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The current contribution presents a new sinkage sensor specified for an unmanned ground vehicle to find the exact sinkage zone of a wheel interacting with the soil particles. This sensor will be wrapped around the wheel, and consequently, contact analog outputs will be used in soil deposition and bulldozing effect prediction. Furthermore, the new sensor will be used for a novel soil flow calculation estimating the total mass variation of the control volume of soil particles beneath the wheel. Accordingly, the spiral model simulating the displacement of the particle is implemented to calculate the soil deposition.
The theory of lithopanspermia proposes the natural exchange of organisms between solar system bodies through meteorites. The focus of this theory comprises three distinct stages: planetary ejection, interplanetary transit and planetary entry. However, it is debatable whether organisms transported within the ejecta can survive all three stages. If the conjecture is granted, that life can indeed be safely transmitted from one world to another, then it is not only a topic pertaining to planetary science but also biological sciences. Hence, these stages are only the first three factors of the equation. The other factors for successful lithopanspermia are the quality, quantity and evolutionary strategy of the transmitted organisms. When expanding into new environments, invading organisms often do not survive in the first attempt and usually require several attempts through propagule pressure to obtain a foothold. There is a crucial difference between this terrestrial situation and the one brought about by lithopanspermia. While invasive species on Earth repeatedly enters a new habitat, a species pragmatically arrives on another solar system body only once; thus, an all-or-nothing response will be in effect. The species must survive in the first attempt, which limits the probability of survival. In addition, evolution sets a boundary through the existence of an inverse proportionality between the exchanges of life between two worlds, thus further restricting the probability of survival. However, terrestrial populations often encounter unpredictable and variable environmental conditions, which in turn necessitates an evolutionary response. Thus, one evolutionary mode in particular, bet hedging, is the evolutionary strategy that best smooth out this inverse proportionality. This is achieved by generating diversity even among a colony of genetically identical organisms. This variability in individual risk-taking increases the probability of survival and allows organisms to colonize more diverse environments. The present analysis to understand conditions relevant to a bacterial colony arriving in a new planetary environment provides a bridge between the theory of bet hedging, invasive range expansion and planetary science.
I originally penned this essay in the summer of 2018, stimulated by a Twitter exchange I had with Elon Musk, itself triggered by the SpaceX CEO’s previously announced decision to colonize Mars. This led me to wonder if this visionary had given any thought to what sort of government he would set up on the Red Planet and if he already had a team of social scientists working on the problem or whether he was just going to wing it when they got there. Surely not, but what source for research would a team of social engineers (let’s call them) working at SpaceX (or NASA, since it too plans to send people to Mars in the coming decades) access? There are no working models. Or are there? There are. Since it is Earthlings going to Mars, experiments in governance on the Blue Planet are a useful resource for lessons on how to govern the Red Planet. This essay, originally published in Quillette, is my modest contribution to future Martians on what they should take with them when they slip the surly bonds of earth.
During the Noachian period, 4.1-3.7 Gys ago, the Martian environment was moderately similar to the one on present Earth. Liquid water was widespread in a neutral environment, volcanic activity and heat flow more vigorous, and atmospheric pressure and temperature were higher than today. These conditions may have favoured the spread of life on the surface of Mars. The recognition that different planets and moons share rocky material cast in space by meteoroid impact entails that life creation is not necessary for each single planetary body, but could travel through the Solar system on board of rock fragments. Studies conducted on the past forms of Martian life have already highlighted possible positive matches with microbialite-like structures, referable to the geo-environmental conditions in the Noachian and Hesperian. However, by necessity, these studies are on predominantly micro and meso-scopic scale structures and doubts arise as to their attribution to the biogenic world. We suggest that in the identification of Martian life, we are currently in a position similar to the one of Kalkowsky who in 1908, based solely on morphological and sedimentological arguments, hypothesized the (now accepted) view of the biotic origin of stromatolites. Our analysis of thousands of images from Spirit, Opportunity and Curiosity has provided a selection of images of ring-shaped, domal and coniform macrostructures that resemble terrestrial microbialites such as the ring-shaped stromatolites of Lake Thetis, and stacked cones reminiscent of the group of terrestrial Conophyton. Notably, the latter were detected by Curiosity in the mudstone known as ‘Sheepbed’, the same outcrop where past organic molecules have been detected and where the occurrence of microbial-induced sedimentary structures (MISS) and of many more microbialitic micro, meso and macrostructures has already been hypothesized. Some of the structures discussed in this work are so complex that alternative biological hypotheses can be formulated as possible algae. Alternate, non-abiotic explanations are examined but we find difficult to explain some of such structures in the context of normal sedimentary processes, both syngenetic or epigenetic.
Any space program involving long-term human missions will have to cope with serious risks to human health and life. Because currently available countermeasures are insufficient in the long term, there is a need for new, more radical solutions. One possibility is a program of human enhancement for future deep space mission astronauts. This paper discusses the challenges for long-term human missions of a space environment, opening the possibility of serious consideration of human enhancement and a fully automated space exploration, based on highly advanced AI. The author argues that for such projects, there are strong reasons to consider human enhancement, including gene editing of germ line and somatic cells, as a moral duty.
