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NASA NTRS2014

The Deuterium to Hydrogen Ratio in the Water that Formed the Yellowknife Bay Mudstones in Gale Crater

A suite of isotope ratios of light elements in the present martian atmosphere (13C/12C, 15N/14N, 18O/16O, 38Ar/36Ar, and D/H) are all substantially enriched in the heavy element suggesting atmospheric loss to space over the past billions of years with preferential loss of the lighter isotope from each pair. In situ measurements from MSL's Sample Analysis at Mars (SAM) instrument [e.g. 1,2,3] have considerably refined previous measurements from the Viking mass spectrometers [e.g. 4], from remote spectroscopic observations [e.g. 5,6], and from martian meteorite studies [e.g. 7,8]. The persistence of habitable environments such as the ancient Yellowknife Bay lake recently revealed by measurements from the Curiosity rover [9] depends on the surface temperatures and the duration of an atmosphere thicker than that at present. Current and planned measurements from orbit with the Mars Express and MAVEN missions respectively intend to study the processes of atmospheric escape including solar wind interaction, sputtering, thermal escape, and dissociative recombination, and determine or refine the current rate of atmospheric loss caused by these and other mechanisms. The goal of these programs is to understand the physical processes sufficiently well so that robust extrapolations over the past billions of years can be made D/H is measured by both the Tunable Laser Spectrometer (TLS) and the Quadrupole Mass Spectrometer (QMS) of the SAM suite. to predict the atmospheric and surface conditions on early Mars. However, the study of the history of martian atmospheric evolution will be greatly facilitated if we are able to also directly measure the isotopic composition of volatiles captured in rocks that are representative of the ancient atmosphere. To date, D/H is one of the most promising candidates for this study since water is the most abundant volatile thermally released from the Yellowknife Bay phylosilicates discovered by the SAM and CheMin experiments of MSL and its

Yellowknife Bay↗

NASA NTRS2013

Isotopic and Geochemical Investigation of Two Distinct Mars Analog Environments Using Evolved Gas Techniques in Svalbard, Norway

The 2010 Arctic Mars Analog Svalbard Expedition (AMASE) investigated two distinct geologic settings on Svalbard, using methodologies and techniques to be deployed on Mars Science Laboratory (MSL). AMASErelated research comprises both analyses conducted during the expedition and further analyses of collected samples using laboratory facilities at a variety of institutions. The Sample Analysis at Mars (SAM) instrument suite on MSL includes pyrolysis ovens, a gas-processing manifold, a quadrupole mass spectrometer (QMS), several gas chromatography columns, and a Tunable Laser Spectrometer (TLS). An integral part of SAM development is the deployment of SAM-like instrumentation in the field. During AMASE 2010, two parts of SAM participated as stand-alone instruments. A Hiden Evolved Gas Analysis- Mass Spectrometer (EGA-QMS) system represented the EGA-QMS component of SAM, and a Picarro Cavity Ring Down Spectrometer (EGA-CRDS), represented the EGA-TLS component of SAM. A field analog of CheMin, the XRD/XRF on MSL, was also deployed as part of this field campaign. Carbon isotopic measurements of CO2 evolved during thermal decomposition of carbonates were used together with EGA-QMS geochemical data, mineral composition information and contextual observations made during sample collection to distinguish carbonates formation associated with chemosynthetic activity at a fossil methane seep from abiotic processes forming carbonates associated with subglacial basaltic eruptions. Carbon and oxygen isotopes of the basalt-hosted carbonates suggest cryogenic carbonate formation, though more research is necessary to clarify the history of these rocks.

