Estimated Detection Limits of Carboxylates in Palagonite by X-ray Diffraction and Reflectance Spectroscopy

Low molecular weight carboxylates (carbonates, oxalates, formates, and acetates) are either known or are expected to be present on the surface of Mars. Previous work has suggested these phases to be present in Gale Crater materials at nearly the expected detection limit (LOD) for crystalline materials with the Mars Science Laboratory (MSL)Curiosity rover CheMin X-ray diffraction (XRD) instrument. Detection limits of these materials by CheMin-like XRD and reflectance spectroscopy are poorly constrained, thus leading to uncertainties in detectability with these types of instruments. I have filled this knowledge gap by making intimate mixtures of a variety of carboxylates with the JSC Mars-1a regolith analogue material and measured their XRD patterns with a CheMin-like breadboard and reflectance spectra with instruments analogous to the SuperCam instrument on the Mars Perseverance rover. I used simple linear regression to create calibration curves to estimate LODs and compared and contrasted ten different LOD calculations previously used for XRD. I found that the carboxylates measured have LODs near 1.0 wt.% by XRD. Oxalate minerals are likely undetectable by reflectance spectroscopy in bulk materials at expected concentrations, while acetate and formate minerals have relatively low LODs at near-infrared wavelengths due to their sharp and strong absorption bands. Carbonate minerals may show decreasing LODs with increasing grain size in reflectance spectra and have relatively high LODs at near-infrared wavelengths for fine grained powders and relatively low LODs when using the 3950 nm absorption band at all grain sizes. Application of these data to CheMin observations show that my data could accurately detect low concentrations of siderite at nearly the same values determined from previous CheMin data processing within error and within an average of 0.5-1.0 wt.% where siderite was detected. After applying the calibration curves from the other carboxylates, I did not find strong evidence for their detection in any of the CheMin data. Some samples, primarily the Gale crater Rocknest aeolian material may contain some concentration of whewellite which may be consistent with the analysis of the Sample Analysis at Mars (SAM) data, but detection may be complicated by overlapping plagioclase Bragg peaks. I applied the measured reflectance spectra from 350 to 4000 nm to some data collected by the SuperCam instrument at Jezero crater that were implied to contain organic compounds through analysis of Perseverance Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) data. I did not find evidence for carboxylates in the reflectance spectra except for Mg-rich anhydrous carbonates, and I determined the concentration to be between roughly 5.0 and 20.0 wt.%, which is broadly consistent with the previous analyses of these samples by radiative transfer modelling.Master of Science in Environmental and Social Chang

Detection of Rotational Spectral Variation on the M-type asteroid (16) Psyche

The asteroid (16) Psyche is of scientific interest because it contains ~ 1% of the total mass of the asteroid belt and is thought to be the remnant metallic core of a protoplanet. Radar observations have indicated the significant presence of metal on the surface with a small percentage of silicates. Prior ground-based observations showed rotational variations in the near-infrared (NIR) spectra and radar albedo of this asteroid. However, no comprehensive study that combines multi-wavelength data has been conducted so far. Here we present rotationally resolved NIR spectra (0.7-2.5 microns) of (16) Psyche obtained with the NASA Infrared Telescope Facility. These data have been combined with shape models of the asteroid for each rotation phase. Spectral band parameters extracted from the NIR spectra show that the pyroxene band center varies from ~ 0.92 to 0.94 microns. Band center values were used to calculate the pyroxene chemistry of the asteroid, whose average value was found to be Fs30En65Wo5. Variations in the band depth were also observed, with values ranging from 1.0 to 1.5%. Using a new laboratory spectral calibration we estimated an average orthopyroxene content of 6+/-1%. The mass-deficit region of Psyche, which exhibits the highest radar albedo, also shows the highest value for spectral slope and the minimum band depth. The spectral characteristics of Psyche suggest that its parent body did not have the typical structure expected for a differentiated body or that the sequence of events that led to its current state was more complex than previously thought.Comment: 21 pages, 8 figures, 2 tables, published in The Astronomical Journa

