The Wet Chemistry Laboratory on the Phoenix Mars Lander performed aqueous chemical analyses of martian soil from the polygon-patterned northern plains of the Vastitas Borealis. The solutions ...contained approximately 10 mM of dissolved salts with 0.4 to 0.6% perchlorate (ClO₄) by mass leached from each sample. The remaining anions included small concentrations of chloride, bicarbonate, and possibly sulfate. Cations were dominated by Mg²⁺ and Na⁺, with small contributions from K⁺ and Ca²⁺. A moderately alkaline pH of 7.7 ± 0.5 was measured, consistent with a carbonate-buffered solution. Samples analyzed from the surface and the excavated boundary of the approximately 5-centimeter-deep ice table showed no significant difference in soluble chemistry.
Full text
Available for:
BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
The Sheepbed member of the Yellowknife Bay formation in Gale crater contains millimeter‐scale nodules that represent an array of morphologies unlike those previously observed in sedimentary deposits ...on Mars. Three types of nodules have been identified in the Sheepbed member in order of decreasing abundance: solid nodules, hollow nodules, and filled nodules, a variant of hollow nodules whose voids have been filled with sulfate minerals. This study uses Mast Camera (Mastcam) and Mars Hand Lens Imager (MAHLI) images from the Mars Science Laboratory Curiosity rover to determine the size, shape, and spatial distribution of the Sheepbed nodules. The Alpha Particle X‐Ray Spectrometer (APXS) and ChemCam instruments provide geochemical data to help interpret nodule origins. Based on their physical characteristics, spatial distribution, and composition, the nodules are interpreted as concretions formed during early diagenesis. Several hypotheses are considered for hollow nodule formation including origins as primary or secondary voids. The occurrence of concretions interpreted in the Sheepbed mudstone and in several other sedimentary sequences on Mars suggests that active groundwater systems play an important role in the diagenesis of Martian sedimentary rocks. When concretions are formed during early diagenetic cementation, as interpreted for the Sheepbed nodules, they have the potential to create a taphonomic window favorable for the preservation of Martian organics.
Key Points
Three types of nodules are observed in the Sheepbed mudstoneSheepbed nodules are interpreted as early diagenetic concretionsAuthigenic mineral precipitation was an important diagenetic process on Mars
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The ChemCam instrument package on the Mars Science Laboratory rover, Curiosity, is the first planetary science instrument to employ laser-induced breakdown spectroscopy (LIBS) to determine the ...compositions of geological samples on another planet. Pre-processing of the spectra involves subtracting the ambient light background, removing noise, removing the electron continuum, calibrating for the wavelength, correcting for the variable distance to the target, and applying a wavelength-dependent correction for the instrument response. Further processing of the data uses multivariate and univariate comparisons with a LIBS spectral library developed prior to launch as well as comparisons with several on-board standards post-landing. The level-2 data products include semi-quantitative abundances derived from partial least squares regression.
A LIBS spectral library was developed using 69 rock standards in the form of pressed powder disks, glasses, and ceramics to minimize heterogeneity on the scale of the observation (350–550μm dia.). The standards covered typical compositional ranges of igneous materials and also included sulfates, carbonates, and phyllosilicates. The provenance and elemental and mineralogical compositions of these standards are described. Spectral characteristics of this data set are presented, including the size distribution and integrated irradiances of the plasmas, and a proxy for plasma temperature as a function of distance from the instrument. Two laboratory-based clones of ChemCam reside in Los Alamos and Toulouse for the purpose of adding new spectra to the database as the need arises. Sensitivity to differences in wavelength correlation to spectral channels and spectral resolution has been investigated, indicating that spectral registration needs to be within half a pixel and resolution needs to match within 1.5 to 2.6pixels. Absolute errors are tabulated for derived compositions of each major element in each standard using PLS regression. Sources of errors are investigated and discussed, and methods for improving the analytical accuracy of compositions derived from ChemCam spectra are discussed.
