Faculty of Natural Sciences

TY - JOUR

T1 - Production of reactive oxygen species from abraded silicates. Implications for the reactivity of the Martian soil

AU - Bak, Ebbe N.

AU - Zafirov, Kaloyan

AU - Merrison, Jonathan P.

AU - Jensen, Svend J. Knak

AU - Nornberg, Per

AU - Gunnlaugsson, Haraldur P.

AU - Finster, Kai

PY - 2017/9/1

Y1 - 2017/9/1

N2 - 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 (H2O2) and hydroxyl radicals (center dot OH). We found that silicate samples abraded in simulated Martian atmospheres gave rise to a significant production of H2O2 and center dot 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 CO2 and through subsequent reactions lead to a production of H2O2. These results indicate that the reactions linked to electrical discharges are the dominant source of H2O2 during saltation of silicates in a simulated Martian atmosphere, given the low pressure and the relatively high concentration of CO2. 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 H2O2 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. (C) 2017 Elsevier B.V. All rights reserved.

AB - 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 (H2O2) and hydroxyl radicals (center dot OH). We found that silicate samples abraded in simulated Martian atmospheres gave rise to a significant production of H2O2 and center dot 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 CO2 and through subsequent reactions lead to a production of H2O2. These results indicate that the reactions linked to electrical discharges are the dominant source of H2O2 during saltation of silicates in a simulated Martian atmosphere, given the low pressure and the relatively high concentration of CO2. 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 H2O2 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. (C) 2017 Elsevier B.V. All rights reserved.

KW - Mars

KW - wind driven erosion

KW - hydrogen peroxide

KW - habitability

KW - Viking

KW - stress factor

KW - OXIDANT ENHANCEMENT

KW - HYDROGEN-PEROXIDE

KW - CURIOSITY ROVER

KW - GALE CRATER

KW - DUST DEVILS

KW - MARS

KW - PERCHLORATE

KW - GENERATION

KW - CHEMISTRY

KW - SURFACE

U2 - 10.1016/j.epsl.2017.06.008

DO - 10.1016/j.epsl.2017.06.008

M3 - Journal article

VL - 473

SP - 113

EP - 121

JO - Earth and Planetary Science Letters

JF - Earth and Planetary Science Letters

SN - 0012-821X

ER -