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The extremophile bacterium Deinococcus radiodurans is characterized by its ability to survive and sustain its activity at high levels of radiation and is considered an organism that might survive in extraterrestrial environments. In the present work, we studied the combined effects of temperature and chlorine-containing salts, with focus on perchlorate salts which have been detected at high concentrations in Martian regolith, on D. radiodurans activity (CO2 production rates) and viability after incubation in liquid cultures for up to 30 days. Reduced CO2 production capacity and viability was observed at high perchlorate concentrations (up to 10% w/v) during incubation at 0 or 25 °C. Both the metabolic activity and viability were reduced as the perchlorate and chloride salt concentration increased and temperature decreased, and an interactive effect of temperature and salt concentration on the metabolic activity was found. These results indicate the ability of D. radiodurans to remain metabolically active and survive in low temperature environments rich in perchlorate. [ABSTRACT FROM AUTHOR]

The prospect of establishing extra-terrestrial habitats using in situ resource utilization (ISRU) constitutes a long-term goal of multiple space agencies around the world. In this work, we investigate furnace sintering as a potential route for making building blocks—termed synthetic space bricks—using in situ regolith material. By systematically evaluating sintering parameters using a numerical lattice model, coupled with experimental observations and post-sintering characterization, we propose a process protocol for two lunar simulants (lunar highland simulant (LHS-1) and lunar mare dust simulant (LMS-1)) and one Martian simulant (mars global simulant, MGS-1). The resulting bricks demonstrate compressive strengths of up to 45 MPa under uniaxial loading, depending on the simulant used. These strengths are much greater than those typically mandated for structural applications under reduced gravity. Taking recourse to classical ceramic sintering studies, we infer particle-level sintering mechanisms indirectly by measuring temporal evolution exponents of sample dimensions. For all three simulants, volume diffusion appears to be the primary mechanism for particle coalescence. Our results clearly make a strong case for the use of sintering as a potentially scalable method for consolidating regolith into brick-like structures for construction and load-bearing applications in extra-terrestrial settings. [ABSTRACT FROM AUTHOR]

For space missions to either the Moon or Mars, protecting mechanical moving parts from the abrasive effects of prevailing surface dust is crucial. This paper compares the abrasive effects of two lunar and two Martian simulant regoliths using special pin-on-disc tests on a stainless steel/polytetrafluoroethylene (PTFE) sealing material pair. Due to the regolith particles entering the contact zone, a three-body abrasion mechanism took place. We found that friction coefficients stabilised between 0.2 and 0.4 for all simulants. Wear curves, surface roughness measurements, and microscopic images all suggest a significantly lower abrasion effect of the Martian regoliths than that of the lunar ones. It applies not only to steel surfaces but also to the PTFE pins. The dominant abrasive micro-mechanism of the disc surface is micro-ploughing in the case of all tests, while the transformation of the counterface is mixed. The surface of pin material is plastically transformed through micro-ploughing, while the material is removed through micro-cutting due to the slide over hard soil particles. [ABSTRACT FROM AUTHOR]

This paper presents a theoretical analysis of the data on wave velocity measurements at small stresses presented in a companion paper describing the experimental results on a Martian regolith loose sandy simulant (Fontainebleau sand) of the soil at the InSight landing site on Mars (Elysium Planitia). Experimental data of wave velocities and Poisson's ratio are interpreted in the light of a granular contact mechanics theory and completed accounting for rugosity effects that are suspected to have stronger effects in sands under low stresses. The asperities of a grain of Fontainebleau sand were investigated through Atomic Force Microscopy, but larger asperities had to be adopted so as to better fit the model prediction with experimental data. A good agreement between the experimental data and the model predictions is obtained for stress above 10 kPa. Below 5 kPa, an area in which asperities are suspected to have a stronger influence, the model is not fully satisfactory, showing that further experimental and theoretical investigation is necessary in a stress zone particularly relevant to surface soils in planets, with probably enhanced effects of asperities on the intergrain contact mechanics. Plain Language Summary: To better understand seismic wave propagation at the surface of the InSight landing site on Mars, this paper presents a theoretical interpretation of the seismic wave velocities at low stress measured in a sand sample used as a Martian regolith simulant and presented in a companion paper. The theory is based on both a theoretical elastic model of a pack of smooth spheres of same diameter and approach accounting for the effects of local rugosity at the contact between sand grains (rugosity is supposed to have a stronger influence at the low stresses resulting from the smaller gravity on Mars). The sphere pack model shows that some slippage between grains is necessary to properly account for the radial deformation of a cylindrical sample subjected to an increase in axial stress (as described by an elastic parameter called the Poisson ratio). Accounting for rugosity effects allows a better prediction of the changes in wave velocity with respect to stress. The decrease in velocity under decreased stress is confirmed, but the rugosity parameter measured using an Atomic Force Microscope was under‐estimated, probably due to the over‐simplistic hypothesis of considering spheres. A proper prediction was obtained by fitting this parameter at a twice larger value. Key Points: A novel theory based on contact mechanics was proposed to calculate Vp and Vs of uniform granular materialsThe theory considers the roughness of the particles, the stress, the porosity of the granular assembly, and the properties of the grainsTheoretical results agree with experimental measurements on loose samples of Fontainebleau sand used as a Mars regolith simulant [ABSTRACT FROM AUTHOR]

