Extraterrestrial Environments Research Articles

Non-Deterministic Factors Affect Competition Between Thermophilic Autotrophs from Deep-Sea Hydrothermal Vents

Hydrothermal vents provide windows into the rocky subseafloor on Earth and serve as terrestrial analog sites for extraterrestrial environments. By studying patterns of community assembly in hydrothermal vents and using geochemical models, we can better understand how the deep-sea biosphere contributes to local and global biogeochemical cycling and gather valuable information about how similar communities may arise on Earth and beyond Earth. One prevailing thought is that vent microbial community assembly is driven by deterministic factors such as the thermodynamic favorability of redox reactions. We hypothesized that subsurface microbial communities may also be significantly influenced by other factors, such as differential cell yields, varying optimal growth temperatures, and stochasticity. At Axial Seamount in the Pacific Ocean, H2-consuming methanogens of the genera Methanocaldococcus (Topt 82°C) and Methanothermococcus (Topt 65°C) and H2-consuming sulfur reducers of the genus Desulfurobacterium (Topt 72°C) are the most abundant autotrophs that grow optimally at or above 65°C (Fortunato et al. 2017). At one low-temperature hydrothermal vent site, Marker 113, methanogens are the predominant thermophilic autotrophs while at another site, Marker 33, thermophilic autotrophic sulfur reducers predominate. There is no apparent geochemical or thermodynamic explanation for the differences in community composition. In this study, we performed a series of co-culture competition experiments using Methanocaldococcus jannaschii, Methanothermococcus thermolithotrophicus, and Desulfurobacterium thermolithotrophum HR11 as representative methanogens and sulfur reducers common to hydrothermal vents to explain the variations in community composition between thermophilic autotrophs. M. jannaschii increases its cell yield (cells produced per mole of CH4 produced) when grown on very low H2 concentrations as part of a growth rate-growth yield tradeoff (Topçuoğlu et al. 2019). This increase in cell yield could provide methanogens with a competitive growth advantage over H2-consuming sulfur reducers, who otherwise catalyze a more thermodynamically favorable growth reaction. Competition co-culture experiments were conducted between M. jannaschii and D. thermolithotrophum at 72°C and between M. thermolithotrophicus and D. thermolithotrophum at 65°C, both at 1:1 ratios and initial aqueous H2 concentrations of 1.2 mM (high H2) and 85 μM (low H2) to determine the effects of temperature and H2 availability on autotroph competition. For both methanogens, the growth rate, maximum cell concentration, and total CH4 produced decreased when they were grown in co-culture, at low H2, or both relative to monocultures grown with high H2. The methanogen cell yields generally increased in co-culture and at low H2. At both experimental temperatures, the growth rate of D. thermolithotrophum remained unchanged in co-culture and at low H2 relative to monocultures but the maximum cell concentration decreased in co-culture relative to monocultures at both H2 concentrations. However, at low H2, both in mono- and co-culture, there was no detectable H2S produced by the sulfur reducer suggesting a significant shift in growth yield. At both temperatures and H2 concentrations, the sulfur reducer reached higher cell concentrations than the methanogens. Stochasticity or vent fluid chemistry could lead to early colonization of a vent by methanogens followed by niche exclusion of autotrophic sulfur reducers due to a numerical advantage of the methanogens. Therefore, competitive co-culture experiments were run as before at high H2 with varying initial methanogen:sulfur reducer ratios. At 72°C, D. thermolithotrophum reached the same maximum cell concentration and produced the same amount of H2S in monoculture and co-culture even when the methanogens initially outnumbered the sulfur reducer up to 10,000-fold. M. jannaschii reached a lower maximum cell concentration and produced less CH4 in all co-cultures relative to growth in monoculture. At 65°C, D. thermolithotrophum reached the same maximum cell concentrations and produced the same amount of H2S in monoculture and co-culture when the methanogens initially outnumbered the sulfur reducers up to 100-fold. However, when the methanogens initially outnumbered the sulfur reducers 1,000-fold, M. thermolithotrophicus grew as well as in monoculture and the maximum cell concentration and amount of H2S produced by D. thermolithotrophum was significantly lower than in monoculture and the other co-culture conditions. In conclusion, both methanogens and sulfur reducers shift their redox reactions away from CH4 and H2S production, respectively, and towards biomass production when H2 is limiting. This should be accounted for in thermodynamic predictive models. Furthermore, a combination of growth temperatures lower than the optimum of sulfur reducers and high initial methanogen cell concentrations relative to sulfur reducers can lead to a long-term predominance of methanogens over autotrophic sulfur reducers in vent environments through niche exclusion.

