The dominant source of methane (CH4) on Earth is biological and thus a sign of life. Therefore, the discovery of CH4 in the Martian atmosphere was sensational and attracted a lot of attention both within the science community and in the public. Since its discovery, we have learned that the concentration of CH4 on Mars is very dynamic and follows an annual cycle with relatively high concentration during Martian summer and low concentration during winter. Until now the drivers behind this dynamic pattern remain enigmatic as photochemistry which stands behind most atmospheric processes on Mars is too slow to explain the rapid decline. We studied wind-driven erosion as known from dust-devils and/or sand storms and explored whether it can work as a rapid CH4 sink. The outcome of this study will be reported in my presentation.

We investigate the triboelectrically driven reduction of quartz sand when mechanically abraded (i.e., tumbled) in an atmosphere of hydrogen gas. Using diffuse reflectance IR spectroscopy, solid-state NMR spectroscopy, and quantum chemical computations, we show that hydrogen is incorporated into the abraded quartz sand in the form of silanol (Si-OH) and silane (Si-H) surface moieties. Furthermore, we use electron paramagnetic resonance (EPR) spectroscopy to characterize the paramagnetic radicals that are formed on the surface of the quartz sand particles during erosion. These radicals are stable when stored in ambient air for at least 6 months and they tolerate heating up to temperatures of similar to 230 degrees C. The radicals are partially quenched by sonication in water.

Aerosols, including biological aerosols, exert a significant influence on cloud formation, influencing the global climate through their effects on radiative balance and precipitation. The Arctic region features persistent mixed-phase clouds, which are impacted by ice nucleating particles (INPs) that modulate the phase transitions within clouds, affecting their lifetime and impacting the region's climate. An increasing number of studies document that Arctic soils harbor numerous biogenic INPs (bioINPs), but these have yet to be linked to their microbial producers. In addition, the transfer of bioINPs from soils into freshwater and marine systems has not been quantified. This study aimed to address these open questions by analyzing soil and freshwater samples from northeast Greenland to determine the microbial composition along with the INP concentrations and size distributions. We found that soils contained between 3.19×104 and 1.55×106 INP g−1 soil, which was on the lower side of what has previously been reported for active-layer soils. The composition of INPs varied widely across locations and could have originated from bacterial and fungal sources. We detected Mortierella, a fungal genus known to produce ice nucleating proteins, at nearly all locations. Spearman correlations between soil taxa and INP concentrations pointed at lichenized fungi as a possible contributor to soil INP. Additionally, based on the INP size distribution, we suggest that soil INPs were bound to soil particles or microbial membranes at some locations, while other locations showed a variety of soluble INPs with different molecular sizes. In streams, INP concentrations were comparable to what has previously been measured in streams from temperate regions. Interestingly, stream INP concentrations showed a positive association with soil INP concentrations. The potential release and aerosolization of these bioINPs into the atmosphere – whether directly from the soil, from streams into which they are washed, or from the oceans where they might be transported – could impact cloud formation and precipitation patterns in the Arctic. This research contributes valuable knowledge to the understanding of microbial communities and the potential microbial producers of highly active bioINPs in Arctic soils and their connectivity with Arctic streams.

Mechanical activation of quartz grains in a dry atmosphere causes triboelectric charging that can capture CO2 quantitatively (Thogersen et al., https://doi.org/10.1016/j.cplett.2021.139069). Based on electron structure calculations, we propose a mechanism for this process. According to the mechanism, CO2 is inserted in the quartz lattice to form an anchored CO3 moiety. Predicted 13C chemical shifts of this product agree with solid-state 13C NMR measurements.

Mechanical activation (i.e., tumbling) of quartz sandin a carbondioxide (CO2) atmosphere leads to triboelectric chargingof the sand grains, driving a process that ultimately sequesters andremoves CO2 from the ambient atmosphere. Supported by diffusereflectance FTIR and C-13 solid-state NMR experiments anddensity functional theory (DFT) calculations, we propose that CO2 is inserted into the quartz lattice to form an anchored CO3 species, a process that otherwise requires high temperatureand pressure to proceed synthetically. The products of the reactionare stable for at least 6 months at ambient temperature and pressure,but CO2 is liberated at temperatures above 150 degrees C.The prospect of using this method to remove CO2 from theatmosphere and, ultimately, to help mitigate the adverse effects ofgreenhouse gases and global warming is briefly discussed.