• To date, geotechnical instrumentation has been absent from Mars missions. • The Perseverance rover's abrading bit has a similar form factor to a Bevameter. • We study the use of the abrading bit tool to perform soil strength measurements. An instrument for measuring the geotechnical properties of the Martian soil provides high-value science opportunities and high-priority mission-support capabilities that serve reconnaissance, science, and engineering. Such instrument can be used to characterize the terrain for drilling, landing, trafficability, and other surface operations. However, to date, instruments for measuring geotechnical properties have been absent from Mars exploration missions. This paper examines the use of the Mars 2020 Perseverance rover's abrading bit tool to perform regolith strength measurements. The Perseverance rover's abrading bit has a similar form factor to a Bevameter, a tool commonly used to collect engineering geotechnical data to assess terrain traversability. To demonstrate a methodology by which the abrading bit can be employed to characterize soil strength, a portable testbed that mimics the flight system is designed and built using commercial off-the-shelf components. A data-processing pipeline is developed to convert raw measurements to soil strength. Tests were performed on three characterized simulants with different mechanical properties. The results show that the abrading bit is capable of making shear and bearing strength measurements with quantified uncertainties and demonstrate, for the first time, the ability to perform controlled geotechnical analysis using a standard science instrument. [ABSTRACT FROM AUTHOR]

Cylindrical specimens of Martian and Lunar regolith simulants were molded using a simple salt water binder and sintered at various temperatures for comparing microstructure, mechanical properties and shrinkage. Material microstructure are reported using optical microscope and material testing is done using an MTS universal testing machine. A total of twenty samples were made for the Mars global simulant (MGS-1), and twenty more using Lunar mare simulant (LMS-1). The samples were split into groups of five and the sintering profiles were varied for each group. The specimens were fabricated via an injection molding method, designed to replicate typical masonary units manufactured via Binder Jetting Technique (BJT), an important additive manufacturing (AM) technique. Results show that for both the Martian and Lunar regolith that the optimal sintering temperature was somewhere between 1100°C and 1200°C. The compressive strength for both the Martian and Lunar masonary samples, that received optimal sintering conditions, was determined to be sufficient for construction of extraterrestrial structures. This work demonstrates the feasibility of implementing an accessible in-situ binder material, for either Martian or Lunar regolith, in order to construct extra-terrestrial masonary structures. The work provides a feasible path towards the direct implementation of BJT for the manufacturing of either Lunar or Martian masonary prisms. [ABSTRACT FROM AUTHOR]

In order to investigate the in‐space in situ resource utilization, directed energy deposition (DED)‐based additive manufacturing (AM) has been utilized to process Martian regolith—Ti6Al4V (Ti64) composites. Here we investigated the processability of depositing 5, 10, and 100 wt% of Martian regolith premixed with Ti6Al4V using laser‐based DED, analyzing the printed structure via X‐ray diffraction, Vicker's microhardness, scanning electron microscopic imaging, and wear characteristics utilizing an abrasive water jet cutter to simulate abrasive environments on the Martian surface. The results indicate that the surface roughness and hardness of the composites increase with respect to the Martian regolith' weight percentage due to in situ ceramic reinforcement. For instance, i5‐wt% addition of Martian regolith increased the Vicker's microhardness from 366 ± 6 HV0.2 for as‐printed Ti64 to 730 ± 27 HV0.2 while maintaining similar abrasive wear performance as Ti6Al4V. The results point toward laser‐based AM for fabricating Ti64—Martian regolith composites with comparable properties. The study also reveals promising results in limiting the mass burden for future space missions, resulting in cheaper and easier launches. [ABSTRACT FROM AUTHOR]