Athermalization of Optical System with Large Field of View for Image Navigation

Image navigation sensor is one of the most important sensing means for human to explore the extraterrestrial space environment, and optical system is a key component of image navigation sensor, directly determines the amount of information perceived. The optical system requirements of image navigation sensors are gradually developing towards large field of view and miniaturization. The fisheye lens is the first choice for large field of view imaging by selecting the appropriate optical structure, without adding other additional components, and has the advantages of small size and strong perception energy. However, as the image surface illuminance of fisheye lens will decrease sharply with the increase of the field of view, the change of temperature will also degrade the imaging quality of the system, and strong stray light sources such as the sun will easily enter the field of view, which will greatly affect the perception ability of the system. Because of this, effective design of these systems is quite difficult. In this paper, a reverse-telephoto structure was used for large-field imaging, and the degradation of imaging quality caused by temperature changes was eliminated by selecting appropriate optical and mechanical materials. Designed with a focal length of 6.7mm, an F number of 3.6, a viewing angle of 130°, a working band of 0.45μm to 0.65μm, an after work distance of 7mm, a total system length≤60mm, we tested our system in a -40°C to +60°C temperature range and measured the image quality. Through simulation analysis, the system in the whole field of view within our spot diagrams was≤5.5μm, optical transfer function was greater than 0.2 at 90lp/mm, and no vignetting occurred. Furthermore, the imaging illumination of the edge field of view was 0.72 times that of the center field of view, the f – tan (θ) relative distortion value of the center field of view was≤2.3%, and the f – θ relative distortion value of the edge field of view was≤2.7%. Compared to normal temperatures, the optical transfer function changes at -20°C and +40°C were 0.02 and 0.01, respectively. Thus, the system displayed the characteristics of excellent image quality, small size, high energy utilization rate and good non-thermal performance.

Construction management in space: explore solution space of optimal schedule and cost estimate

Multi-planetary life is one of humanity's audacious dreams. A key challenge towards achieving such a space mission is the design and construction of space habitats, for instance, on Mars. This paper presents a virtual space construction decision framework (SCDF) prototype developed and tested to address the question: "How can space construction project partners make informed decisions and leverage new construction methods and cutting-edge technologies that are developed and transform the AEC terrestrial industry?" We consider six practical and theoretical points of departure reflecting knowledge and technology and their application towards developing SCDF: General Contractor Workflow; BIM; Generative Scheduling and Construction Schedule Optimization; Construction Robotics; 3D Printing; Virtual Reality (VR) and Visualization. SCDF development applied virtual design and construction (VDC) to model - simulate - optimize - visualize - validate a space construction project by exploring the solution space in the context of extra-terrestrial construction environments from concept design to construction completion in the virtual environment before any mission is launched. Results confirm that insights from terrestrial construction apply to extra-terrestrial construction and vice versa. These insights contribute to the six points of departure at three levels: 1. The SCDF; 2. Extensions to existing technology platforms; 3. New approaches and methods.

Functional Meta-Analysis of the Proteomic Responses of Arabidopsis Seedlings to the Spaceflight Environment Reveals Multi-Dimensional Sources of Variability across Spaceflight Experiments.

