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The near-Earth asteroid 162173 Ryugu, the target of the Hayabusa2 sample-return mission, is thought to be a primitive carbonaceous object. We report reflectance spectra of Ryugu’s surface acquired with the Near-Infrared Spectrometer (NIRS3) on Hayabusa2, to provide direct measurements of the surface composition and geological context for the returned samples. A weak, narrow absorption feature centered at 2.72 micrometers was detected across the entire observed surface, indicating that hydroxyl (OH)–bearing minerals are ubiquitous there. The intensity of the OH feature and low albedo are similar to thermally and/or shock-metamorphosed carbonaceous chondrite meteorites. There are few variations in the OH-band position, which is consistent with Ryugu being a compositionally homogeneous rubble-pile object generated from impact fragments of an undifferentiated aqueously altered parent body. [ABSTRACT FROM AUTHOR]

The article talks about stewardship in a Biblical perspective, linking it with the modern livestock production practices. Topics discussed include the changes to agricultural practices in history; the cultural mandate for humanity's responsibilities in Christianity; and the importance of honoring God in agricultural practices.

High spatial and spectral resolution reflectance data acquired by the Mars Reconnaissance Orbiter Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) instrument reveal the presence of H2O- and SiOH-bearing phases on the Martian surface. The spectra are most consistent with opaline silica and glass altered to various degrees, confirming predictions based on geochemical experiments and models that amorphous silica should be a common weathering product of the basaltic Martian crust. These materials are associated with hydrated Fe sulfates, including H3O-bearing jarosite, and are found in finely stratified deposits exposed on the floor of and on the plains surrounding the Valles Marineris canyon system. Stratigraphic relationships place the formation age of these deposits in the late Hesperian or possibly the Amazonian, implying that aqueous alteration continued to be an important and regionally extensive process on Mars during that time. [ABSTRACT FROM AUTHOR]

Introduction: Primitive C-complex asteroids have been found to exhibit absorption features in the 2.7-4 μm wavelength region in their reflectance spectra (referred to as the "3 μm feature") that are diagnostic of OH and/or H2O in the form of hydrated minerals [e.g., 1-3]. The potential diagnostic capacity of the 3 μm absorption feature in determining the extent of aqueous alteration has motivated workers to propose taxonomical schemes to organize meteorites and asteroids based on the wavelength position and shape of the absorption feature [4]. However, these measurements and others like them were performed on powdered meteorites, which by their nature are homogenized bulk mixtures that have lost all textural petrologic information. Consequently, spectra collected on these powders represent an average spectrum of the bulk material in which the spectrally dominant component(s) may not be the volumetrically dominant component(s). With this in mind, the goals of this study are to: (1) assess the sub-mm spatial heterogeneity of the 3 μm absorption feature within individual C chondrite chips, and (2) to determine the extent to which bulk spectroscopic measurements might belie important information about the 3 μm feature below the spatial scale of individual components. Methods: We measured and mapped the sub-mm spatial scale reflectance spectra of individual CM2 chips from 1-16 μm with 4 cm-1 spectral resolution under dry air (dewpoint of -70°C) using a Bruker LUMOS microscope FTIR (μFTIR) spectrometer with spot sizes of 125 μm x 125 μm. These spectra were then compared to "bulk" IR spectra collected on the same meteorites using a NEXUS 870 FTIR with a spot size of 1-2 mm. Bulk modal mineralogy of separate powdered aliquots of the samples were modeled via Rietveld refinement of powder X-ray diffraction (XRD) patterns acquired with a Bruker D2 Phaser XRD. The meteorites selected for this study include Allan Hills (ALH) 84031, ALH 84048, Elephant Moraine (EET) 83226, EET 83389, Meteorite Hills (MET) 00630, MET 00639, and Queen Alexandra Range (QUE) 97077. Results & Discussion: The position of the 3 μm band minimum was calculated on the continuum-removed spectrum for each spot for every meteorite for comparison to the organizational scheme proposed by [4]. From these data we identify two apparent groups based on the variability of the position of the 3 μm feature: the spectrally homogeneous group (ALH 84031, ALH 84048, MET 00630) and the spectrally heterogeneous group (EET 83226, EET 83389, QUE 97077). The spectrally homogeneous group is characterized by 3 μm features with band minima positioned at shorter wavelengths that show much less variance in position. When considering statistical outliers, the range in 3 μm band positions for the spectrally homogeneous group extends from ~2.71-2.80 μm, which overlaps Groups 1, 2, and 3 from [4]. In other words, the 3 μm band positions found within individual meteorites spans the entire range of previously proposed taxonomic groups. The spectrally heterogeneous group is characterized by 3 μm band minima positioned at longer wavelengths that also span all three groups and show much more variability in position. Comparing the distribution of 3 μm band positions to the total abundance of phyllosilicates supports the relationship observed by [4] that spectra of the least altered C chodnrites (lower abundance of phyllosilicates) have 3 μm band features centered at longer wavelengths whereas spectra of the most altered samples exhibit 3 μm band positions at the shortest wavelengths. We also observe that the least altered meteorites (those with less phyllosilicates) exhibit the widest range of 3 μm band positions whereas those for the most altered show much less variance in band minimum position. Implications: The range of 3 μm features calculated for the most phyllosilicate-rich meteorites is relatively narrow and consistent in position with the bulk spectrum, which implies that the bulk reflectance spectrum is representative of the entire meteorite. This may be due to progressive aqueous alteration homogeneizing the mineralogy and chemistry of the meteorites at this spatial scale. However, CM chondrites are brecciated at all scales and may host multiple lithologies that have been aqueously altered to variable extents [5]. A larger survey of C chondrites would be needed to understand how genomict and polymict breccias influence spectra at sub-mm and bulk-scales. Alternatively, the least altered meteorite exhibit a wider range of 3 μm band minimums, which implies that the absorption feature calculated from the bulk reflectance spectrum may not necessarily be representative of the meteorite as a whole but is instead an average. By extension, asteroids exhibiting 3 μm absorption features in their reflectance spectra consistent with those measured here may be interpreted in a similar framework in which the spectrum of the least altered asteroids represents an average that belies the true diversity of mineralogy and chemistry of the body. [ABSTRACT FROM AUTHOR]

