Surfaces Of Planetary Bodies Research Articles

Sublimation and infrared spectral properties of ammonium cyanide

The ammonium ion (NH4+) has been suggested to be present in interstellar ices and has been observed on the surfaces of planetary bodies using infrared (IR) spectroscopy as the primary means of identification. Evidence for several ammonium salts has also been found in the dust and surface ices of comet 67P/Churyumov-Gerasimenko. Here we present a laboratory study of ammonium cyanide (NH4CN) and report on several properties of this compound, measured with higher accuracy than in previous reports, including its IR band strengths and optical constants for use in quantifying its abundance in interstellar and planetary ices. We also report the first measurements since 1882 of NH4CN vapor pressures, sublimation fluxes, and sublimation enthalpy measured at temperatures relevant to subliming cometary ices (134–155 K). The density and refractive index of NH4CN at 125 K and the sublimation enthalpy and vapor pressures of NH3 at ~100 K are also reported.

Automatic crater shape retrieval using unsupervised and semi-supervised systems

Impact craters are depressions formed due to impacts on the surface of planetary bodies. Recent deep learning-based crater detection methods assume craters as circular-shaped without much attention to extracting craters’ shape and morphology. Craters’ shape information (i.e., instance segmentation map for craters) can be helpful for many advanced analyses including crater formation and surface characteristics. However, publicly available ground truth catalogs for the lunar surface do not contain crater shape annotations and are also challenged by the missing craters problem. We attempt to solve these challenges by proposing a novel estimation and refinement-based approach using a combination of unsupervised and semi-supervised systems. Our method consists of (a) learning estimated crater segmentation (ECS) maps by a novel adaptive rim estimation algorithm (unsupervised system) using side information, (b) refining ECS by a cascade of Mask region-based convolutional neural networks (R-CNNs) to obtain refined crater segmentation (RCS) maps (semi-supervised system), and (c) combining RCS followed by predicting a highly accurate crater segmentation map. In the absence of any publicly available catalog for crater shape annotations, we conducted a ranking-based user study to compare against the state-of-the-art. The proposed method outperforms by achieving the best ranking for 63.53% crater images as compared to 9.67% for state-of-the-art. Further, the extracted shapes of the craters are utilized to improve the estimate of the craters’ diameter, depth, and other morphological factors to be made publicly available: https://drive.google.com/drive/folders/1ghBf2FXNIJUEQkAM2GjLZNiIXKEhZMEB?usp=sharing.

Electrostatic Repulsion of Dust from Planetary Surfaces

Surfaces of planetary bodies can have strong electric fields, subjecting conductive grains to repulsive electrostatic forces. This has been proposed as a mechanism to eject grains from the ground. To quantify this process, we study millimeter-sized basalt aggregates consisting of micrometer constituents exposed to an electric field in drop-tower experiments. The dust aggregates acquire high charges on subsecond timescales while sticking to the electrodes according to the field polarity. Charging at the electrodes results in a repulsive (lifting) force and continues until repulsion overcomes adhesion and particles are lifted, moving toward the opposite electrode. Some aggregates remain attached, which is consistent with a maximum charge limit being reached, providing an electrostatic force too small to counteract adhesion. All observations are in agreement with a model of moderately conductive grains with a small but varying number of adhesive contacts to the electrodes. This supports the idea that on planetary surfaces with atmospheres, electrostatic repulsion can significantly contribute to airborne dust and sand, i.e., decrease the threshold wind speed that is required for saltation and increase the particle flux as suggested before.