The human quest for sustainable habitation of extraterrestrial environments necessitates a robust understanding of life's adaptability to the unique conditions of spaceflight. This study provides a comprehensive proteomic dissection of the Arabidopsis plant's responses to the spaceflight environment through a meta-analysis of proteomics data from four separate spaceflight experiments conducted on the International Space Station (ISS) in different hardware configurations. Raw proteomics LC/MS spectra were analyzed for differential expression in MaxQuant and Perseus software. The analysis of dissimilarities among the datasets reveals the multidimensional nature of plant proteomic responses to spaceflight, impacted by variables such as spaceflight hardware, seedling age, lighting conditions, and proteomic quantification techniques. By contrasting datasets that varied in light exposure, we elucidated proteins involved in photomorphogenesis and skotomorphogenesis in plant spaceflight responses. Additionally, with data from an onboard 1 g control experiment, we isolated proteins that specifically respond to the microgravity environment and those that respond to other spaceflight conditions. This study identified proteins and associated metabolic pathways that are consistently impacted across the datasets. Notably, these shared proteins were associated with critical metabolic functions, including carbon metabolism, glycolysis, gluconeogenesis, and amino acid biosynthesis, underscoring their potential significance in Arabidopsis' spaceflight adaptation mechanisms and informing strategies for successful space farming.

UWB and MB-OFDM for Lunar Rover Navigation and Communication

This paper presents a comprehensive study of ultra-wideband (UWB) and multi-band orthogonal frequency-division multiplexing (MB-OFDM) technologies for lunar rover navigation and communication in challenging terrains. Lunar missions pose unique challenges, such as signal propagation in the lunar environment, terrain elevation, and rover movement constraints. To address these challenges, we propose a hybrid communication and navigation system that leverages UWB technology for high-precision positioning and MB-OFDM for robust and high-throughput communication. We develop a realistic simulation framework that incorporates terrain elevation, obstacles, and rover movement constraints, along with a simple fading model for communication. Simulation results demonstrate the effectiveness of the proposed system in navigating lunar rovers to their target locations while maintaining reliable communication links with a lunar lander. A novel approach based on game theory for rover navigation is also presented. The study provides valuable insights into the design and optimization of communication and navigation systems for future lunar missions, paving the way for seamless integration of advanced terrestrial technologies in extraterrestrial environments.

Benchmarking and Simulation of Solid-Oxide Steam Electrolysis for Propellant Production in a Vacuum Chamber-Simulated Lunar Environment

NASA and other space agencies have prioritized the development of in-situ resource utilization (ISRU) technology for producing critical materials such as propellants in space. Electrolysis to split water found in lunar, asteroid, and Martian environments provides a pathway for liquid H2 and O2 production, but the challenges of deploying such technology in extraterrestrial environments put an extreme emphasis on minimizing specific energy (measured in kWhelec/kgH2) and system specific mass (system kg/(kgH2/h)). High-temperature, solid oxide electrolysis cell (SOEC) systems have the potential to achieve lower specific energy than conventional liquid-phase alkaline and polymer electrolyte membrane (PEM) electrolysis systems, but this requires efficient thermal integration and minimization of balance of plant loads in order to take advantage of the lower electrolysis voltages for steam (vs. liquid H2O). The high operating temperatures of SOECs, however, require significant system mass for steam generators, heat exchangers for recuperation, and insulation of the electrolysis stack, particularly for space applications where ambient temperatures may be extremely low.This NASA-sponsored collaboration between OxEon Energy and Colorado School of Mines explored the feasibility of a lunar-based SOEC system, which was modeled and demonstrated at the lab-scale by operating a breadboard system, consisting of a SOEC stack and associated balance of plant BOP) in a cryogenic vacuum chamber in order to simulate a lunar environment. The combined »2.5-kWelec SOEC stack and BOP achieved a specific energy < 50 kWhelec/kgH2 at an H2 production rate of > 0.075 kgH2/h operating in the cryo-vacuum chamber.This study has benchmarked system-level models of the lab-scale SOEC stack based on doped-zirconia electrolytes fabricated at OxEon and designed to operate near thermoneutral voltage (1.28 V/cell) at 800°C. The stack BOP includes a steam generator, an oil-free scroll compressor, cathode and anode exhaust recuperators, and a H2 dryer, which uses cold incoming liquid water feeds to cool the cathode exhaust and condense most of the excess H2O in the H2 product stream out. Operation of this demonstration system provides a basis for designing scaled-up lunar fuel production systems of 40 kgH2/h. The success of the lab-scale tests in terms of thermal integration and the benchmarked models suggest a pathway to such a full-scale SOEC system that can achieve < 46 kWhelec/kgH2 with much lower specific mass.Both the modeling and the lab-scale demonstration tests revealed that system specific energy was most sensitive to stack steam utilization, and that achieving < 50 kWhelec/kgH2 required stack steam utilization > 75%. In addition, effective thermal integration that limited the electrical heating primarily to steam generation is critical to minimizing the SOEC-system BOP loads. The stack was shown to run reliably at steam utilizations > 90% with a single pass feed. Efforts will be presented on how to simulate such high utilization at larger scales for full lunar deployment. Additional testing of the lab-scale system in larger cryo-vacuum chambers at NASA during 2023 will allow for further confirmation of thermal management strategies to ensure reliable SOEC operation for lunar production of H2/O2 propellants.