Martian regolith is one of the primary science objectives of Mars exploration missions. The Rover Penetrating Radar carried by Zhurong rover allows for high-resolution subsurface imaging and in-situ measurements of Martian regolith dielectric properties, which are crucial to advance our understanding of Martian geology and hydrological evolution. While earlier studies have derived dielectric constants for the shallow subsurface, further characterization of subsurface materials requires the determination of attenuation properties. In this study, we applied the centroid-frequency shift method to explore the attenuation property of the Martian regolith in the frequency domain. Lateral attenuation variation was analyzed in detail by integrating subsurface radargram and navigation terrain images. The results show that, within a depth of ∼4 m, the attenuation of radar signal for Zhurong subsurface material is equal to a loss tangent of 0.0079, with a standard deviation of 0.001. Based on the loss tangent value, dielectric permittivity and ground characterization, we preclude the possibility that the regolith is predominantly igneous materials. The lateral variation of the attenuation property could likely be attributed to changes in the proportion of duricrusts, which are heterogeneously distributed along the rover traverse. Our findings offer valuable information for understanding the Martian regolith and its evolution, serving as a important reference for future Mars sample return missions. • We used the centroid-frequency shift method to estimate the loss tangent of Martian regolith. • We compared the estimated results using CFS method and time-domain based method. • The regolith's origin was analyzed based on dielectric properties and ground characterization. • The heterogeneity of regolith was attributed to the distribution of subsurface rocks. [ABSTRACT FROM AUTHOR]

By leveraging the capabilities of construction 3D printing, building structures in harsh extraterrestrial environments is conceivable. Sulfur concrete is a waterless construction material that offers great potential to replace Portland cement concrete (PCC) in extraterrestrial construction. The shape stability of 3D printed Martian sulfur-regolith concrete (SRC) was found to benefit from a lower substrate layer temperature. However, this comes at the cost of flexural strength, resulting in up to 53% strength loss. The printed SRC specimens demonstrated a significantly faster strength development rate (gaining about 85% of the ultimate strength after only 12 h) compared to the printed PCC. The printed SRC specimens also outperformed the PCC specimens in vacuum conditions at higher temperatures. Furthermore, modifying the SRC materials with Dicyclopentadiene resulted in up to 44% strength increase and minimized the sublimation rate of the printed specimens in vacuum, especially at an elevated temperature. • Sulfur concrete made with high-fidelity Martian simulant was successfully printed • The substrate layer temperature influences shape stability and flexural strength • Modifying the sulfur-regolith concrete with DCPD enhanced its properties • Sulfur concrete showed superior mechanical strength compared to regular concrete • Sulfur concrete showed superior vacuum resilience compared to regular concrete [ABSTRACT FROM AUTHOR]

Perchlorate (ClO4-) is globally enriched in Martian regolith at levels commonly toxic to plants. Consequently, perchlorate in Martian regolith presents an obstacle to developing agriculture on Mars. Here, we assess the effect of perchlorate at different concentrations on plant growth and germination, as well as metal release in a simulated Gusev Crater regolith and generic potting soil. The presence of perchlorate was uniformly detrimental to plant growth regardless of growing medium. Plants in potting soil were able to germinate in 1 wt.% perchlorate; however, these plants showed restricted growth and decreased leaf area and biomass. Some plants were able to germinate in regolith simulant without perchlorate; however, they showed reduced growth. In Martian regolith simulant, the presence of perchlorate prevented germination across all plant treatments. Soil column flow-through experiments of perchlorate-containing Martian regolith simulant and potting soil were unable to completely remove perchlorate despite its high solubility. Additionally, perchlorate present in the simulant increased metal/phosphorous release, which may also affect plant growth and biochemistry. Our results support that perchlorate may modify metal availability to such an extent that, even with the successful removal of perchlorate, Martian regolith may continue to be toxic to plant life. Overall, our study demonstrates that the presence of perchlorate in Martian regolith provides a significant challenge in its use as an agricultural substrate and that further steps, such as restricted metal availability and nutrient enrichment, are necessary to make it a viable growing substrate. [ABSTRACT FROM AUTHOR]