Svalbard↗

NASA NTRS2014

Chemical Evidence for Smectites and Zeolites on Mars: Criteria and Limitations

Aqueous alteration on Mars can produce a range of tell-tale secondary minerals [1]. Surface missions typically obtain detailed and highly localized element compositional information, but not always mineralogical information, whereas orbital missions deduce mineralogy from relatively high spatial resolution IR spectral mapping (decameters scale, for CRISM), but obtain element data only over much larger areas of martian terrain (~200 km). Surface missions have also discovered several occurrences of major geochemical alteration of igneous precursors, for many of which elemental compositional is the only diagnostic information available. Many types of clays and zeolites have quasi-unique element profiles which may be used to implicate their presence. In some cases, one or more candidate minerals are sufficiently close in their component elements and their stoichiometry that ambiguity must remain, unless other constraints can be brought to bear. Geochemical characteristics of alteration products most likely on Mars can be compared to results from MER and MSL rover missions (e.g. Independence [4] and Esperance samples). These considerations are needed for MER Opportunity rover now that Mini-TES is no longer operational. It also has importance for exploration by the MSL Curiosity rover because inferences and deductions available from ChemCam (CCAM) remote LIBS and/or in situ x-ray fluorescence (APXS) can be used as indicators for triage to select materials to sample for limited-resource instruments, SAM and Chemin.

Clark, B. C.↗

NASA NTRS2012

The Influence of Mineralogy on Recovering Organic Acids from Mars Analogue Materials Using the One-Pot Derivatization Experiment on the Sample Analysis at Mars(SAM) Instrument Suite

The search for complex organic molecules on Mars, including important biomolecules such as amino acids and carboxylic acids, will require a chemical extraction and a derivatization step to transform these organic compounds into species that are sufficiently volatile to be detected by gas chromatography mass spectrometry (GCMS). We have developed a ''one-pot'' extraction and chemical derivatization protocol using N-methyl-N-(tert-butyldimethylsilyl) trifluoroacetamide (MTBSTFA) and dimethylformamide (DMF) for the Sample Analysis at Mars (SAM) experiment instrument suite on NASA's the Mars Science Laboratory (MSL) mission. The temperature and duration of the derivatization reaction, pre-concentration of chemical derivatives, and gas chromatographic separation parameters have been optimized under SAM instrument design constraints. MTBSTFA/DMF extraction and derivatization at 300 1C for several minutes of a variety of terrestrial Mars analog materials facilitated the detection of amino acids and carboxylic acids in a surface soil sample collected from the Atacama Desert and a carbonate-rich stromatolite sample from Svalbard. However, the rapid reaction of MTBSTFA with water in several analog materials that contained high abundances of hydrated minerals, and the possible deactivation of derivatized compounds by iron oxides, as detected by XRD/XRF using the CheMin field unit Terra, proved to be highly problematic for the direct extraction of organics using MTBSTFA. The combination of pyrolysis and two different wet-chemical derivatization methods employed by SAM should enable a wide range of organic compounds to be detected by GCMS if present on Mars.

MSL↗

NASA NTRS2014

Paleoenvironmental Implications of Clay Minerals at Yellowknife Bay, Gale Crater, Mars

The Mars Science Laboratory (MSL) Rover, Curiosity spent approx 150 sols at Yellowknife Bay (YKB) studying a section of fluvio-lacustrine sedimentary rocks (with potential indications of volcanic influence), informally known as the Yellowknife Bay formation. YKB lies in a distal region of the Peace Vallis alluvial fan, which extends from the northern rim of Gale Crater toward the dune field at the base of Mt Sharp. Sedimentological and stratigraphic observations are consistent with the Yellowknife Bay formation being part of a distal fan deposit, which could be as young as middle Hesperian to even early Amazonian in age (approx. 3.5 to 2.5 Ga). The Yellowknife Bay formation hosts a unit of mudstone called the Sheepbed member. Curiosity obtained powdered rock samples from two drill holes in the Sheepbed Member, named John Klein and Cumberland, and delivered them to instruments in Curiosity. Data from CheMin, a combined X-ray diffraction (XRD)/X-ray fluorescence instrument (XRF), has allowed detailed mineralogical analysis of mudstone powders revealing a clay mineral component of approx. 20 wt.% in each sample. The clay minerals are important indicators of paleoenvironmental conditions and sensitive recorders of post-depositional alteration processes. The XRD pattern of John Klein reveals a 02l band consistent with a trioctahedral phyllosilicate. A broad peak at approx. 10A with a slight inflexion at approx. 12A indicates the presence of 2:1 type clay minerals in the John Klein sample. The trioctahedral nature of the clay minerals, breadth of the basal reflection, and presence of a minor component with larger basal spacing suggests that John Klein contains a trioctahedral smectite (probably saponite), whose interlayer is largely collapsed because of the low-humidity conditions. The XRD patterns show no evidence of corrensite (mixed-layer chlorite/smectite) or chlorite, which are typical diagenetic products of trioctahedral smectites when subjected to burial and heating >60 C in the presence of water. Given estimated geothermal gradients on Mars temperatures <60 C might still be consistent with (but do not require) moderate burial. However, our ability to identify interstratified minerals is greatly limited by the lack of access to traditional treatments methods used in the lab (e.g., ethylene glycol solvation). Our preferred explanation for the origin of trioctahedral smectites in Sheepbed mudstone is in situ production via reaction of olivine, water and Si-bearing amorphous material, an important mudstone component detected by XRD. Elevated levels of magnetite in the Sheepbed and the trioctahedral monomineralic nature of the clay minerals support this model. These observations, combined with previous studies of olivine stability, support the persistence of circum-neutral hydrous conditions for thousands of years at YKB.