The probabilistic nature of dune collisions in 2D

Abstract. Dunes are bedforms of different size and shape, appearing throughout aeolian, subaqueous and extraterrestrial environments. Collisions between dunes drive dune field evolution, and are a direct result of interacting dunes of different heights, travelling at different speeds. We perform 2D cellular automaton simulations of collisions between dune pairs migrating in a steady flow. Modelled collisions can result in either ejection, where dunes exchange mass before separating, or downstream- or upstream-dominant coalescence (merging of dunes). For each of these three elementary types of interaction, we identify the mass exchange mechanism and the distinctive intermediate morphologies. Surprisingly, we show that the collision outcome depends probabilistically on the initial dune area ratio r and can be described by a narrow sigmoidal function centred on r=1/2. Finally, we compare our simulations with laboratory experiments of dune collisions, finding good agreement concerning the intermediate morphology and the collision outcome. Our results can motivate further observational or experimental studies that validate our probabilistic collision predictions and fully determine the controls on the coalescence–ejection transition.

Influence of irradiation energy and damage coefficient on performance of CH3NH3PI3 photocell

An organic–inorganic hybrid perovskite as a light-absorbing layer has become a key material in many laminated-structures used in photon sensing devices. Some of these devices are referred to as Organic–inorganic hybrid perovskite (OIHP)-based devices. In recent days, OIHP applications have sky-rocketed in the world of flexible photo-electronics. Due to the higher radiation tolerances, OIHP-based solar cells have been recommended for terrestrial applications which is an application that require low fabrication costs that combines lightweight materials. However, it has been noticed that when it is used in extra-terrestrial environments, these photo cell devices experience premature failures once they interact with fast multispectral radiations in terrestrial spaces. Due to these premature failures, a similar solar cell from an (OIHP)-based perovskite material of methyl ammonium lead iodide (CH3NH3PI3) was investigated as an observer layer under a multi-spectral simulated illumination. After simulation, data for the expected photocurrent flowing through junction components on a glass substrate coated with a thin layer of Titanium dioxide (TiO 2) film was obtained. The influence of energy of irradiation on damage coefficients, current density, photovoltage and I–V characteristic profile curves were determined and investigated. Some general common macroscopic parameters for photon sensing were analyzed on three dimensions (3D) to determining the minority charge carriers and their induced photo-voltages with respect to junction recombination velocities. The obtained computed macroscopic parameters were incorporated into the Quite Universal Circuit Simulator software for simulation. It was established that damage coefficient influenced the I–V curve and an accumulation of charge carriers magnifies the probability of plasmons initiating degradation of the absorber layer. The atoms in the CH3NH3Pl3 crystal lattice system uniformly recoils at resonance and transport the maximum charge carriers across the P-N junction capable of creating a significant damage concentrated within a few micrometer ranges on the surface that may even extend between 0.39 to about 1.01 micrometers in size. This paper therefore evaluates the influence of irradiation energy and damage coefficient in a hybrid CH3NH3PI3 mono-facet crystal structure on exposure to multi-spectral illumination at varied irradiation energies.