Abstract: Gale Crater contains a 5.2km-high central mound of layered material that is largely sedimentary in origin and has been considered as a potential landing site for both the MER (Mars Exploration Rover) and MSL (Mars Science Laboratory) missions. We have analyzed recent data from Mars Reconnaissance Orbiter to help unravel the complex geologic history evidenced by these layered deposits and other landforms in the crater. Results from imaging data from the High Resolution Imaging Science Experiment (HiRISE) and Context Camera (CTX) confirm geomorphic evidence for fluvial activity and may indicate an early lacustrine phase. Analysis of spectral data from the CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) instrument shows clay-bearing units interstratified with sulfate-bearing strata in the lower member of the layered mound, again indicative of aqueous activity. The formation age of the layered mound, derived from crater counts and superposition relationships, is ∼3.6–3.8Ga and straddles the Noachian–Hesperian time-stratigraphic boundary. Thus Gale provides a unique opportunity to investigate global environmental change on Mars during a period of transition from an environment that favored phyllosilicate deposition to a later one that was dominated by sulfate formation. [Copyright &y& Elsevier]

Abstract: Hydrated minerals on Mars are most commonly found in ancient terrains dating to the first billion years of the planet’s evolution. Here we discuss the identification of a hydrated light-toned rock unit present in one Chasma of the Noctis Labyrinthus region. Stratigraphy and topography show that this alteration layer is part of a thin unit that drapes pre-existing bedrock. CRISM spectral data show that the unit contains hydrated minerals indicative of aqueous alteration. Potential minerals include sulfates such as bassanite (CaSO4·1/2H2O) or possibly hydrated chloride salts. The proximity of a smooth volcanic plain and the similar crater model age (Late Amazonian, <100Myr) of this plain and the draping deposits suggest that the alteration layer may be formed by the interaction of water with ash layers deposited during this geologically recent volcanic activity. The alteration phases may have formed due to the presence of snow in contact with hot ash, or eventually solid–gas interactions due to the volcanic activity. The relatively young age of the volcanic plain implies that recent alteration processes have occurred on Mars in relation with volcanic activity, but such local processes do not require conditions different than the current climate. [Copyright &y& Elsevier]