Visible and near-InfraRed (VNIR) reflectance of silicate glasses: Characterization of a featureless spectrum and implications for planetary geology

Silicate glasses represent a major component in volcanic products, both in pyroclastic deposits and lavas. To date, their spectral characteristics are not thoroughly investigated in the context of their characterization as possible analogues of planetary surfaces, mainly due to their lack of spectral features. Nevertheless, featureless VIS-NIR spectra for which it is only possible to retrieve relative parameters (slope, albedo) are commonly observed on the surface of planetary bodies, and volcanic structures are supposed to be widely present in all terrestrial planets within the Solar System. Therefore, the correct interpretation of their geochemical signature is important in the attempt to shed new light on the evolution of these planets, and detailed knowledge about the spectral response of silicate glasses is fundamental for such a purpose.In this study, experimental petrology techniques have been used to produce 15 silicate glasses having complex chemical composition corresponding to three of the most common magmatic series on planet Earth. These glasses have been investigated in the Visible and Near/Infrared range to observe and interpret the variation of slope, albedo, and spectral ratio R1.55/R0.8 as a function of chemical composition. We found that, despite the complexity of factors influencing the spectral response, a good correlation can be derived linking spectral parameters with both iron content and composite Silicium-Calcium-Iron-Magnesium content (SCFM parameter). Results presented in this work might represent the baseline for new research lines focused on deciphering the significance of silicate glasses in the context of planetary exploration, opening new windows to access information on planetary differentiation that cannot be obtained using only existing materials and methods.

A Model to Predict the Size of Regolith Clumps on Planetary Bodies

Abstract Prior investigations of the behavior of regolith on the surface of planetary bodies has considered the motion and interactions of individual grains. Recent work has shown the significance of cohesion in understanding the behavior of planetary regolith, especially on small, airless bodies. Surficial regolith grains may detach from a planetary body due to a variety of phenomena, including aeolian effects, spacecraft operations, micrometeoroid bombardment, and electrostatic lofting. It is well known in terrestrial powder handling that cohesive powders tend to form clumps. We present a theory for the size of regolith clumps that are likely to form and be easier to detach from a surface than their constituent grains, assuming monodisperse, spherical grains. The model predictions are significant for our interpretation of the surface of asteroids, as well as understanding a variety of phenomena on planetary bodies and designing of sampling spacecraft.

Ethane clathrate hydrate infrared signatures for solar system remote sensing

Hydrocarbons such as methane and ethane are present in many solar system objects, including comets, moons and planets. The interaction of these hydrocarbons with water ice at low temperatures could lead to the formation of inclusion compounds, such as clathrate hydrates (water based host cages trapping guest molecules), modifying their retention, stability and therefore evolution. The occurrence of clathrate hydrates on solar system surfaces could be established by remote sensing of their spectroscopic signatures. In this study, we measure and analyse ethane clathrate hydrate spectra recorded in the temperature range from 5.3 to 160 K, covering most of the temperature range of interest for solar system objects. Specific infrared band signatures are identified for the ethane encaged guest. We provide evidence that ethane clathrate hydrate outcrops can be detected by remote sensing on the surface of planetary bodies.

Review of nuclear techniques for planetary science

Spaceflight instruments that measure the energy and intensity of gamma rays and neutrons emitted by the surfaces of planetary bodies have been included in planetary science missions since 1966. These instruments use nuclear techniques to determine the elemental composition and related information about planetary surface and near-surface materials from the analysis of these gamma ray and neutron data. This paper provides a short review of these nuclear techniques as they have been used in current and past orbital and landed missions. A description of the nuclear instrumentation on many such missions is provided. Finally, descriptions of future missions that will employ gamma ray and neutron instruments will be presented.

Effects of Gamma and Electron Radiation on the Structural Integrity of Organic Molecules and Macromolecular Biomarkers Measured by Microarray Immunoassays and Their Astrobiological Implications.

High-energy ionizing radiation in the form of solar energetic particles and galactic cosmic rays is pervasive on the surface of planetary bodies with thin atmospheres or in space facilities for humans, and it may seriously affect the chemistry and the structure of organic and biological material. We used fluorescent microarray immunoassays to assess how different doses of electron and gamma radiations affect the stability of target compounds such as biological polymers and small molecules (haptens) conjugated to large proteins. The radiation effect was monitored by measuring the loss in the immunoidentification of the target due to an impaired ability of the antibodies for binding their corresponding irradiated and damaged epitopes (the part of the target molecule to which antibodies bind). Exposure to electron radiation alone was more damaging at low doses (1 kGy) than exposure to gamma radiation alone, but this effect was reversed at the highest radiation dose (500 kGy). Differences in the dose–effect immunoidentification patterns suggested that the amount (dose) and not the type of radiation was the main factor for the cumulative damage on the majority of the assayed molecules. Molecules irradiated with both types of radiation showed a response similar to that of the individual treatments at increasing radiation doses, although the pattern obtained with electrons only was the most similar. The calculated radiolysis constant did not show a unique pattern; it rather suggested a different behavior perhaps associated with the unique structure of each molecule. Although not strictly comparable with extraterrestrial conditions because the irradiations were performed under air and at room temperature, our results may contribute to understanding the effects of ionizing radiation on complex molecules and the search for biomarkers through bioaffinity-based systems in planetary exploration.