Leakage of surfactants in greywater: Environmental impact, mitigation, and their circular economy

Globally, grey wastewater management is potently mismanaged in developing countries, which is a threat to circular economy. In order to address two significant challenges, water scarcity and water management, this literature study intends to offer insightful information on the environmental impact and mitigation of surfactants present in greywater. The present review focuses on the recent advancements made in eliminating surfactants from greywater through various techniques such as adsorption, ultrafiltration, biodegradation, and bio-membrane separation. Despite these advancements, the complete elimination of surfactants remains a substantial and unresolved challenge. To address this widening gap in wastewater management, the present study also emphasizes the urgent implementation for alternative strategies through the reuse of both treated and untreated greywater. Additionally, it emphasizes the specific influence of surfactants on plant growth and productivity. It explores the potential of greywater as a nutrient source for crop cultivation in both terrestrial and extraterrestrial environments, using techniques such as aeroponics. It further delves into the aspects associated with the establishment of an aeroponic module for crop cultivation using GW, highlighting the importance of optimizing module design by considering various operational parameters, with a focus on surfactant-related factors such as concentration and type. However, the adoption of safe greywater reuse in irrigation and cultivation continues to face many challenges and criticism, which have been further elucidated in this review.

Structural synthesis of the reconfigurable legged mobile lander for strong geometry-physical interaction with extraterrestrial environment

To design the engineering prototype of reconfigurable legged mobile lander (ReLML) for strong geometry-physical interaction with extraterrestrial environment, this paper proposes a tailored structural synthesis methodology unifying kinematic geometry and statics. Compared with our preceding works, three inbuilt operation modes are first integrated: adjusting mode is a totally new mode defined as three rotations (3R) with a strong geometrical adaptation to hostile terrain; landing mode is redefined as two rotations one translation (2R1T), inherits Chang'E lander to survive from strong impact interaction; roving mode turns into the other 2R1T motion for good motion/force interactivity. The interaction characteristics (motion, force, energy) between ReLML and environment are extracted to derive output finite motions and instantaneous wrenches of leg end-effector, following the principles of optimal force system equilibrium and work efficiency. The motion and force synergistic syntheses of metamorphic limb and joint are implemented to design and assemble mechanical generators. The ReLML can serve the alien base construction and adjustable launch bracket. The unified structural synthesis methodology of kinematic geometry and statics is universal and effective for designing parallel mechanisms and reconfigurable mechanisms, especially for strong physical interaction scenarios.

Estimation of the mass fraction and distribution of ice in a lunar regolith simulant from seismic velocity

The exploration of ice distribution on the Moon and in other extraterrestrial environments has recently accelerated because of the growing interest in the distribution of ice in, and its acquisition from, the Moon's polar regions. Understanding of the relationship between the mass fraction of ice and the velocities of P-wave and S-wave is expected to allow ice amounts to be estimated from seismic exploration results. To clarify this relationship, we numerically investigated the effect of ice on elastic wave velocities using a digital rock physics approach for regolith with heterogeneous pore geometries. We digitized a lunar regolith simulant and modeled ice distribution in its pore spaces. Numerical simulations employing a finite element method were then performed to calculate the P-wave and S-wave velocities of the regolith simulant while varying the ice particle size and the mass fraction of ice. The results demonstrate that the characteristics of the velocity changes with increases in the mass fraction of ice differ depending on the particle size distribution of the ice. For the same mass fraction of ice, P-wave and S-wave velocities are higher for smaller ice clusters (up to 1.75 times for P-wave velocity and 1.76 times for S-wave velocity). Using the numerical simulation results, we succeeded in developing an empirical equation for estimating the mass fraction of ice from P-wave and S-wave velocities. This equation should be useful for quantifying ice content from lunar seismic survey data.