MSL↗

NASA NTRS2014

Origin of Chlorobenzene Detected by the Curiosity Rover in Yellowknife Bay: Evidence for Martian Organics in the Sheepbed Mudstone?

The Sample Analysis at Mars (SAM) instrument on the Curiosity rover is designed to determine the inventory of organic and inorganic volatiles thermally evolved from solid samples using a combination of evolved gas analysis (EGA), gas chromatography mass spectrometry (GCMS), and tunable laser spectroscopy. The first solid samples analyzed by SAM, a scoop of windblown dust and sand at Rocknest (RN), revealed chlorinated hydrocarbons derived primarily from reactions between a martian oxychlorine phase (e.g. perchlorate) and terrestrial carbon from N-methyl-N-(tert-butyldimethylsilyl)-trifluoroacetamide (MTBSTFA) vapor present in the SAM instrument background. Chlorobenzene (CBZ) was also identified by SAM GCMS at RN at trace levels (approx.0.007 nmol) and was attributed to the reaction of chlorine with the Tenax polymers used in the hydrocarbon traps. After the RN analyses, Curiosity traveled to Yellowknife Bay and drilled two separate holes designated John Klein (JK) and Cumberland (CB). Analyses of JK and CB by both SAM and the CheMin x-ray diffraction instrument revealed a mudstone consisting of approx.20 wt% smectite clays, which on Earth are known to aid the concentration and preservation of organic matter. In addition, higher abundances and a more diverse suite of chlorinated hydrocarbons in CB compared to RN suggests that martian or meteoritic organic sources may be preserved in the mudstone. Here we discuss the SAM EGA and GCMS measurements of volatiles released from the Sheepbed mudstone. We focus primarily on the elevated CBZ detections at CB and laboratory analog experiments conducted to help determine if CBZ is derived from primarily terrestrial, martian, or a combination of sources.

origin of↗

NASA NTRS2015

Mineralogy and Genesis of the Windjana Sandstone, Kimberley Area, Gale Crater, Mars

MSL Curiosity investigated the Windjana sandstone outcrop, in the Kimberley area of Gale Crater, and obtained mineralogical analyses with the CheMin XRD instrument. Windjana is remarkable in containing an abundance of potassium feldspar (and thus K in its bulk chemistry) combined with a low abundance of plagioclase (and low Na/K in its chemistry). The source of this enrichment in K is not clear, but has significant implications for the geology of Gale Crater and of Mars. The high K could be intrinsic to the sediment and imply that the sediment source area (Gale Crater rim) includes K-rich basalts and possibly more evolved rocks derived from alkaline magmas. Alternatively, the high K could be diagenetic and imply that the Gale Crater sediments were altered by K-rich aqueous fluids after deposition.