Unmelted cosmic metal particles in the Indian Ocean

AbstractFe‐Ni metal is a common constituent of most meteorites and is an indicator of the thermal history of the respective meteorites, it is a diagnostic tool to distinguish between groups/subgroups of meteorites. In spite of over a million micrometeorites collected from various domains, reports of pure metallic particles among micrometeorites have been extremely rare. We report here the finding of a variety of cosmic metal particles such as kamacite, plessite, taenite, and Fe‐Ni beads from deep‐sea sediments of the Indian Ocean, a majority of which have entered the Earth unaffected by frictional heating during atmospheric entry. Such particles are known as components of meteorites but have never been found as individual entities. Their compositions suggest precursors from a variety of meteorite groups, thus providing an insight into the metal fluxes on the Earth. Some particles have undergone heating and oxidation to different levels during entry developing features similar to I‐type cosmic spherules, suggesting atmospheric processing of individual kamacites/taenite grains as another hitherto unknown source for the I‐type spherules. The particles have undergone postdepositional aqueous alteration transforming finally into the serpentine mineral cronstedtite. Aqueous alteration products of kamacite reflect the local microenvironment, therefore they have the potential to provide information on the composition of water in the solar nebula, on the parent bodies or on surfaces of planetary bodies. Our observations suggest it would take sustained burial in water for tens of thousands of years under cold conditions for kamacites to alter to cronstedtite.

Interaction of aluminum projectiles with quartz sand in impact experiments: Formation of khatyrkite (CuAl2) and reduction of SiO2 to Si

We analyzed the interaction of spherical, 6.36-mm-diameter, Cu-bearing aluminum projectiles with quartz sand targets in hypervelocity impact experiments performed at NASA Ames Vertical Gun Range. Impact velocities and inferred peak shock pressures varied between 5.9 and 6.5km/s and ∼41 and 48GPa, respectively. Shocked particles (“impact melt particles”) coated with thin crusts of molten projectile material were recovered from the floors of the ca. 33-cm-diameter craters and the respective ejecta blankets. Through petrographic and chemical (optical microscopy, FE-EMPA, SEM-EDX, and XRF) analysis we show that these particles have a layered structure manifested in distinct layers of decreasing shock metamorphism. These can be characterized by the following physical and chemical reactions and alteration products: (i) complete melting and subsequent recrystallization of the projectile, forming a distinct crystallization texture in the fused metal crust; (ii) projectile–target mixing, involving a redox reaction between Cu-bearing Al alloy und SiO2, leading to formation of khatyrkite (CuAl2), Al2O3 melt, euhedral silicon crystals, and spherical droplets of silicon; (iii) melting of quartz to lechatelierite and formation of planar deformation features in relic quartz grains; and (iv) shock lithification of quartz grains with fracturing of grains, grain-boundary melting, planar deformation features, and complete loss of porosity. To our knowledge, this is the first report of khatyrkite formed experimentally in hypervelocity impact experiments. These results have implications for the understanding of a similar redox reaction between Al–Cu metal and siliceous impact melt recently postulated for the Khatyrka CV3 carbonaceous chondrite. Moreover, these results bear on the processes that lead to layers of regolith on the surfaces of planetary bodies without atmospheres, such as asteroids in the main belt (e.g., 4 Vesta), and on the Moon. Specifically, impacts of mm-sized projectiles at velocities between 4 and 6km/s into regolith-covered, asteroidal surfaces in the main belt should yield similar impact melt particles that feature a continuum of shock effects, i.e., partially to completely molten projectile remnants adhering to impact-melted regolith agglomerates, as well as projectile-contaminated impact melts and local shock melting along grain boundaries.