Since the Viking Labeled Release experiments were carried out on Mars in the 1970s, it has been evident that the martian surface regolith has a strong oxidizing capacity that can convert organic compounds into CO2 and probably water. While H2O2 was suggested originally for being the oxidizing agent responsible for the outcome of the Viking experiments, recent analyses of the martian regolith by the Phoenix lander and by consecutive missions point toward radiation-mediated decomposition products of perchlorate salts as the primary oxidant. In a series of experiments, we have shown that abrasion and triboelectric charging of basalt by simulated saltation could be an additional way of activating regolith. We have also shown that abraded basalt with a chemical composition close to that of martian regolith is toxic to several bacterial species and thus may affect the habitability of the martian surface. In the present study, we investigated the effect of the quantitatively most important minerals (olivine, augite, and plagioclase) and iron oxides (hematite, magnetite, and maghemite) on the survival of bacterial cells to elucidate whether a specific mineral that constitutes basalt is responsible for our observations. We observed that suspensions of iron-containing minerals olivine and augite in phosphate-buffered saline (1 × PBS) significantly reduce the number of surviving cells of our model organism Pseudomonas putida after 24 h of incubation. In contrast, the iron-free mineral plagioclase showed no effect. We also observed that suspending abraded olivine and augite in 1 × PBS led to a dramatic increase in pH compared to the pH of 1 × PBS alone. The sudden increase in pH caused by the presence of these minerals may partly explain the observed cytotoxicity. The cytotoxic effect of augite could be relieved when a strong buffer (20 × PBS) was used. In contrast, olivine, despite the stronger buffer, maintained its cytotoxicity. Iron oxides per se have no negative effect on the survival of our test organism. Overall, our experiments confirm the cytotoxicity of basalt and show that no single constituent mineral of the basalt can account for its toxicity. We could show that abraded iron-containing minerals (olivine and augite) change the pH of water when brought into suspension and thereby could affect the habitability of martian regolith.