Iodine-Biofortified Microgreens as High Nutraceutical Value Component of Space Mission Crew Diets and Candidate for Extraterrestrial Cultivation.

The success of Space missions and the efficacy of colonizing extraterrestrial environments depends on ensuring adequate nutrition for astronauts and autonomy from terrestrial resources. A balanced diet incorporating premium quality fresh foods, such as microgreens, is essential to the mental and physical well-being of mission crews. To improve the nutritional intake of astronaut meals, two levels of potassium iodide (KI; 4 µM and 8 µM) and an untreated control were assessed for iodine (I) biofortification, and overall nutraceutical profile of four microgreens: tatsoi (Brassica rapa L. subsp. narinosa), coriander (Coriandrum sativum L.), green basil, and purple basil (Ocimum basilicum L.). A dose-dependent increase in I was observed at 8 µM for all species, reaching concentrations of 200.73, 118.17, 93.97, and 82.70 mg kg-1 of dry weight, in tatsoi, coriander, purple basil, and green basil, respectively. Across species, I biofortification slightly reduced fresh yield (-7.98%) while increasing the antioxidant activity (ABTS, FRAP, and DPPH). LC-MS/MS Q extractive orbitrap analysis detected 10 phenolic acids and 23 flavonoids among microgreen species. The total concentration of phenolic acids increased (+28.5%) in purple basil at 8 µM KI, while total flavonoids in coriander increased by 23.22% and 34.46% in response to 4 and 8 µM KI, respectively. Both doses of KI increased the concentration of total polyphenols in all species by an average of 17.45%, compared to the control.

Houston, we have a problem…or do we? The trajectory of astrobioethics and Indigenous thought

AbstractBackgroundAt the 2022 meeting of the American Society for Bioethics and Medical Humanities, a new affinity group was formed: astrobioethics. This is the branch of bioethics for space exploration, extraterrestrial environments and possible extraterrestrial organisms. Bioethics has traditionally operated from Western/Global North dominated thought structures and it is difficult to introduce alternative frameworks. However, astrobioethics is forming and is primed to include alternative frameworks, such as pre-Columbian Indigenous American philosophy/ethics and Global South frameworks and knowledge.MethodsThe methods utilized include Indigenous research methodologies and standpoint, an overview of Indigenous American philosophy/ethics, and reflection on how this may impact astrobioethical considerations of space exploration.Discussion and ConclusionsIndigenous philosophies and ethics consider space exploration and its associated risks and impacts on potential extraterrestrial lifeforms, systems and environments. The nuances of using terms like ‘colonization’ are considered and the paper concludes by considering how Méxica philosophical concepts and the four main Indigenous pragmatic dimensions can interact with established bioethical principles to guide future space exploration.

Effects of chaotropic salts on global proteome stability in halophilic archaea: Implications for life signatures on Mars.

Halophilic archaea thriving in hypersaline environments, such as salt lakes, offer models for putative life in extraterrestrial brines such as those found on Mars. However, little is known about the effect of the chaotropic salts that could be found in such brines, such as MgCl2 , CaCl2 and (per)chlorate salts, on complex biological samples like cell lysates which could be expected to be more representative of biomarkers left behind putative extraterrestrial life forms. We used intrinsic fluorescence to study the salt dependence of proteomes extracted from five halophilic strains: Haloarcula marismortui, Halobacterium salinarum, Haloferax mediterranei, Halorubrum sodomense and Haloferax volcanii. These strains were isolated from Earth environments with different salt compositions. Among the five strains that were analysed, H. mediterranei stood out as a results of its high dependency on NaCl for its proteome stabilization. Interestingly, the results showed contrasting denaturation responses of the proteomes to chaotropic salts. In particular, the proteomes of strains that are most dependent or tolerant on MgCl2 for growth exhibited higher tolerance towards chaotropic salts that are abundant in terrestrial and Martian brines. These experiments bridge together global protein properties and environmental adaptation and help guide the search for protein-like biomarkers in extraterrestrial briny environments.