Remote-Sensing of Planetary Surface Using Infrared Spectroscopy

Infrared remote sensing provides essential knowledge about the current state of solid planetary surfaces. This allows addressing fundamental questions in comparative planetology. A large part of our knowledge about surface composition and structure of solid planetary surfaces is based on infrared remote sensing techniques. These techniques allow performing mineralogical composition analyses, measurement of surface temperature, thermal inertia, and photometric observation of surface regolith texture. The combination of geological mapping based on (visible light) imaging with infrared spectral data forms the basis for comparative studies in planetology. This paper will provide an overview of what we have learned about the surfaces of planetary bodies using infrared techniques from orbit and provide an outlook on future plans. Typically examples of the main types of instruments are described, and the interplay of disciplines like planetology, IR measuring techniques, and space flight engineering is demonstrated

Morphological study into the temperature dependence of solid ammonia under astrochemical conditions using vacuum ultraviolet and Fourier-transform infrared spectroscopy

The authors present the results of a morphological study of solid ammonia using both Fourier-transform infrared and vacuum ultraviolet (VUV) spectroscopy. Dramatic changes in the VUV and infrared spectra at temperatures between 65 and 85 K provide a deeper insight into the structure of ammonia ice particularly with the observation of an exciton transition at 194 nm (6.39 eV) in the VUV spectrum, revealing a structure that is composed of crystallites. A complementary structure is observed in the IR spectrum at 1100 cm(-1) which is assigned to the symmetric deformation of ammonia molecules at the surfaces of the crystallites. Such spectral signatures may be used to identify the environment within which the ammonia ice is formed and provide a new route for obtaining information on the physical and chemical conditions occurring within the interstellar medium, on the surfaces of planetary bodies, and in Kuiper belt objects.

Rivers in the Solar System: Water Is Not the Only Fluid Flow on Planetary Bodies

AbstractWater, either in liquid or ice form, is the most common fluid that forms channels and valleys on Earth. Lava flows also make channels. The responsible fluid is generally clear on Earth because the process of formation tends to be observable. Channels and valley landforms are widespread on surfaces of planetary bodies, but their formation processes are not normally observable in action. Therefore, planetary geologists rely on geomorphology and knowledge of the environment to infer the nature of the fluid that produced these features. A wide range of fluid flows, including water, lava of various compositions, carbon dioxide, and hydrocarbons, have been proposed for the genesis of channels and valleys on the Moon, Venus, Mars, Io, and Titan.

Big returns on small samples: Lessons learned from the analysis of small lunar samples and implications for the future scientific exploration of the Moon

Samples returned from the surface of planetary bodies are both complementary to orbital and in situ observations and provide a unique perspective for understanding the nature and evolution of that body. This unique perspective is based on the scale the sample is viewed (mm–Å), the ability to manipulate the sample, the capability to analyze the sample at high precision and accuracy, and the ability to significantly modify experiments as logic and technology dictates over an extended period of time (decades). Unlike the Apollo missions, robotic sample return missions in the next decade will result in the return of relatively small sample mass. Such robotically returned samples are scientifically more valuable if they can be placed within a planetary context through orbital observations and if information concerning planetary-scale processes and conditions can be extracted from them. Conversely, samples give remotely sensed data ground truth. That is, they act as a “calibration standard” for these data allowing a much enhanced global view to be constructed. The Moon is an example that illustrates how information can be extracted from small samples and then extended to planetary and solar system scales. Three examples from the Moon illustrate this point. First, multi-analytical and experimental studies of minute (10–500 μm) glass beads representing near-primary magmas provide constraints on the composition and condition of the lunar mantle, the style of early planetary differentiation, the history and character of early mantle dynamics and melting, and the isolation of the lunar mantle from late-stages of lunar accretion. Second, trace element analysis of individual mineral grains via ion microprobe and isotopic analysis of small rock fragments representing some of the oldest and youngest periods of lunar magmatism illustrate their usefulness for both fingerprinting distinct episodes of lunar magmatism and reconstructing the evolution of lunar magmatism. Third, mechanisms for primitive planetary mantles degassing and volatile transport on airless bodies can be understood by the analysis of volatile coatings on glass and mineral fragments in the lunar regolith. As many of our insights about the Moon are based on samples that primarily were collected within a limited lunar terrain, our understanding of the Moon is somewhat biased. Future scientifically strategic sampling targets are young mare basalts (Roris basalt in Oceanus Procellarum), far-side mare basalts (Mare Moscoviense), large pyroclastic deposits and potential mantle xenoliths (Aristarchus plateau, Rima Bode) major unsampled crustal lithologies outside the Procellarum KREEP terrane (central peak in Tsiolkovsky crater, South-pole Aitken basin), basin and crater melt sheets (South-pole Aitken basin, Giordano Bruno) and H deposits in permanently shaded areas (South-pole Aitken basin). Sampling these locations would further our understanding of processes at work during the early evolution of the terrestrial planets, provide a comprehensive history of endogenous (e.g., primary volcanic degassing) and exogenous (e.g., solar wind, galactic cosmic rays, volatiles from comets) volatile reservoirs and volatile transport and would provide unique historical information about events and processes that affected the entire inner solar system, a record obscured on the Earth and Mars.