► We describe a LIBS spectral training set of 69 geological standards. ► ChemCam Mars LIBS data processing is described. Detection limits are given. ► Laser coupling, plasma temperature, accuracy, and precision are detailed.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Chemical analyses of three Martian soil samples were performed using the Wet Chemistry Laboratories on the 2007 Phoenix Mars Scout Lander. One soil sample was obtained from the top ∼2 cm (Rosy Red) ...and two were obtained at ∼5 cm depth from the ice table interface (Sorceress 1 and Sorceress 2). When mixed with water in a ∼1:25 soil to solution ratio (by volume), a portion of the soil components solvated. Ion concentrations were measured using an array of ion selective electrodes and solution conductivity using a conductivity cell. The measured concentrations represent the minimum leachable ions in the soil and do not take into account species remaining in the soil. Described is the data processing and analysis for determining concentrations of seven ionic species directly measured in the soil/solution mixture. There were no significant differences in concentrations, pH, or conductivity, between the three samples. Using laboratory experiments, refinement of the surface calibrations, and modeling, we have determined a pH for the soil solution of 7.7(±0.3), under prevalent conditions, carbonate buffering, and PCO2 in the cell headspace. Perchlorate was the dominant anion in solution with a concentration for Rosy Red of 2.7(±1) mM. Equilibrium modeling indicates that measured Ca2+ at 0.56(±0.5) mM and Mg2+ at 2.9(±1.5) mM, are consistent with carbonate equilibrium for a saturated solution. The Na+ and K+ were 1.4(±0.6), and 0.36(±0.3) mM, respectively. Results indicate that the leached portion of soils at the Phoenix landing site are slightly alkaline and dominated by carbonate and perchlorate. However, it should be noted that there is a 5–15 mM discrepancy between measured ions and conductivity and another species may be present.
The vibrational frequency of the amide I transition of peptides is known to be sensitive to the strength of its hydrogen bonding interactions. In an effort to account for interactions with hydrogen ...bonding solvents in terms of electrostatics, we study the vibrational dynamics of the amide I coordinate of N-methylacetamide in prototypical polar solvents: D2O, CDCl3, and DMSO-d 6. These three solvents have varying hydrogen bonding strengths, and provide three distinct solvent environments for the amide group. The frequency−frequency correlation function, the orientational correlation function, and the vibrational relaxation rate of the amide I vibration in each solvent are retrieved by using three-pulse vibrational photon echoes, two-dimensional infrared spectroscopy, and pump−probe spectroscopy. Direct comparisons are made to molecular dynamics simulations. We find good quantitative agreement between the experimentally retrieved and simulated correlation functions over all time scales when the solute−solvent interactions are determined from the electrostatic potential between the solvent and the atomic sites of the amide group.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
•We describe various imaging experiments made by ChemCam’s Remote Microscopic Imager.•RMI gives the LIBS geological context and serves for long distance reconnaissance.•RMI provides clues regarding ...the origin of rocks and their diagenetic evolution.
The Mars Science Laboratory rover, “Curiosity” landed near the base of a 5km-high mound of layered material in Gale crater. Mounted on the rover mast, the ChemCam instrument is designed to remotely determine the composition of soils and rocks located a few meters from the rover, using a Laser-Induced Breakdown Spectrometer (LIBS) coupled to a Remote Micro-Imager (RMI). We provide an overview of the diverse imaging investigations that were carried out by ChemCam’s RMI during the first year of operation on Mars. 1182 individual panchromatic RMI images were acquired from Sol 10 to Sol 360 to document the ChemCam LIBS measurements and to characterize soils, rocks and rover hardware. We show several types of derived imaging products, including mosaics of images taken before and after laser shots, difference images to enhance the most subtle laser pits, merges with color Mastcam-100 images, micro-topography using the Z-stack technique, and time lapse movies. The very high spatial resolution of RMI is able to resolve rock textures at sub-mm scales, which provides clues regarding the origin (igneous versus sedimentary) of rocks, and to reveal information about their diagenetic and weathering evolution. In addition to its scientific value over the range accessible by LIBS (1–7m), we also show that RMI can also serve as a powerful long distance reconnaissance tool to characterize the landscape at distances up to several kilometers from the rover.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Data gathered with the Dynamic Albedo of Neutron (DAN) instrument onboard rover Curiosity were analyzed for variations in subsurface neutron flux and tested for possible correlation with local ...geological context. A special DAN observation campaign was executed, in which 18 adjacent DAN active measurements were acquired every 0.75–1.0 m to search for the variations of subsurface hydrogen content along a 15 m traverse across geologic contacts between the Sheepbed and Gillespie Lake members of the Yellowknife Bay formation. It was found that several subunits in Sheepbed and Gillespie Lake could be characterized with different depth distributions of water‐equivalent hydrogen (WEH) and different chlorine‐equivalent abundance responsible for the distribution of neutron absorption elements. The variations of the average WEH at the top 60 cm of the subsurface are estimated at up to 2–3%. Chlorine‐equivalent neutron absorption abundances ranged within 0.8–1.5%. The largest difference in WEH and chlorine‐equivalent neutron absorption distribution is found between Sheepbed and Gillespie Lake.
