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Laboratory experiments show that sand grain saltation in a Mars-like environment can result in the ionization of argon. This suggests that saltation can be a mechanism for the destruction of methane (CH4) on Mars given the ionization energy of argon is higher than the energy required to ionize methane to a reactive cation. The ionization energy is also higher than the energy to dissociate methane to highly reactive species like CH3, CH2, and CH. The feasibility of capturing the resulting emission glow on a windy Martian night is discussed.

Numerous studies have demonstrated that the martian surface environment is hostile to life because of its rough radiation climate and the reactive chemistry of the regolith. Physical processes such as erosion and transport of mineral particles by wind-driven saltation have hitherto not been considered as a life hazard. We report a series of experiments where bacterial endospores (spores of Bacillus subtilis) were exposed to a simulated saltating martian environment. We observed that 50% of the spores that are known to be highly resistant to radiation and oxidizing chemicals were destroyed by saltation-mediated abrasion within one minute. Scanning electron micrographs show that the spores were not only damaged by abrasion but were eradicated during the saltation process. We suggest that abrasion mediated by wind-driven saltation should be included as a factor that defines the habitability of the martian surface environment. The process may efficiently protect the martian surface from forward contamination with terrestrial microbial life-forms. Abrasion mediated by wind-driven saltation should also be considered as a major challenge to indigenous martian surface life if it exists/existed.

A new kind of solid gas chemical reactions has been investigated using solid-state powder H-2, C-13, and Si-29 NMR and EPR spectroscopies. These studies involve reactions between a silicate-created Si free-radical intermediate and a few ordinary gases such as isotopically H-2-, C-13-, and O-17-enriched methane ((CH4)-C-13 and CD4), carbon dioxide ((CO2)-C-13), hydrogen (H-2(2)) and oxygen (O-17(2)). The solid-state Si free-radical intermediate and gas reaction and silicate products are formed in a specially designed rotating apparatus, which by mechanical tumbling mimics the winds and collision speed of the mineral particles on Mars. It is shown that the "hard" quartz (SiO2) or corundum (alpha-AL(2)O(3)) grain particles, used to simulate the collision particles in a rotating Pyrex (borosilicate) reaction flask, act as an abrasive on the "soft" Pyrex flask and thereby create a silicate Si free-radical intermediate. EPR studies show that this radical is identical to the silicate radical intensively investigated by EPR from gamma-irradiation of Pyrex and other glasses and shown to constitute a submicrostructure of either silicate chains or helices. The intensity of the silicate Si free-radical EPR signal for the reaction product is strongly reduced or even disappears by performing the tumbling of the abrasive grain particles in an atmosphere of methane or other gases. C-13{H-1} and Si-29{H-1} CP/MAS NMR experiments of the reaction product with methane gas show the presence of one -bond CH3-Si equivalent to and HO-Si equivalent to covalent bonds in its structure and that sieving the product leads to a sensitivity enhancement by a factor of similar to 25. A flexible helical structure for the silicate Si free-radical intermediate is indicated by the preliminary results for the product resulting from the reaction with (CO2)-C-13, (encapsulation of the gas) and the indication of a congested methyl group in the product from reaction with methane.

The only organic compounds that have been detected in the Martian soil are simple chlorinated compounds released from heated surface material. However, the sources of the organic carbon are in dispute. Wind abraded silicates, which are widespread on the Martian surface, can sequester atmospheric methane which generates methylated silicates and thus could provide a mechanism for accumulation of reduced carbon in the surface soil. In this study we show that thermal volatilization of methylated silicates in the presence of perchlorate leads to the production of chlorinated methane. Thus, methylated silicates could be a source of the organic carbon released as chlorinated methane upon thermal volatilization of Martian soil samples. Further, our experiments show that the ratio of the different chlorinated compounds produced is dependent on the mass ratio of perchlorate to organic carbon in the soil.

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.

We have undertaken a set of wind erosion experiments on a simple and well defined mineral, quartz. In these experiments wind action is simulated by end over end tumbling of quartz grains in a sealed quartz flask. The tumbling induces collisions among the quartz grains and the walls of the flask. This process simulates wind action impact speed of ∼1.2 m/s. After several months of tumbling we observed the formation of a large number of spherical sand aggregates, which resemble small snowballs under optical microscopy. Upon mechanical load the aggregates are seen to be more elastic than quartz and their mechanical strength is comparable, though slightly lower than that of sintered silica aerogels. Aggregates of this kind have not been reported from field sites or from closed circulation systems. However, sparse occurrence might explain this, or in nature the concentration of the aggregate building particles is so low that they never meet and just appear as the most fine grained tail of the sediment particle size distribution.