Impacts in Precambrian Shields

One of the most fundamental geologic processes that have shaped the surfaces of the solar system's planetary bodies is the impact of solid bodies. It affects the surface of a planetary body not only by creating a visible crater, but also by modifying, locally and temporally, the crater subsurface and a wide area around the excavated crater. In particular, terrestrial impact structures are in the unique position of providing the only ground truth available for investigating the impact cratering process. The establishment of shock metamorphic effects on rocks as reliable criteria for assigning impact origins to terrestrial structures has led to the recognition of over 160 impact structures on Earth over the past 40 years. Investigation of these structures is fundamental for validating theoretical and experimental impact studies.

AI, Robotics and Automation in Space

Recently, AI, robotics and automation in space, referred to in a general term as ""space robotics"" in this paper, are playing increasingly more important roles for ground support, LEO satellites and planetary probes. In deep space missions, however, space robotics is a ""must"" due to the radio propagation delay and a poor communication link between the spacecraft and Earth. A typical example for robotics for planetary exploration is an autonomous rover that moves around on the surface of planetary bodies and conducts scientific investigations. A new infrastructure called ROBUST is proposed, which stands for ROBotized Unmanned Station. ROBUST is the space station that will be constructed, maintained and expanded by robotic technology completely without human presence in orbit.

Trace-element fractionation by impact-induced volatilization; SIMS study of lunar HASP samples

Impact is a dominant process acting on the surfaces of planetary bodies and is the major process that modifies the physical and chemical nature of planetary materials on atmosphere-free bodies once volcanic activity has ceased. Elements with relatively high volatilities are readily mobilized during impact. HASP (high alumina, silica poor) compositions are thought to be generated by impact-induced volatilization processes on the moon. The high Al/Si ratio of HASP is believed to be the result of preferential loss of SiO 2 relative to Al 2 O 3 . Here we report SIMS analyses for HASP glass beads and devitrified glasses from the Apollo 14 regolith to assess the behavior of Li, Be, B, REE, Sr, Y, and Zr during impact events. We compare the behavior of these trace elements to the behavior of major and minor elements analyzed by the electron microprobe. The HASP samples we studied fall into two compositional groups with one group apparently derived from KREEPy lunar lithologies and the other from anorthosite. The KREEPy HASP beads have an estimated mass loss of 28% compared to their KREEPy protolith. We estimate that 44% of SiO 2 and 35% of FeO were lost during impact-induced volatilization. The mass loss estimate for the anorthositic protolith to produce anorthositic HASP is more uncertain because of the uncertainty of the protolith composition. However, an estimate of approximately 25% appears reasonable with 38% loss of silica. Clearly, impact processes, in the early stages of planetary evolution, are important in the modification of geochemical signatures, and ordinarily geochemically coherent elements may be decoupled because of different volatilities.