Treiman, A. H.↗

NASA NTRS2015

Effect of Sulfur Concentration and PH Conditions on Akaganeite Formation: Understanding Akaganeite Formation Conditions in Yellowknife Bay, Gale Crater, Mars

The Chemistry and Mineralogy Instrument (CHEMIN) on board the Mars Science Laboratory (MSL) Curiosity Rover identified minor amounts of akaganeite (beta-FeOOH) at Yellowknife Bay, Mars. There is also evidence for akaganeite at other localities on Mars from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). Akaganeite is an iron(III) hydroxide with a hollandite- like structure and Cl in its tunnels. Terrestrial akaganeite usually forms in Cl-rich environments under acidic, oxidizing conditions. Previous studies of akaganeite have revealed that akaganeite formation is affected by the presence of sulfate (hereafter denoted as S. The prediction of circumneutral pH coupled with the detection of S at Yellowknife Bay dictate that work is needed to determine how S and pH together affect akaganeite formation. The goal of this work is to study how changes in both S concentration and pH influence akaganeite precipitation. Akaganeite formation was investigated at S/Cl molar ratios of 0, 0.017, 0.083, 0.17 and 0.33 at pH 1.5, 2, and 4. Results are anticipated to provide combined S concentration and pH constraints on akaganeite formation in Yellowknife Bay and elsewhere on Mars. Knowledge of solution pH and S concentrations can be utilized in understanding microbial habitability potential on the Martian surface.

Fox, A.↗

NASA NTRS2015

Oxychlorine Species on Mars: The Gale Crater Story

Comparing data from the Alpha- Particle X-Ray Spectrometer (APXS) and the Sample Analysis at Mars (SAM) instruments on MSL reveals a strong linear correlation between chlorine and oxygen, further demonstrating the presence of oxychlorine species in Gale Crater and, very likely, globally on Mars. Perchlorate was first discovered on Mars by the Microscopy, Electrochemistry, and Conductivity Analyzer (MECA) instrument on the Phoenix lander in 2008. Current hypotheses suggest that the formation of oxychlorine species such as perchlorate or chlorate is a global process and that these species should be globally distributed on Mars [e.g. 2-4]. To date, the SAM and Chemistry and Mineralogy (CheMin) instruments on MSL have analyzed one scooped sample of aeolian material (Rocknest [RN]), and four drilled samples (John Klein [JK], Cumberland [CB], Windjana [WJ], and Confidence Hills [CH]). The APXS instrument has also investigated the same or very similar samples. Although not definitively identified, oxychlorine species have been proposed to explain releases of O2, HCl, and chlorinated hydrocarbon species detected by evolved gas analysis (EGA) with the SAM instrument. We report a strong linear correlation between wt. % Cl detected by APXS and moles O2 detected by SAM during pyrolysis, indicating the presence of oxychlorine species in Gale Crater.

Archer, P. D., Jr.↗

NASA NTRS2015

Martian Chlorobenzene Identified by Curiosity in Yellowknife Bay: Evidence for the Preservation of Organics in a Mudstone on Mars

The Sample Analysis at Mars (SAM) instrument on the Curiosity rover is designed to determine the inventory of organic and inorganic volatiles thermally evolved from solid samples using a combination of evolved gas analysis (EGA), gas chromatography mass spectrometry (GCMS), and tunable laser spectroscopy. The first sample analyzed by SAM at the Rocknest (RN) aeolian deposit revealed chlorohydrocarbons derived primarily from reactions between a martian oxychlorine phase (e.g. perchlorate) and terrestrial carbon from N-methyl-N-(tert-butyldimethylsilyl) trifluoroacetamide (MTBSTFA) vapor present in the SAM instrument background. No conclusive evidence for martian chlorohydrocarbons in the RN sand was found. After RN, Curiosity traveled to Yellowknife Bay and drilled two holes separated by 2.75 m designated John Klein (JK) and Cumberland (CB). Analyses of JK and CB by both SAM and the CheMin x-ray diffraction instrument revealed a mudstone (called Sheepbed) consisting of approx.20 wt% smectite clays, which on Earth are known to aid the concentration and preservation of organic matter. Last year at LPSC we reported elevated abundances of chlorobenzene (CBZ) and a more diverse suite of chlorinated hydrocarbons including dichloroalkanes in CB compared to RN, suggesting that martian or meteoritic organic compounds may be preserved in the mudstone. Here we present SAM data from additional analyses of the CB sample and of Confidence Hills (CH), another drill sample collected at the base of Mt. Sharp. This new SAM data along with supporting laboratory analog experiments indicate that most of the chlorobenzene detected in CB is derived from martian organic matter preserved in the mudstone.