Safely advancing a spacefaring humanity with artificial intelligence

A “Space Renaissance” is underway. As our efforts to understand, utilize and settle space rapidly take new form, three distinct human-space interfaces are emerging, defined here as the “Earth-for-space,” “space-for-Earth” and “space-for-space” economies. Each engenders unprecedented opportunities, and artificial intelligence (AI) will play an essential role in facilitating innovative, accurate and responsive endeavors given the hostile, expansive and uncertain nature of extraterrestrial environments. However, the proliferation of, and reliance on, AI in this context is poised to aggravate existing threats and give rise to new risks, which are largely underappreciated, especially given the potential for great power competition and arms-race-type dynamics. Here, we examine possible beneficial applications of AI through the systematic prism of the three economies, including advancing the astronomical sciences, resource efficiency, technological innovation, telecommunications, Earth observation, planetary defense, mission strategy, human life support systems and artificial astronauts. Then we consider unintended and malicious risks arising from AI in space, which could have catastrophic consequences for life on Earth, space stations and space settlements. As a response to mitigate these risks, we call for urgent expansion of existing “responsible use of AI in space” frameworks to address “ethical limits” in both civilian and non-civilian space economy ventures, alongside national, bilateral and international cooperation to enforce mechanisms for robust, explainable, secure, accountable, fair and societally beneficial AI in space.

Planetary geoarchaeology as a new frontier in archaeological science: Evaluating site formation processes on Earth's Moon

AbstractOn October 4, 1957, Homo sapiens crossed a new threshold of technological innovation after constructing an artifact capable of entering Low Earth Orbit and effectively paving the way for a future of space exploration. This artifact was Sputnik 1, launched by the Soviet space program which triggered the “space race” of the mid‐20th century. Over the past 65 years, we have continued to explore and populate our solar system with rockets and spacecraft including satellites, probes, landers, and rovers. This expansion into our solar system has left traces of our presence on several planets including the Earth, Mars, Mercury, and Venus along with Earth's Moon, Titan, and several galaxy travelers in the form of asteroids and comets. Today, we have entered the realm of a new privatized and global space race, effectively a “new space race” or “new Space Age.” As we expand our material footprint into new extraterrestrial environments, there is a growing need to understand the types of unique site formation processes capable of altering, destroying, or preserving this rapidly increasing archaeological record known as space heritage. Such understandings are germane to the subdiscipline of geoarchaeology, that part of archaeology dedicated to studying the interaction between humans, cultural heritage, and environmental systems from a geoscience perspective. Closely aligned and partially overlapping with the subdisciplines of space archaeology, archaeological science, and planetary geology, we introduce a new subfield we call planetary geoarchaeology to open discussion about how geoarchaeologists can play a role in addressing current and future issues surrounding the preservation and management of space heritage. To demonstrate the potential of the subdiscipline, we focus on the current archaeological record of the Moon, describe lunar site formation processes, and discuss the implications for the current and future preservation of space heritage in the lunar setting. Planetary geoarchaeology can be applied to practically every type of extraterrestrial environment, provided humans have left behind a measurable record. We hope this paper will spur more research studying human–environment interaction in space.

Lunar active seismic profiler for investigating shallow substrates of the Moon and other extraterrestrial environments

To investigate the structures and properties of shallow material in extraterrestrial environments, we have developed a lunar active seismic profiler (LASP), which integrates active seismic sources and receivers in a short (~1 m) array that can be deployed on a rover. The small active source generates a chirp waveform that sweeps over a wide frequency range (20–250 Hz). The receivers are coupled to the ground by their own weight, but nevertheless deliver acceptable performance. We improve the signal-to-noise ratio of the seismic signal by stacking waveforms, enabling a minimal source to support the exploration of geological substrates. By processing shot gather of the LASP data, we calculated a dispersion curve of surface waves and obtained an accurate S-wave velocity profile from surface to 1 m depth. The results suggest that regions with even small amounts of subsurface ice (~0.5 wt%) can be identified in LASP results by their anomalously high S-wave velocity. Field experiments demonstrate that the LASP can support estimates of 3D S-wave velocity distributions and the identification of a buried geological boundary. The LASP also detected different degrees of compaction at the experimental site. If two rovers carry these profilers, or if a single rover combines one with a separately deployed receiver or active seismic source, seismic refraction and seismic reflection analyses can be conducted simultaneously in addition to surface wave analyses. These seismic surveys for longer-offset data achieve the exploration of deeper substrates in extraterrestrial settings such as the Moon, Mars, and other solid bodies.