Cryogenic silicification of microorganisms in hydrothermal fluids

Silica-rich hydrothermal fluids that experience freezing temperatures precipitate cryogenic opal-A (COA) within ice-bound brine channels. We investigated cryogenic silicification as a novel preservation pathway for chemo- and photo-lithotrophic Bacteria and Archaea. We find that the co-partitioning of microbial cells and silica into brine channels causes microorganisms to become fossilised in COA. Rod- and coccoidal-form Bacteria and Archaea produce numerous cell casts on COA particle surfaces, while Chloroflexus filaments are preserved inside particle interiors. COA particles precipitated from natural Icelandic hot spring fluids possess similar biomorphic casts, including those containing intact microbial cells. Biomolecules and inorganic metabolic products are also captured by COA precipitation, and are detectable with a combination of visible - shortwave infrared reflectance, FTIR, and Raman spectroscopy. We identify cryogenic silicification as a newly described mechanism by which microbial biosignatures can be preserved within silica-rich hydrothermal environments. This work has implications for the interpretation of biosignatures in relic hydrothermal settings, and for life-detection on Mars and Enceladus, where opaline silica indicative of hydrothermal activity has been detected, and freezing surface conditions predominate

Natural Analogue Constraints on Europa's Non-ice surface Material

Non-icy material on the surface of Jupiter’s moon Europa is hypothesised to have originated from its subsurface ocean, and thus provide a record of ocean composition and habitability. The nature of this material is debated, but observations suggest that it comprises hydrated sulfate and chloride salts. Analogue spectroscopic studies have previously focused on single phase salts under controlled laboratory conditions. We investigated natural salts from perennially cold (<0 °C) hypersaline springs, and characterised their reflectance properties at 100 K, 253 K and 293 K. Despite similar major ion chemistry, these springs form mineralogically diverse deposits, which when measured at 100 K closely match reflectance spectra from Europa. In the most sulfate-rich samples, we find spectral features predicted from laboratory salts are obscured. Our data are consistent with sulfate-dominated europan non-icy material, and further, show that the emplacement of endogenic sulfates on Europa’s surface would not preclude a chloride-dominated ocean

Mobility of arsenic and vanadium in waterlogged calcareous soils due to addition of zeolite and manganese oxide amendments

Addition of manganese(IV) oxides (MnO2) and zeolite can affect the mobility of As and V in soils due to geochemical changes that have not been studied well in calcareous, flooded soils. This study evaluated the mobility of As and V in flooded soils surface-amended with MnO2 or zeolite. A simulated summer flooding study was conducted for 8 weeks using intact soil columns from four calcareous soils. Redox potential was measured in soils, whereas pH, major cations, and As and V concentrations were measured biweekly in pore water and floodwater. Aqueous As and V species were modeled at 0, 4, and 8 weeks after flooding (WAF) using Visual MINTEQ modeling software with input parameters of redox potential, temperature, pH, total alkalinity, and concentrations of major cations and anions. Aqueous As concentrations were below the critical thresholds (<100 μg L−1), whereas aqueous V concentrations exceeded the threshold for sensitive aquatic species (2–80 μg L−1). MnO2-amended soils were reduced to sub-oxic levels, whereas zeolite-amended and unamended soils were reduced to anoxic levels by 8 WAF. MnO2 decreased As and V mobilities, whereas zeolite had no effect on As but increased V mobility, compared to unamended soils. Arsenic mobility increased under anoxic conditions, and V mobility increased under oxic and alkaline pH conditions. Conversion of As(V) to As(III) and V(V) to V(IV) was regulated by MnO2 in flooded soils. MnO2 can be used as an amendment in immobilizing As and V, whereas the use of zeolite in flooded calcareous soils should be done cautiously."This research was financially supported by Environment and Climate Change Canada through Lake Winnipeg Basin Program, University of Winnipeg Major Grant and Canadian Queen Elizabeth II Diamond Jubilee Scholarships: Advanced Scholars program."https://acsess.onlinelibrary.wiley.com/doi/10.1002/jeq2.2045