Searching for water in the soil of Gale Crater is one of the primary tasks for the NASA Mars Science Laboratory rover named Curiosity. The primary task of the Dynamic Albedo of Neutrons (DAN) experiment on board the rover is to investigate and qualitatively characterize the presence of water along the rover’s traverse across Gale Crater. The water depth distribution may be found from measurements of neutrons generated by the Pulsing Neutron Generator (PNG) included in the DAN instrument, scattered by the regolith and returned back to the detectors. This paper provides a description of the data processing of such measurements and data products of DAN investigation. [ABSTRACT FROM AUTHOR]

Introduction: The spacecraft Hayabusa2 explored C-type asteroid Ryugu and brought back representative samples of Ryugu to the Earth in 2020 [1]. We performed reflectance spectroscopy of Ryugu samples to investigate (1) spectral diversity among Ryugu samples and (2) similarities and differences between Ryugu samples and carbonaceous chondrites. These results can also be applied to spectroscopic observations performed by the spacecraft [2,3]. Sample and Analysis: We measured Visible-infrared (Vis-IR, 0.4-18 μm in wavelength) reflectance spectra of 6 and 8 coarse grains (> 1mm in size) collected from the first and second touchdown sites, respectively, and some carbonaceous chondrites. Samples were put into an air-tight cell sealed with a CaF2 or ZnSe window together with reflectance standards. All the sample handling was performed in a pure-N2 -purged glove-box to avoid atmospheric alteration of the samples. Petrological and mineralogical characterization of the samples including synchrotron X-ray computed tomography and X-ray diffraction analysis was done by other analysis groups in the Hayabusa2 initial analysis "Stone" team [e.g., 4]. IR signature of Ryugu samples compared to hydrated chondrites: All the Ryugu coarse grains have an absorption band at ~2.71 μm attributed to Mg-rich phyllosilicates and a reflectance maximum (Reststrahlen band) at ~9.8 μm suggesting saponite-bearing phyllosilicate composition. These signatures of phyllosilicates of Ryugu are similar to those of CI chondrites, which is consistent with mineralogical observations of Ryugu samples [e.g., 4]. Ryugu sample spectra show absorption features due to aliphatic compounds (3.4 μm), carbonates (e.g., ~3.4, 3.95 μm), and some samples show an absorption feature at 5.8 μm probably due to carbonyl compounds [5]. Ryugu samples show a sharper 2.7 μm band than CIs, suggesting that they contain little molecular water compared to CIs. Sulfate features are not observed in Mid-IR reflectance spectra of Ryugu unlike CIs [e.g., 6]. Tagish Lake C2-ungrouped chondrite also shows an absorption band at ~2.7 μm and Reststrahlen band at ~9.8 μm. However, IR spectral features due to carbonates are more significant in the spectra of Tagish Lake than those of Ryugu as seen in absorption bands around ~3.4 μm and a reflectance maximum at 11.2 μm [7]. CM chondrites also consist mainly of hydrated minerals, however, their spectral shapes around ~3 μm and ~10 μm are different from those of Ryugu most likely due to the different phyllosilicate composition. Vis reflectance spectra of Ryugu samples: Ryugu coarse grains have ~2-4% of reflectance in the v-band (0.55 μm) at the phase angle of 30 °, which is roughly consistent with those of hydrated carbonaceous chondrites (CI, CM, Tagish Lake, and Tarda). The reflectance spectra of CO and CV chondrites, which are dominated by anhydrous minerals and more chondrule-rich, are brighter than those of Ryugu samples. The IR spectra suggest the compositional link between Ryugu and CI chondrites, however, Vis reflectance spectra of Ryugu are not similar to CI chondrites. Low reflectance Vis spectra without a UV drop (a sudden reflectance decrease towards UV wavelengths) of Ryugu samples are not similar to unheated Orgueil but similar to Orgueil samples heated at 300-400 °C for 50 hours (or longer) in reduced conditions [8]. The causes of differences between Vis spectra of Ryugu and unheated CIs may be explained by: (1) atmospheric alteration of CIs (e.g., oxidation and water adsorption of CIs [e.g., 9]), (2) different organic composition, and (3) gentle heating experienced by Ryugu. Vis reflectance spectra of Ryugu particles show some diversity of properties (reflectance, spectral slope, and overall shapes), while IR spectra are consistent among samples. This suggests that the spectral diversity of Ryugu samples are originated from physical properties or orientations of sample surfaces rather than the compositional differences among individual particles. [ABSTRACT FROM AUTHOR]