Laboratory experiments mimicking the saltation process in a Mars-like atmosphere show that triboelectric processes lead to excitation and ionization of molecules and atoms in the gas phase [1]. (Saltation refers to the processes when the sand grains are lifted up into the air and suspended for a short distance before falling back to the surface with a parabolic trajectory). Spectral analysis of the triboluminescence accompanying the processes reveals excitation energies of at least 21 eV [1-2]. This result has inspired us to investigate if chemical changes are associated with the processes. Here we report month-long saltation mimicking experiments in a quartz ampoule with quartz grains (SiO2) in a methane (CH4) atmosphere. As the saltation proceeds, we observe a color change of the grains from white to reddish as seen in Fig. 1. Our experiments report laboratory results of photochemical process. We are not investigating saltation on planetary bodies. Figure 1. A: Quartz sample prior to the saltation experiment. B: Quartz sample after 340 days of a saltation in a quartz ampoule containing a methane atmosphere with an initial pressure of 561 mbar. The reddish grain-color looks like the color observed on the polar caps of Triton [3, 4] and Charon [5] as well as on the dwarf planet, Pluto [6]. The color of Charon is linked to cold-trapped methane rich volatiles [5]. The color on Triton and Pluto could be the result of photochemistry, leading to organic compounds formed in the atmosphere under exposure to UV radiation. The compounds deposit on the surface where they - along with potential gases, like N2 and CO - form tholin-like materials [7, 8]. The patches could also be formed by UV radiation of the surface material containing N2, CO and CH4. The excitation energies in the saltation experiments (at least 21 eV [1]) are similar to the energy of the hard UV radiation reaching the planetary bodies suggesting that analysis of the saltation produced reddish material could lead to insight into the reddish patches on these bodies. Our saltation experiments suggest an alternative way of forming tholins on planets with a methane-containing atmosphere and a solid surface. We study the reddish material with X-ray photoelectron spectroscopy (XPS), reflection spectroscopy and solid-state Raman spectroscopy. In addition, electron structure calculations give some insight into the complex chemistry. Experiments and calculations indicate the observations of color change can be explained as a coating of the quartz grains by polydiene polymers [9]. Calculated potential minima of a model for a polydiene with 10 C-atoms anchored to a quartz grain. A: quartz grain with 20 Si-atoms. Color code: red = O, steel = Si, green = C, and white = H. References [1] J. Thøgersen, et al., Light on windy nights on Mars: A study of saltation-mediated ionization of argon in a Mars-like atmosphere. Icarus 332, 14-18 (2019). [2] M. A. Lieberman, and A. J. Lichtenberg, (2005). Principles of plasma discharges and materials processing (2nd ed.). Hoboken, N.J.: Wiley-Interscience. 546. ISBN 978-0471005773. OCLCZZ 59760348. [3] D. F. Strobel, et al., The photochemistry of methane in the atmosphere of Triton, Geophys. Res. Lett. 17(10), 1729-1732 (1990). [4] W. M. Grundy, et al., Spectroscopy of Pluto and Triton at 3–4 Microns: Possible evidence for wide distribution of nonvolatile solids, Astron. J. 124, 2273–2278 (2002). [5] W. M. Grundy, et al., The formation of Charon’s red poles from seasonally cold-trapped volatiles. Nature 539, 65-68 (2016). [6] S. A. Stern, et al., The Pluto system: Initial results from its exploration by New Horizons. Science 350, aad1815 (2015). [7] C. Sagan, and B. Khare, Tholins: organic chemistry of interstellar grains and gas, Nature 277, 102-107 (1979). [8] G. D. McDonald, et al., Chemical investigation of Titan and Triton tholins. Icarus,. 108(1), 137–145 (1994). [9] P. Nørnberg, et al., Methane as a reddish coating agent. Icarus 382, 115023 (2022)

Experiments in quartz ampoules that simulate the saltation of quartz grains in a methane atmosphere show that the solid phase acquires a reddish color, reminiscent of the color observed on Triton, Pluto, and Charon. Reflection spectroscopy of the coated grains show a wide, continuous absorption spectrum peaking at near-UV wavelengths, in line with the reddish color. X-ray photoelectron spectroscopy indicates the grains are coated with a substance containing C-C and C-O bonds, and estimates the average thickness of the surface layer to 2.3 angstrom. Solid state Raman measurements of the coating shows a transition at 1540 cm(-1). A model is proposed to describe these measurements. The model is a polydiene, anchored to the quartz surface. Electron structure calculations show that a polydiene with around 8 CH units reproduces the measurements. AFM-IR experiments support this result. Our findings suggest a pathway for synthesis of complex molecules with C = C bonds on planets and moons with a solid surface and a methane-containing atmosphere.