NASA's current mandate is to land humans on Mars by 2033. Here, we demonstrate an approach to produce ultrapure H2 and O2 from liquid-phase Martian regolithic brine at ~-36 °C. Utilizing a Pb2Ru2O7-δ pyrochlore O2-evolution electrocatalyst and a Pt/C H2-evolution electrocatalyst, we demonstrate a brine electrolyzer with >25x the O2 production rate of the Mars Oxygen In Situ Resource Utilization Experiment (MOXIE) from NASA's Mars 2020 mission for the same input power under Martian terrestrial conditions. Given the Phoenix lander's observation of an active water cycle on Mars and the extensive presence of perchlorate salts that depress water's freezing point to ~-60 °C, our approach provides a unique pathway to life-support and fuel production for future human missions to Mars. [ABSTRACT FROM AUTHOR]

Perchlorate (ClO4−) is globally enriched in Martian regolith at levels commonly toxic to plants. Consequently, perchlorate in Martian regolith presents an obstacle to developing agriculture on Mars. Here, we assess the effect of perchlorate at different concentrations on plant growth and germination, as well as metal release in a simulated Gusev Crater regolith and generic potting soil. The presence of perchlorate was uniformly detrimental to plant growth regardless of growing medium. Plants in potting soil were able to germinate in 1 wt.% perchlorate; however, these plants showed restricted growth and decreased leaf area and biomass. Some plants were able to germinate in regolith simulant without perchlorate; however, they showed reduced growth. In Martian regolith simulant, the presence of perchlorate prevented germination across all plant treatments. Soil column flow-through experiments of perchlorate-containing Martian regolith simulant and potting soil were unable to completely remove perchlorate despite its high solubility. Additionally, perchlorate present in the simulant increased metal/phosphorous release, which may also affect plant growth and biochemistry. Our results support that perchlorate may modify metal availability to such an extent that, even with the successful removal of perchlorate, Martian regolith may continue to be toxic to plant life. Overall, our study demonstrates that the presence of perchlorate in Martian regolith provides a significant challenge in its use as an agricultural substrate and that further steps, such as restricted metal availability and nutrient enrichment, are necessary to make it a viable growing substrate.

The current study discovers that uniaxial compression under ambient condition can directly cause strong bonding in ultra-dry montmorillonite, which is attributed to the secondary molecular interaction other than hydrogen bonding. The strength of so-processed material is sensitive to the lateral confinement condition of loading. Similar compaction pressure produces equally strong solids between quasi-static and impact loading modes. Gas permeability of the compacted solids is comparable to those of dense rocks. These findings shed light on the study of Martian regolith and in-situ resource utilization. [ABSTRACT FROM AUTHOR]

Martian regolith and Earth’s basaltoid samples have been investigated by means of Mössbauer spectroscopy. The identification of the same minerals: olivine, pyroxene, magnetite, hematite and confrontation of the Fe3 + /Fe2 + , Fe3 + /Fetot, Fe2 + /Fetot ratios are presented. Co-existence of olivine and hematite in Martian regolith, absent in presented by authors terrestrial samples has been tentatively explained. [ABSTRACT FROM AUTHOR]

Abstract: We studied the dehydration behavior of iron(II) sulfate heptahydrate (FeSO4·7H2O) as part of NASA''s in situ resource utilization program for the recovery of water on Mars. We examined the effect of the variables important in using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The temperatures at which waters of hydration are removed and the enthalpy values for the various dehydration steps were measured using DSC. For the dehydration of FeSO4·7H2O, a particle size <45μm, a heating rate of 2.5°C/min, an open DSC pan, and a horizontal baseline correction produced experimental values for the enthalpies of each dehydration step and overall dehydration of 145.7, 180.4, 64.8 and 390.9kJ/mol, respectively, which were in −8.8, 1.2, 3.35 and −2.47%, respectively, of those estimated from standard heats of formation and literature heat capacities. Generally, lower heating rates and smaller particle sizes are better for resolving the dehydration steps. The horizontal baseline corrections give better results when there is little or no peak overlap. As discussed above, proper selection of DSC and TGA operating parameters and baseline analysis technique is required to obtain accurate thermal results. [Copyright &y& Elsevier]

The cost of transporting raw materials into Space is prohibitive - potentially US$2 million for a single brick to be shipped to the Moon. This means that the future of extraterrestrial construction rests on the development of technologies that are able to employ in-situ materials, such as lunar dust. Guest-Editor Neil Leach is a NASA Innovative Advanced Concepts Fellow, collaborating with colleagues from the University of Southern California (USC) on a research project developing a robotic fabrication technology capable of printing structures on the Moon and Mars. Here he describes the inroads that NASA and European Space Agency (ESA) consortia are independently making into 3D-printed fabrication technologies. [ABSTRACT FROM AUTHOR]