Glavin, D.↗

NASA NTRS2015

Constraining the Texture and Composition of Pore-Filling Cements at Gale Crater, Mars

The Mars Science Laboratory (MSL) rover Curiosity has encountered a wide variety of sedimentary rocks deposited in fluvio-lacuestrine sequences at the base of Gale Crater. The presence of sedimentary rocks requires that initial sediments underwent diagenesis and were lithified. Lithification involves sediment compaction, cementation, and re-crystallization (or authigenic) processes. Analysis of the texture and composition of the cement can reveal the environmental conditions when the cements were deposited, enabling better understanding of early environments present within Gale Crater. The first step in lithification is sediment compaction. The Gale crater sediments do not show evidence for extensive compaction prior to cementation; the Sheepbed mudstone in Yellowknife Bay (YKB) has preserved void spaces ("hollow nodules"), indicating that sediments were cemented around the hollow prior to compaction, and conglomerates show imbrication, indicating minimal grain reorganization prior to lithification. Furthermore, assuming the maximum burial depth of these sediments is equivalent to the depth of Gale Crater, the sediments were never under more than 1 kb of pressure, and assuming a 15 C/km thermal gradient in the late Noachian, the maximum temperature of diagenesis would have been approximately 75 C. This is comparable to shallow burial diagenetic conditions on Earth. The cementation and recrystallization components of lithification are closely intertwined. Cementation describes the precipitation of minerals between grains from pore fluids, and recrystallization (or authigenesis) is when the original sedimentary mineral grains are altered into secondary minerals. The presence of authigenic smectites and magnetite in the YKB formation suggests that some recrystallization has taken place. The relatively high percentage of XRD-amorphous material (25-40%) detected by CheMin suggests that this recrystallization may be limited in scope, and therefore may not contribute significantly to the cementing material. However, relatively persistent amorphous components could exist in the Martian environment (e.g. amorphous MgSO4), so recrystallization, including loss of crystallinity, cannot yet be excluded as a method of cementation. In order to describe the rock cementation, both the rock textures and their composition must be considered. Here, we attempt to summarize the current understanding of the textural and compositional aspects of the cement across the rocks analyzed by Curiosity to this point.

Siebach, K. L.↗

NASA NTRS2015

Martian Chlorobenzene Identified by Curiosity in Yellowknife Bay: Evidence for the Preservation of Organics in a Mudstone on Mars

The Sample Analysis at Mars (SAM) instrument on the Curiosity rover is designed to determine the inventory of organic and inorganic volatiles thermally evolved from solid samples using a combination of evolved gas analysis (EGA), gas chromatography mass spectrometry (GCMS), and tunable laser spectroscopy. The first sample analyzed by SAM at the Rocknest (RN) aeolian deposit revealed chlorohydrocarbons derived primarily from reactions between a martian oxychlorine phase (e.g. perchlorate) and terrestrial carbon from N-methyl-N-(tert-butyldimethylsilyl) trifluoroacetamide (MTBSTFA) vapor present in the SAM instrument background. No conclusive evidence for martian chlorohydrocarbons in the RN sand was found. After RN, Curiosity traveled to Yellowknife Bay and drilled two holes separated by 2.75 m designated John Klein (JK) and Cumberland (CB). Analyses of JK and CB by both SAM and the CheMin x-ray diffraction instrument revealed a mudstone (called Sheepbed) consisting of approx.20 wt% smectite clays, which on Earth are known to aid the concentration and preservation of organic matter. Last year at LPSC we reported elevated abundances of chlorobenzene (CBZ) and a more diverse suite of chlorinated hydrocarbons including dichloroalkanes in CB compared to RN, suggesting that martian or meteoritic organic compounds may be preserved in the mudstone. Here we present SAM data from additional analyses of the CB sample and of Confidence Hills (CH), another drill sample collected at the base of Mt. Sharp. This new SAM data along with supporting laboratory analog experiments indicate that most of the chlorobenzene detected in CB is derived from martian organic matter preserved in the mudstone.