AstrobiologyVol. 22, No. 9 News & ViewsSpore Survival During Abrasive Saltation on Mars: A Reply to the Comment by Minns et al.Ebbe Norskov Bak, Mikkel Bregnhøj, Per Nørnberg, Svend J. Knak Jensen, Jan Thøgersen, and Kai FinsterEbbe Norskov BakDepartment of Biology, Microbiology section, Aarhus University, Aarhus, Denmark.Search for more papers by this author, Mikkel BregnhøjDepartment of Biology, Microbiology section, Aarhus University, Aarhus, Denmark.Department of Chemistry, Aarhus University, Aarhus, Denmark.Search for more papers by this author, Per NørnbergDepartment of Biology, Microbiology section, Aarhus University, Aarhus, Denmark.Search for more papers by this author, Svend J. Knak JensenDepartment of Chemistry, Aarhus University, Aarhus, Denmark.Search for more papers by this author, Jan ThøgersenDepartment of Chemistry, Aarhus University, Aarhus, Denmark.Search for more papers by this author, and Kai FinsterAddress correspondence to: Kai Finster, Department of Biology, Microbiology section, Ny Munkegade 114–116, Aarhus University, DK-8000 Aarhus C, Denmark E-mail Address: Kai.Finster@bio.au.dkDepartment of Biology, Microbiology section, Aarhus University, Aarhus, Denmark.Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Aarhus, Denmark.Search for more papers by this authorPublished Online:5 Sep 2022https://doi.org/10.1089/ast.2022.0085AboutSectionsView articleView Full TextPDF/EPUB Permissions & CitationsPermissionsDownload CitationsTrack CitationsAdd to favorites Back To Publication ShareShare onFacebookTwitterLinked InRedditEmail View article"Spore Survival During Abrasive Saltation on Mars: A Reply to the Comment by Minns et al.." Astrobiology, 22(9), pp. 1032–1033FiguresReferencesRelatedDetails Volume 22Issue 9Sep 2022 InformationCopyright 2022, Mary Ann Liebert, Inc., publishersTo cite this article:Ebbe Norskov Bak, Mikkel Bregnhøj, Per Nørnberg, Svend J. Knak Jensen, Jan Thøgersen, and Kai Finster.Spore Survival During Abrasive Saltation on Mars: A Reply to the Comment by Minns et al..Astrobiology.Sep 2022.1032-1033.http://doi.org/10.1089/ast.2022.0085Published in Volume: 22 Issue 9: September 5, 2022Online Ahead of Print:August 10, 2022PDF download

Arctic permafrost soils store substantial reserves of organic matter (OM) from which microbial transformation contributes significantly to greenhouse gas emissions of CH4 and CO2. However, many younger sediments exposed by glacier retreat and sea level change in fjord landscapes lack significant organic carbon resources, so their capacity to promote greenhouse gas emissions is unclear. We therefore studied the effects of increased temperatures (4°C and 21°C) and OM on rates of Fe(III) reduction, CO2 production, and methanogenesis in three different Holocene sedimentary units from a single site within the former marine limit of Adventdalen, Svalbard. Higher temperature and OM addition generally stimulated CH4 production and CO2 production and an increase in Bacteria and Archaea abundance in all units, whereas an equal stimulation of Fe(II) production by OM amendment and an increase in temperature to 21°C was only observed in a diamicton. We observed an accumulation of Fe(II) in beach and delta deposits as well but saw no stimulating effect of additional OM or increased temperature. Interestingly, we observed a small but significant production of CH4 in all units despite the presence of large reservoirs of Fe(III), sulfate, and nitrate, indicating either the availability of substrates that are primarily used by methanogens or a tight physical coupling between fermentation and methanogenesis by direct electron transfer. Our study clearly illustrates a significant challenge that comes with the large heterogeneity on a narrow spatial scale that one encounters when studying soils that have complex histories.

Abstract The iconic Viking Landers that landed on Mars in 1976 demonstrated that the Martian surface is an extreme place, dominated by high UV fluxes and regolith chemistry capable of oxidizing organic molecules. From follow-on missions, we have learned that Mars was much warmer and wetter in its early history, and even some areas of Mars (such as crater lakes, possibly with sustained hydrothermal activity) were habitable places (e.g. Grotzinger et al. (2014). Science (New York, N.Y.) 343; Mangold et al. (2021). Science (New York, N.Y.). However, based on the Viking results we have learnt that the search for life and its remains is challenged by abiotic breakdown and alteration of organic material. In particular, the harsh radiation climate at the Martian surface that directly and indirectly could degrade organics has been held accountable for the lack of organics in the Martian regolith. Recent work simulating wind-driven erosion of basalts under Mars-like conditions has shown that this process, comparable to UV- and ionizing radiation, produces reactive compounds, kills microbes and removes methane from the atmosphere. and thereby could equally jeopardize the success of life-seeking missions to Mars. In this review, we summarize and discuss previous work on the role of physical and chemical mechanisms that affect the persistence of organics, and their consequences for the detection of life and/or its signatures in the Martian regolith and in the atmosphere.