Stand-off Raman spectroscopy is emerging as a critical new tool for planetary exploration. Mounted on a rover, a stand-off Raman system can be used to rapidly identify areas of interest for subsequent, synergistic investigations with other stand-off or close-up (arm-mounted) instruments; survey broad areas and perform reconnaissance tasks from a fixed location; and increase the efficiency of mission operations where targets of interest are in areas that are too hard to access for a rover. Not surprisingly, NASA’s next Mars mission will fly a stand-off Raman system as part of the SuperCam instrument package. This chapter reviews two stand-off Raman systems that paved the way for the development of new technologies and instrument architectures for robotic stand-off planetary exploration using Raman spectroscopy, including the SuperCam instrument suite.
The Alpha-Particle X-ray Spectrometer (APXS) is part of the scientific payload of all four Mars rovers to date. It determines the chemical composition of rocks and soils using X-ray spectroscopy during irradiation with alpha particles and X-rays from 244 cm. All elements heavier than fluorine can be detected by their characteristic X-ray lines. Typically, 16 elements are quantified for each martian sample. An additional 10 trace elements can be quantified for unusual high abundances. The APXS has provided compositional data at 4 landing sites, analyzing more than 1000 samples along a combined traverse of ~70 km. The diverse composition of soils and rocks has provided insights about martian geology and environmental conditions. Soils at all landing sites are similar and basaltic, but enriched in S, Cl, and Zn, likely from volcanic exhalations. A variety of igneous rocks have been documented. High sulfur concentrations in Ca sulfate veins, ferric sulfate subsurface soil deposits, and the extensive Burns formation with ~30% sulfate indicate extensive interactions with acidic fluids in the past. APXS bulk geochemistry complements mineralogy data and images and delivers crucial constraints for the interpretation of other investigations, like ground truth for orbital remote sensing instruments or comparison with martian meteorites.
The first Laser-Induced Breakdown Spectroscopy (LIBS) instrument for extraterrestrial applications is part of the ChemCam instrument suite onboard the Curiosity Mars rover. ChemCam may be used in a number of operational modes depending on the science questions of interest, including active (with laser) and passive (spectrometers only) modes, and there is important synergy between ChemCam and other payload instruments. Notable discoveries made with ChemCam LIBS data include the characterization of hydrogen in rocks and soils, discovery of boron on Mars, and characterization of other trace elements (Li, F, Rb, Sr, Ba) that were previously never or rarely quantified on Mars, depth-dependent chemical trends on rock surfaces, and a much broader range of bulk-rock chemical compositions than was previously recognized, including highly evolved igneous rocks. In addition to ChemCam, another LIBS instrument is slated to fly to Mars on the Mars 2020 rover mission as part of the combined Raman-LIBS SuperCam instrument.
Thermal infrared data collected by the Thermal Emission Spectrometer (TES) and Thermal Emission Imaging System (THEMIS) instruments have significantly impacted the understanding of martian surface mineralogy. Spatial/temporal variations in igneous lithologies; the discovery of quartz, carbonates, and chlorides; and the widespread identification of amorphous, silica-enriched materials reveal a planet that has experienced a diversity of primary and secondary geo-logic processes including igneous crustal evolution, regional sedimentation, aqueous alteration, and glacial/periglacial activity.
Multispectral imaging – the acquisition of spatially contiguous imaging data in a modest number (~3–16) of spectral bandpasses – has proven to be a powerful technique for augmenting panchromatic imaging observations on Mars focused on geologic and/or atmospheric context. Specifically, multispectral imaging using modern digital CCD photodetectors and narrowband filters in the 400–1100 nm wavelength region on the Mars Pathfinder, Mars Exploration Rover, Phoenix, and Mars Science Laboratory missions has provided new information on the composition and mineralogy of fine-grained regolith components (dust, soils, sand, spherules, coatings), rocky surface regions (cobbles, pebbles, boulders, outcrops, and fracture-filling veins), meteorites, and airborne dust and other aerosols. Here we review recent scientific results from Mars surface-based multispectral imaging investigations, including the ways that these observations have been used in concert with other kinds of measurements to enhance the overall scientific return from Mars surface missions.
Spectral modeling techniques have been developed for the analysis of planetary surfaces using large thermal infrared (TIR) spacecraft datasets. These techniques can be applied to three main spectral analysis problems: (1) correction for atmospheric effects for the recovery of surface emissivity; (2) isolation and separation of surface spectral endmembers for the characterization of surface mineralogy; and (3) determination of surface anisothermality for the retrieval of surface physical properties and correction for thermal emission in near-infrared spectral data. These modeling techniques have been extensively applied to martian and lunar spacecraft datasets, forming a basis for the retrieval of surface physical and compositional properties.