Curiosity in Yellowknife↗

NASA NTRS2013

In-Situ Operations and Planning for the Mars Science Laboratory Robotic Arm: The First 200 Sols

The Robotic Arm (RA) has operated for more than 200 Martian solar days (or sols) since the Mars Science Laboratory rover touched down in Gale Crater on August 5, 2012. During the first seven months on Mars the robotic arm has performed multiple contact science sols including the positioning of the Alpha Particle X-Ray Spectrometer (APXS) and/or Mars Hand Lens Imager (MAHLI) with respect to rocks or loose regolith targets. The RA has supported sample acquisition using both the scoop and drill, sample processing with CHIMRA (Collection and Handling for In- Situ Martian Rock Analysis), and delivery of sample portions to the observation tray, and the SAM (Sample Analysis at Mars) and CHEMIN (Chemistry and Mineralogy) science instruments. This paper describes the planning and execution of robotic arm activities during surface operations, and reviews robotic arm performance results from Mars to date.

Mars surface operations↗

NASA NTRS2015

X-Ray Amorphous Phases in Antarctica Dry Valley Soils: Insight into Aqueous Alteration Processes on Mars?

The Chemistry and Mineralogy (CheMin) instrument onboard the Mars Curiosity rover has detected abundant amounts (approx. 25-30 weight percentage) of X-ray amorphous materials in a windblown deposit (Rocknest) and in a sedimentary mudstone (Cumberland and John Klein) in Gale crater, Mars. On Earth, X-ray amorphous components are common in soils and sediments, but usually not as abundant as detected in Gale crater. One hypothesis for the abundant X-ray amorphous materials on Mars is limited interaction of liquid water with surface materials, kinetically inhibiting maturation to more crystalline phases. The objective of this study was to characterize the chemistry and mineralogy of soils formed in the Antarctica Dry Valleys, one of the driest locations on Earth. Two soils were characterized from different elevations, including a low elevation, coastal, subxerous soil in Taylor Valley and a high elevation, ultraxerous soil in University Valley. A variety of techniques were used to characterize materials from each soil horizon, including Rietveld analysis of X-ray diffraction data. For Taylor Valley soil, the X-ray amorphous component ranged from about 4 weight percentage in the upper horizon to as high as 15 weight percentage in the lowest horizon just above the permafrost layer. Transmission electron microscopy indicated that the presence of short-range ordered (SRO) smectite was the most likely candidate for the X-ray amorphous materials in the Taylor Valley soils. The SRO smectite is likely an aqueous alteration product of mica inherited from granitic materials during glaciation of Taylor Valley. The drier University Valley soils had lower X-ray amorphous contents of about 5 weight percentage in the lowest horizon. The X-ray amorphous materials in University Valley are attributed to nanoparticles of TiO2 and possibly amorphous SiO2. The high abundance of X-ray amorphous materials in Taylor Valley is surprising for one of the driest places on Earth. These materials may have been physically and chemical altered during soil formation, however, the limited interaction with water and low temperatures may result in the formation of "immature" X-ray amorphous or SRO materials. Perhaps, a similar process contributes to the formation of the high content of X-ray amorphous materials detected on Mars.

Ming, D. W.↗

NASA NTRS2014

The Search for Organic Compounds of Martian Origin in Gale Crater by the Sample Analysis at Mars (SAM) Instrument on Curiosity