A quartz ampoule with quartz grains is mechanically activated in a dry air-like atmosphere with 0.5 % of one of the major greenhouse gases CO2, CH4, and N2O. The grains rub against each other and the walls of the ampoule during activation, leading to triboelectric charging and erosion. IR spectroscopy shows the greenhouse gases disappear during activation. After activation, the ampoule rests for five days. IR spectra recorded after this period show no reappearance of the greenhouse gases.

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.

The increasing number of missions to Mars also increases the risk of forward contamination. Consequently there is a need for effective protocols to ensure efficient protection of the Martian environment against terrestrial microbiota. Despite the fact of constructing sophisticated clean rooms for spacecraft assembly a 100 % avoidance of contamination appears to be impossible. Recent surveys of these facilities have identified a significant number of microbes belonging to a variety of taxonomic groups that survive the harsh conditions of clean rooms. These microbes may have a strong contamination potential, which needs to be investigate to apply efficient decontamination treatments. In this study we propose a series of tests to evaluate the potential of clean room contaminants to survive the different steps involved in forward contamination. We used Staphylococcus xylosus as model organism to illustrate the different types of stress that potential contaminants will be subjected to on their way from the spacecraft onto the surface of Mars. Staphylococcus xylosus is associated with human skin and commonly found in clean rooms and could therefore contaminate the spacecraft as a result of human activity during the assembling process. The path the cell will take from the surface of the spacecraft onto the surface of Mars was split into steps representing different stresses that include desiccation, freezing, aeolian transport in a Martian-like atmosphere at Martian atmospheric pressure, and UV radiation climate. We assessed the surviving fraction of the cellular population after each step by determining the integrated metabolic activity of the survivor population by measuring their oxygen consumption rate. The largest fraction of the starting culture (around 70 %) was killed during desiccation, while freezing, Martian vacuum and short-term UV radiation only had a minor additional effect on the survivability of Staphylococcus xylosus. The study also included a simulation of atmospheric transport on Martian dust, which did not significantly alter the metabolic potential of the cells. The high survival potential of skin microbes, which are not among the most robust isolates, clearly underlines the necessity for efficient decontamination protocols and of adequate planetary protection measures. Thus we propose a series of tests to be included into the description of isolates from spacecraft assembly clean rooms in order to assess the forward contamination potential of the specific isolate and to categorize the risk level according to the organisms survival potential. We are aware that the tests that we propose do not exhaust the types of challenges that the microbes would meet on their way and therefore the series of tests is open to being extended.

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.

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.

The habitability of Mars is determined by the physical and chemical environment. The effect of low water availability, temperature, low atmospheric pressure and strong UV radiation has been extensively studied in relation to the survival of microorganisms. In addition to these stress factors, it was recently found that silicates exposed to simulated saltation in a Mars-like atmosphere can lead to a production of reactive oxygen species. Here, we have investigated the stress effect induced by quartz and basalt abraded in Mars-like atmospheres by examining the survivability of the three microbial model organisms Pseudomonas putida, Bacillus subtilis, and Deinococcus radiodurans upon exposure to the abraded silicates. We found that abraded basalt that had not been in contact with oxygen after abrasion killed more than 99% of the vegetative cells while endospores were largely unaffected. Exposure of the basalt samples to oxygen after abrasion led to a significant reduction in the stress effect. Abraded quartz was generally less toxic than abraded basalt. We suggest that the stress effect of abraded silicates may be caused by a production of reactive oxygen species and enhanced by transition metal ions in the basalt leading to hydroxyl radicals through Fenton-like reactions. The low survivability of the usually highly resistant D. radiodurans indicates that the effect of abraded silicates, as is ubiquitous on the Martian surface, would limit the habitability of Mars as well as the risk of forward contamination. Furthermore, the reactivity of abraded silicates could have implications for future manned missions, although the lower effect of abraded silicates exposed to oxygen suggests that the effects would be reduced in human habitats.

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.