Key Points
DAN special campaign in Yellowknife Bay
DAN local measurements of water and chlorine abundance
Correlation of DAN measurements and geological context
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
•Passive ChemCam observations were used to retrieve relative reflectance spectra of Mars.•First high spectral/spatial resolution 400–840nm in situ observations of Mars.•Spectra consistent with ...iron-bearing oxides, pyroxenes, and calcium sulfates.
The spectrometers on the Mars Science Laboratory (MSL) ChemCam instrument were used in passive mode to record visible/near-infrared (400–840nm) radiance from the martian surface. Using the onboard ChemCam calibration targets’ housing as a reflectance standard, we developed methods to collect, calibrate, and reduce radiance observations to relative reflectance. Such measurements accurately reproduce the known reflectance spectra of other calibration targets on the rover, and represent the highest spatial resolution (0.65mrad) and spectral sampling (<1nm) visible/near-infrared reflectance spectra from a landed platform on Mars. Relative reflectance spectra of surface rocks and soils match those from orbital observations and multispectral data from the MSL Mastcam camera. Preliminary analyses of the band depths, spectral slopes, and reflectance ratios of the more than 2000 spectra taken during the first year of MSL operations demonstrate at least six spectral classes of materials distinguished by variations in ferrous and ferric components. Initial comparisons of ChemCam spectra to laboratory spectra of minerals and Mars analog materials demonstrate similarities with palagonitic soils and indications of orthopyroxene in some dark rocks. Magnesium-rich “raised ridges” tend to exhibit distinct near-infrared slopes. The ferric absorption downturn typically found for martian materials at <600nm is greatly subdued in brushed rocks and drill tailings, consistent with their more ferrous nature. Calcium-sulfate veins exhibit the highest relative reflectances observed, but are still relatively red owing to the effects of residual dust. Such dust is overall less prominent on rocks sampled within the “blast zone” immediately surrounding the landing site. These samples were likely affected by the landing thrusters, which partially removed the ubiquitous dust coatings. Increased dust coatings on the calibration targets during the first year of the mission were documented by the ChemCam passive measurements as well. Ongoing efforts to model and correct for this dust component should improve calibration of the relative reflectance spectra. This will be useful as additional measurements are acquired during the rover’s future examinations of hematite-, sulfate-, and phyllosilicate-bearing materials near the base of Mt. Sharp that are spectrally active in the 400–840nm region.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The Dynamic Albedo of Neutrons (DAN) instrument on board Mars Science Laboratory has been operating successfully since the landing and has been making measurements regularly along Curiosity's ...traverse at the surface. DAN measures thermal (E < 0.4 eV) and epithermal neutrons (0.4 eV < E < ~1 keV) while operating in two different modes: active and passive. The active mode uses a pulsed neutron generator (PNG) to study the geological characteristics of the subsurface. In the passive mode, DAN measures the background neutron environment. This paper presents results of measurements in the passive mode from landing through to sol 100 and provides an interpretation of the data based on extensive Monte Carlo simulations. The main observations are summarized as follows: (1) the thermal neutron counts vary strongly along the rover traverse while the epithermal counts do not show much variation; (2) the neutrons from the Multi‐Mission Radioisotope Thermoelectric Generator (MMRTG) are a larger contributor to the DAN passive data than the Galactic Cosmic Ray (GCR)‐induced neutrons; (3) for the MMRTG neutrons, both the thermal and the epithermal counts increase as a function of the subsurface water content; (4) on the other hand, for the GCR‐induced neutrons, the thermal counts increase but the epithermal counts decrease as a function of the subsurface water content; and (5) relative contributions by the MMRTG and GCR to the DAN thermal neutron counts at the Rocknest site, where the rover was stationed from sol 59 to sol 100, are estimated to be ~60% and ~40%, respectively.
Key Points
The DAN passive mode measures the MMRTG neutrons and GCR‐induced neutrons
The thermal neutron counts show strong variability along the rover traverse
The majority of the DAN passive counts are from the MMRTG neutrons
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
PDF