One of the key objectives of the Mars Science Laboratory rover and the Sample Analysis at Mars (SAM) instrument suite is to determine the inventory of organic and inorganic volatiles in the atmosphere and surface regolith and rocks to help assess the habitability potential of Gale Crater. The SAM instrument on the Curiosity rover can detect volatile organic compounds thermally evolved from solid samples using a combination of evolved gas analysis (EGA) and gas chromatography mass spectrometry (GCMS) (Mahaffy et al. 2012). The first solid samples analyzed by SAM, a scoop of windblown dust and sand at Rocknest, revealed several chloromethanes and a C4-chlorinated hydrocarbon derived primarily from reactions between a martian oxychlorine phase (e.g. perchlorate) and terrestrial carbon from N-methyl-N-(tertbutyldimethylsilyl)- trifluoroacetamide (MTBSTFA) vapor present in the SAM instrument background (Glavin et al. 2013). After the analyses at Rocknest, Curiosity traveled to Yellowknife Bay and drilled two separate holes in a fluvio-lacustrine sediment (the Sheepbed unit) designated John Klein and Cumberland. Analyses of the drilled materials by both SAM and the CheMin X-Ray Diffraction instrument revealed a mudstone consisting of ~20 wt% smectite clays (Ming et al. 2013; Vaniman et al. 2013), which on Earth are known to aid the concentration and preservation of organic matter. Oxychlorine compounds were also detected in the Sheepbed mudstone during pyrolysis; however, in contrast to Rocknest, much higher levels of chloromethanes were released from the Sheepbed materials, suggesting an additional, possibly martian source of organic carbon (Ming et al. 2013). In addition, elevated abundances of chlorobenzene and a more diverse suite of chlorinated alkanes including dichloropropane and dichlorobutane detected in Cumberland compared to Rocknest suggest that martian or meteoritic organic carbon sources may be preserved in the mudstone (Freissinet et al. 2013). Chloromethane and dichloromethane were also identified after thermal volatilization of the surface soils by the GCMS instruments at the Viking landing sites, although no other chlorinated hydrocarbons were reported (Biemann et al. 1977). Here we focus on the origin of the chlorinated hydrocarbons detected in the Sheepbed mudstone by SAM and the implications for the preservation of organic matter in near-surface materials on Mars.

Mars Curiosity Rover↗

NASA NTRS2015

Evidence for Acid-Sulfate Alteration in the Pahrump Hills Region, Gale Crater, Mars

The Pahrump Hills region of Gale crater is a approximately 12 millimeter thick section of sedimentary rock in the Murray formation, interpreted as the basal geological unit of Mount Sharp. The Mars Science Laboratory, Curiosity, arrived at the Pahrump Hills in September 2014 and performed a detailed six-month investigation of the sedimentary structures, geochemistry, and mineralogy of the area. During the campaign, Curiosity drilled and delivered three mudstone samples (targets Confidence Hills, Mojave 2, and Telegraph Peak) to its internal instruments, including the CheMin XRD/XRF.

Rampe, E. B.↗

NASA NTRS2016

Synthesis of Akaganeite in the Presence of Sulfate: Implications for Akaganeite Formation in Yellowknife Bay, Gale Crater, Mars

Akaganeite (beta-FeOOH) is an Fe(III) (hydr)oxide with a tunnel structure usually occupied by chloride. Akaganeite has been recently discovered in a mudstone on the surface of Mars by the Chemistry and Mineralogy (CheMin) and Sample Analysis at Mars (SAM) instruments onboard the Mars Science Laboratory (MSL) Curiosity Rover in Gale crater [1, 2]. Akaganeite was detected together with sulfate minerals [anhydrite (CaSO4) and basanite (2CaSO4·2H2O)] in the drilled Cumberland and John Clein mudstone samples at Yellowknife Bay [2]. Discovery of akaganeite and sulfates in the same samples suggests that sulfate ions could be present in aqueous solution during akaganeite formation. However, mechanism and aqueous environmental conditions of akaganeite formation (e.g., pH and range of sulfate concentration) in Yellowknife Bay remain unknown. The objective of our work was to perform synthesis of akaganeite without or with sulfate addition at variable pHs in order to constrain formation conditions of akaganeite in Yellowknife Bay, Gale crater on Mars.

Peretyazhko, T. S.↗

NASA NTRS2016

Cementation and Aqueous Alteration of a Sandstone Unit Under Acidic Conditions in Gale Crater, Mars

The Curiosity rover landed on Mars in August 2012 to explore the sedimentary history and to assess the habitability of Gale Crater. After 1200 sols of surface operations and over 12 km of traverse distance, the mineralogy of 10 samples has been determined by the CheMin X-ray diffractometer (XRD) and the chemical composition of nearly 300 targets has been established by the Alpha Particle X-ray Spectrometer (APXS). Light-toned fracture zones containing elevated concentrations of silica have been studied by Curiosity's instruments to determine the nature of the fluids that resulted in the enrichment of SiO2. Multiple fluid exposures are evident, and the chemistry and mineralogy data indicate at least two aqueous episodes may have occurred under acidic conditions.

Yen, A. S.↗