Fungal-induced fossil biomineralization

Exceptional preservation of fossils has often been attributed to the actions of bacteria that aid in the preservation of soft tissues that normally decay rapidly. However, it is well known that fungi play a major role in organic matter decomposition, biogeochemical cycling of elements, and metal-mineral transformations in modern ecosystems. Although the fungal fossil record can be traced back over a billion years, there are only a few recorded examples of fungal roles in fossilization. In this research, we have carried out a detailed geobiological investigation on early Pleistocene hyena coprolites (fossilized dung) in an attempt to ascertain possible fungal involvement in their formation. Using an advanced microscopic and mineralogical approach, we found that numerous hydroxyapatite nanofibers (25-34nm on average), interwoven to form spheroidal structures, constituted the matrix of the coprolites in addition to food remains. These structures were found to be extremely similar in texture and mineral composition to biominerals produced during laboratory culture of a common saprophytic and geoactive fungus, Aspergillus niger, in the presence of a solid source of calcium (Ca) and phosphorus (P). This observation, and our other data obtained, strongly suggests that fungal metabolism can provide a mechanism that can result in fossil biomineralization, and we hypothesize, therefore, that this may have contributed to the formation of well-preserved fossils (Lagerstätten) in the geological record. The characteristic polycrystalline nanofibers may also have served as a potential biosignature for fungal life in early Earth and extraterrestrial environments.

Closing the Shell: Gas-Phase Solvation of Halides by 1,3-Butadiene.

Gas-phase solvation of halides by 1,3-butadiene has been studied via a combination of photoelectron spectroscopy and density functional theory. Photoelectron spectra for X- ⋯(C4 H6 )n (X=Cl, Br, I where n=1-3, 1-3 and 1-7 respectively) are presented. For all complexes, the calculated structures indicate that butadiene is bound in a bidentate fashion through hydrogen-bonding, with the chloride complex showing the greatest degree of stabilisation of the internal C-C rotation of cis-butadiene. In both Cl- and Br- complexes, the first solvation shell is shown to be at least from the vertical detachment energies (VDEs), however for I- , increases in the VDE may suggest a metastable, partially filled, first solvation shell for and a complete shell at . These results have implications for gas-phase clustering in atmospheric and extraterrestrial environments.

TRUSTS: A novel treadmill-based multifunctional testing system for performance evaluation of wheeled planetary exploration rover

This paper presents a novel treadmill-based multifunctional testing system (TRUSTS) to execute ground testing for wheeled planetary exploration rover (WPER) in both regular and extreme physical conditions before launching. The TRUSTS with specially-made components featuring compact structure and multifunctional testing items comprises a traction loading subsystem (TLS) and a treadmill-based resistance torque loading subsystem (TRTLS). The former offers the working modes including traction loading, position holding, and range limiting. The latter offers working modes including resistance torque loading and leader–follower tracking. By appropriately allocating the working modes of two subsystems, the TRUSTS is capable of conducting diverse testing items. The customized controllers for the TLS and the TRTLS are proposed to guarantee the operation performance of the TRUSTS in all testing items. Extensive experimental results on a Mars rover prototype in both regular and extreme physical conditions demonstrate that the devised TRUSTS could effectively executing trafficability and maneuverability as well as adaptability tests with reliable scenarios and satisfactory precisions of motion tracking and traction/torque loading, which makes the TRUSTS a favorable choice for comprehensive performance assessment of rover in simulant extraterrestrial environment.