The Curiosity rover discovered fine-grained sedimentary rocks, which are inferred to represent an ancient lake and preserve evidence of an environment that would have been suited to support a martian biosphere founded on chemolithoautotrophy. This aqueous environment was characterized by neutral pH, low salinity, and variable redox states of both iron and sulfur species. Carbon, hydrogen, oxygen, sulfur, nitrogen, and phosphorus were measured directly as key biogenic elements; by inference, phosphorus is assumed to have been available. The environment probably had a minimum duration of hundreds to tens of thousands of years. These results highlight the biological viability of fluvial-lacustrine environments in the post-Noachian history of Mars. [ABSTRACT FROM AUTHOR]

We determined radiogenic and cosmogenic noble gases in a mudstone on the floor of Gale Crater. A K-Ar age of 4.21 ± 0.35 billion years represents a mixture of detrital and authigenic components and confirms the expected antiquity of rocks comprising the crater rim. Cosmic-ray-produced ³He, 21Ne, and 36Ar yield concordant surface exposure ages of 78 ± 30 million years. Surface exposure occurred mainly in the present geomorphic setting rather than during primary erosion and transport. Our observations are consistent with mudstone deposition shortly after the Gale impact or possibly in a later event of rapid erosion and deposition. The mudstone remained buried until recent exposure by wind-driven scarp retreat. Sedimentary rocks exposed by this mechanism may thus offer the best potential for organic biomarker preservation against destruction by cosmic radiation. [ABSTRACT FROM AUTHOR]

Phyllosilicates, a class of hydrous mineral first definitively identified on Mars by the OMEGA (Observatoire pour la Mineralogie, L’Eau, les Glaces et l’Activitié) instrument1,2, preserve a record of the interaction of water with rocks on Mars. Global mapping showed that phyllosilicates are widespread but are apparently restricted to ancient terrains and a relatively narrow range of mineralogy (Fe/Mg and Al smectite clays). This was interpreted to indicate that phyllosilicate formation occurred during the Noachian (the earliest geological era of Mars³), and that the conditions necessary for phyllosilicate formation (moderate to high pH and high water activity) were specific to surface environments during the earliest era of Mars’s history4. Here we report results from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM)5 of phyllosilicate-rich regions. We expand the diversity of phyllosilicate mineralogy with the identification of kaolinite, chlorite and illite or muscovite, and a new class of hydrated silicate (hydrated silica). We observe diverse Fe/Mg-OH phyllosilicates and find that smectites such as nontronite and saponite are the most common, but chlorites are also present in some locations. Stratigraphic relationships in the Nili Fossae region show olivine-rich materials overlying phyllosilicate-bearing units, indicating the cessation of aqueous alteration before emplacement of the olivine-bearing unit. Hundreds of detections of Fe/Mg phyllosilicate in rims, ejecta and central peaks of craters in the southern highland Noachian cratered terrain indicate excavation of altered crust from depth. We also find phyllosilicate in sedimentary deposits clearly laid by water. These results point to a rich diversity of Noachian environments conducive to habitability. [ABSTRACT FROM AUTHOR]

Investigates the replacement of metal by surface wave driven plasma column as the guiding medium in radio frequency antennas. Issues on antenna efficiency and noise; Prediction of high efficiency of surface wave driven plasma column; Advantages and disadvantages of plasma antennas.

The article focuses on the study which aims to examine the water content of Mar's Gale Crater which is located near the equator. Topics discussed include the National Aeronautics and Space Administration (NASA) Curiosity rover, the Dynamic Albedo of Neutrons experiment, and the epithermal neutron counter (CETN). It also discusses the data analysis for thermal and epithermal neutrons.