Detection of rotational spectral variation on the M-type asteroid (16) Psyche

The asteroid (16) Psyche is of scientific interest because it contains ∼1% of the total mass of the asteroid belt and is thought to be the remnant metallic core of a protoplanet. Radar observations have indicated the significant presence of metal on the surface with a small percentage of silicates. Prior ground-based observations showed rotational variations in the near-infrared (NIR) spectra and radar albedo of this asteroid. However, no comprehensive study that combines multi-wavelength data has been conducted so far. Here we present rotationally resolved NIR spectra (0.7–2.5 μm) of (16) Psyche obtained with the NASA Infrared Telescope Facility. These data have been combined with shape models of the asteroid for each rotation phase. Spectral band parameters extracted from the NIR spectra show that the pyroxene band center varies from ∼0.92 to 0.94 μm. Band center values were used to calculate the pyroxene chemistry of the asteroid, whose average value was found to be Fs30En65Wo5. Variations in the band depth (BD) were also observed, with values ranging from 1.0% to 1.5%. Using a new laboratory spectral calibration method, we estimated an average orthopyroxene content of 6% ± 1%. The mass-deficit region of Psyche, which exhibits the highest radar albedo, also shows the highest value for the spectral slope and the minimum BD. The spectral characteristics of Psyche suggest that its parent body did not have the typical structure expected for a differentiated body or that the sequence of events that led to its current state was more complex than previously thought.This research work was supported by NASA Planetary Mission Data Analysis Program Grant NNX13AP27G, NASA NEOO Program Grant NNX12AG12G, and NASA Planetary Geology and Geophysics Program Grant NNX11AN84G… The Arecibo Planetary Radar Program is supported by the National Aeronautics and Space Administration under Grant Nos. NNX12AF24G and NNX13AQ46G, issued through the Near Earth Object Observations program. E.A.C. thanks the Canada Foundation for Innovation, the Manitoba Research Innovations Fund, the Canadian Space Agency, the Natural Sciences and Engineering Research Council of Canada, and the University of Winnipeg for supporting the establishment and ongoing operation of the University of Winnipeg’s Planetary Spectrophotometer Facility.http://iopscience.iop.org/article/10.3847/1538-3881/153/1/29/met

Biosignature detection by Mars rover equivalent instruments in samples from the CanMars Mars Sample Return Analogue Deployment

The University of Winnipeg's HOSERLab was established with funding from the Canada Foundation for Innovation, the Manitoba Research Innovations Fund and the Canadian Space Agency, whose support is gratefully acknowledged. This study was supported with grants from the Canadian Space Agency through their FAST program, NSERC, and UWinnipeg.This work details the laboratory analysis of a suite of 10 samples collected from an inverted fluvial channel near Hanksville, Utah, USA as a part of the CanMars Mars Sample Return Analogue Deployment (MSRAD). The samples were acquired along the rover traverse for detailed off-site analysis to evaluate the TOC and astrobiological significance of the samples selected based on site observations, and to address one of the science goals of the CanMars mission: to evaluate the ability of different analytical techniques being employed by the Mars2020 mission to detect and characterize any present biosignatures. Analytical techniques analogous to those on the ExoMars, MSL and the MER rovers were also applied to the samples. The total organic carbon content of the samples was <0.02% for all but 4 samples, and organic biosignatures were detected in multiple samples by UV–Vis–NIR reflectance spectroscopy and Raman spectroscopy (532 nm, time-resolved, and UV), which was the most effective of the techniques. The total carbon content of the samples is < 0.3 wt% for all but one calcite rich sample, and organic C was not detectable by FTIR. Carotene and chlorophyll were detected in two samples which also contained gypsum and mineral phases of astrobiological importance for paleoenvironment/habitability and biomarker preservation (clays, gypsum, calcite) were detected and characterized by multiple techniques, of which passive reflectance was most effective. The sample selected in the field (S2) as having the highest potential for TOC did not have the highest TOC values, however, when considering the sample mineralogy in conjunction with the detection of organic carbon, it is the most astrobiologically relevant. These results highlight importance of applying multiple techniques for sample characterization and provide insights into their strengths and limitations.PostprintPeer reviewe