This chapter provides a brief review of missions using X-ray, gamma-ray, and neutron spectroscopy to determine the chemical composition of planetary surfaces. This chapter presents the history of planetary radiation measurements, including significant discoveries. Summary tables with links to the archived data provide a resource for readers interested in working in this field. Upcoming missions and possible future directions are described.
An ever-increasing number of laboratory facilities are enabling in situ spectral reflectance measurements of materials under conditions relevant to all the bodies in the Solar System, from Mercury to Pluto and beyond. Results derived from these facilities demonstrate that exposure of different materials to various planetary surface conditions can provide insights into the endogenic and exogenic processes that operate to modify their surface spectra, and their relative importance. Temperature, surface atmospheric pressure, atmospheric composition, radiation environment, and exposure to the space environment have all been shown to measurably affect reflectance and emittance spectra of a wide range of materials. Planetary surfaces are dynamic environments, and as our ability to reproduce a wider range of planetary surface conditions improves, so will our ability to better determine the surface composition of these bodies, and by extension, their geologic history.
A Miniature Thermal Emission Spectrometer (Mini-TES), based on a Michelson interferometer and Cassegrain telescope, was carried by the Spirit rover in Gusev crater and Opportunity rover at Meridiani Planum to determine the bulk mineralogy of surface materials. Spectra from the plains of Gusev demonstrate the ubiquity of olivine-rich basaltic rocks, with additional examples lofted into the adjacent Columbia Hills by meteoroid impacts. Hundreds of rocks observed with mini-TES in the Columbia Hills display spectral characteristics of variable alteration intensity, but likely with very little water involved. Rare exceptions include a tephra deposit cemented by Mg–Fe carbonates and nodular opaline silica rocks, likely indicative of a hot spring/geyser environment. Opportunity’s mini-TES confirmed orbital identification of crystalline hematite at Meridiani Planum and spectral characteristics indicative of a transition from a precursor goethite phase. The sedimentary bedrock that hosts the hematite has spectral features consistent with Al-rich opaline silica, Mg-, Ca-, and Fe-bearing sulfates, plagioclase feldspar, and nontronite. Rare rocks at both sites are recognizable as iron meteorites from their infrared reflective properties.
Visible to short-wave infrared (VSWIR, 0.4–5.0 µm) reflectance spectroscopy is a powerful tool to identify and map mineral groups on the martian surface. The Mars Express/OMEGA and Mars Reconnaissance Orbiter/CRISM instruments have characterized more than 30 mineral groups, revolutionizing previous understanding of martian crustal composition and the role of water in altering it. Analyses of these spectral images revealed the primary structure of the crust to be dominated by basalt, over a deep layer of segregated pyroxene- and olivine-rich plutons, with sparse feldspar-rich, differentiated intrusions. Martian volatile-bearing environments have evolved through four phases: the pre-Noachian to early Noachian period when alteration by liquid water occurred near the surface and deep in the subsurface, in chemically neutral to alkaline environments that formed hydrous silicates and carbonates; the middle to late Noachian period when liquid water was widely present at the surface forming valley networks, lacustrine deposits, and clay-rich pedogenic horizons; the early Hesperian to early Amazonian period during which water became increasingly acidic and saline, forming deposits rich in sulfate salts, chlorides, and hydrated silica; and the Amazonian period when surface water has existed predominantly as ice, with only localized reaction with regolith and briny flow on the surface.
Radar has proven to be a powerful tool in planetary exploration. Most of the major solid bodies of the Solar System have been observed with radar, either from Earth or from spacecraft. Planetary radar studies are reviewed in this chapter, with information on the various techniques of radar remote sensing provided along with key results. Recent radar results are emphasized. Concluding remarks are provided on future directions in planetary radar remote sensing.
Mössbauer instruments were included on the Mars Exploration Rover (MER) Mission to determine the mineralogic composition, diversity, and oxidation state of Fe-bearing igneous materials and alteration products. A total of 16 Fe-bearing phases (consistent with bulk-sample chemistry) were identified, including Fe associated with rock-forming minerals (olivine, pyroxene, magnetite, ilmenite, and chromite), Fe3+-bearing oxyhydroxides (nanophase ferric oxide, hematite, and goethite), sulfates (jarosite and an unassigned Fe3+ sulfate phase), and Fe2+ carbonate. Igneous rock types ranged from basalts to ultramafic rocks at Gusev crater. Jarosite-hematite bedrock was pervasive at Meridiani Planum, and concretions winnowed from the outcrop were mineralogically hematite. Because their structures contain hydroxyl, goethite, and jarosite provide mineralogic evidence for aqueous processes on Mars, and jarosite and Fe3+ sulfate are evidence for acid-sulfate processes at both Gusev crater and Meridiani Planum. A population of rocks on the Meridiani Planum outcrop was identified as iron and stony meteorites by the presence of Fe metal (kamacite) and the sulfide troilite. The MER mission demonstrates that Mössbauer spectrometers landed on any Fe-bearing planetary surface provide first-order information on igneous provinces, alteration state, and alteration style and provide well-constrained criteria for sample selection on planetary sample-return missions including planets, moons, and asteroids.