release of O 2 and be- cause H 2 O 2 can oxidize organic compounds to CO 2 if catalyzed http://dx.doi.org/10.1016/j.epsl.2017.06.008 0012-821X/ 2017 Elsevier B.V. All rights reserved.