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The effects of high concentration of point defects in crystalline ZrSiO4 as originated by exposure to radiation, have been simulated using first principles density functional calculations. Structural relaxation and vibrational studies were performed for a catalogue of intrinsic point defects, with different charge states and concentrations. The experimental evidence of a large anisotropic volume swelling in natural and artificially irradiated samples is used to select the subset of defects that give similar lattice swelling for the concentrations studied, namely interstitials of O and Si, and the anti-site Zr(Si), Calculated vibrational spectra for the interstitials show additional evidence for the presence of high concentrations of some of these defects in irradiated zircon., Comment: 9 pages, 7 (color) figures

Siderite (FeCO3) has been detected in Gale Crater for the first time by the Mars Science Laboratory (MSL) Curiosity and is seen in multiple samples in the Glen Torridon (GT) region. The identification of siderite is based on evolved gas analysis (EGA) data from the Sample Analysis at Mars (SAM) instrument and X-ray diffraction (XRD) data from the Chemistry and Mineralogy (CheMin) instrument. Curiosity descended off of the Vera Rubin ridge (VRR) into the Glen Torridon region on Sol 2300. Glen Torridon is of particular interest because a strong clay mineral signature had been detected by orbital instruments [1]. To date, four drilled samples have been collected at two different drill locations: Kilmarie and Aberlady from adjacent blocks at the base of the south side of VRR in the Jura member and Glen Etive 1 and 2 on the same block in the Knockfarril member.

The asteroids Ryugu and Bennu have spectral characteristics in common with CI/CM type carbonaceous chondrites and are target bodies for JAXA’s Hayabusa2 and NASA’s OSIRIS-Rex missions, respectively. Analog studies, based primarily on the Murchison CM2 chondrite, provide a pathway to separate spectral properties resulting space weathering from those inherent to parent-body, mineralogy, chemistry, and processes. Ryugu shares spectral properties with thermally metamorphosed and partly dehydrated CI/CM chondrites. We have undertaken a multidisciplinary study of the thermal decomposition of Murchison powder samples as an analog to metamorphic process that may have occurred on Ryugu. Bulk analyses include thermal And evolved gas analysis, X-ray diffraction (XRD), and VIS-NIR and Mössbauer spectroscopy; micro- to nanoscale analyses included scanning and transmission electron microscopy and electron probe micro analysisWe report here XRD and VIS-NIR analyses of pre- and post-heated Murchison powders, and in a companion paper report results from multiple electron beam techniques.

Perchlorate was first detected on Mars by the Wet Chemistry Laboratory (WCL) instrument on the Phoenix lander at a concentration of ~0.5 wt% in northern plains soils. Since that initial detection, perchlorate (and likely chlorate) have been detected on Mars by both surface and orbital instruments. Perchlorate (ClO4-) is an oxidized chlorine compound and salts of perchlorate are kinetically stable (though very reactive at high temperature), very soluble, deliquescent, and have low eutectic temperature (which decreases the temperature for stable liquids on Mars). Chlorate (ClO3-) salts are similar, though they are less kinetically stable than perchlorates. Because many of the analytical signatures of perchlorate and chlorate are similar to the instruments we have used on Mars, we cannot always determine which species is present, so we will use the more generic term “oxychlorine” when referring to perchlorate and/or chlorate.

The Sample Analysis at Mars (SAM) instrument on the Mars Science Laboratory (MSL) rover Curiosity has analyzed 3 scooped samples and 15 drilled samples since landing in 2012. Oxychlorine compounds (perchlorate/chlorate) were detected in the first 9 drilled samples but have not been detected in the last 6, starting with the Oudam sample in the Hartmann’s Valley member of the Murray formation (Table 1). Scooped samples have all contained detectable oxychlorine. These results suggest that oxychlorine formation and preservation spans the geologic record on Mars but has not been uniform spatially or temporally.

The Phoenix Scout Lander mission investigated the north polar region of Mars in 2008 with the goal to study the history of water, assess the past/present Martian climate, search for organics, and evaluate the potential for past/present microbial habit-ability on Mars. To accomplish this goal, the Phoenix Lander’s Thermal and Evolved-Gas Analyzer (TEGA) instrument assessed the gas composition of the Martian atmosphere and evaluated the mineralogy of the Martian regolith. The TEGA instrument consisted of eight small ovens connected to a 4 channel magnetic sector mass spectrometer. The ovens heated soil samples from ambient to 1000°C where the gases (e.g., H2O, CO2, etc.) evolved from thermal decomposition of mineral phases were analyzed by the mass spectrometer. Minerals thermally decomposed at characteristic temperatures and the evolving gases indicated the presence of perchlorate, carbonate, and hydrated phases in the Phoenix landing site soils.

The Johnson Space Center Rocknest (JSC-RN) simulant was developed in response to a need by NASA's Advanced Exploration Systems (AES) In Situ Resource Utilization (ISRU) project for a simulant to be used in component and system testing for water extraction from Mars regolith. JSC-RN was de-signed to be chemically and mineralogically similar to material from the aeolian sand shadow named Rocknest in Gale Crater, particularly the 1-3 weight percentage water release as measured by the Sample Analysis at Mars (SAM) instrument. Rocknest material is a proxy for average martian soils, which are unconsolidated and could be easily scooped by rovers or landers in order to extract water. One way in which water can be extracted from aeolian material is through heating, where adsorbed and structural water is thermally removed from minerals. The water can then be condensed and used as drinking water or split and used as propellant for spacecraft or as a source of breathable O2. As such, it was essential that JSC-RN contained evolved gas profiles, especially low temperature water (less than 400 degrees Centigrade), that mimicked what is observed in martian soils. Because many of these ISRU tests require hundreds of kilograms of Mars soil simulant, it was essential that JSC-RN be cost-effective and based on com-ponents that could be purchased commercially (i.e., not synthesized in the lab). Here, we describe the JSC-RN martian soil simulant, which is ideal for large-scale production and use in ISRU water extraction studies.

The Murray formation is predominantly composed of lacustrine mudstone that forms the basal layer of Aeolis Mons (informally Mt. Sharp) in Gale Crater, Mars. The Murray formation has distinct iron and sulfur mineralogical variation within its stratigraphy detectable by the Chemistry Mineralogy (Che-Min) instrument consisting of magnetite/hematite in the lower Murray and higher hematite, CaSO4, and smectite content in the upper Murray. The objectives of this work were to evaluate the Sample Analysis at Mars Evolved Gas Analyzer (SAM-EGA) data to 1) Determine what SAM-EGA-detectable phases correlate or do not correlate with the Murray mineralogical composition detected by CheMin and 2) Utilize CheMin/SAM results to propose possible formation scenarios for the observed Murray mudstone mineralogy.

The Sample Analysis at Mars (SAM) instrument suite on the Mars Science Laboratory (MSL) rover has been essential in understanding volatile-bearing phases in Gale Crater materials. SAM’s evolved gas analysis mass spectrometry (EGA-MS) has detected H2O, CO2, O2, H2, SO2, H2S, HCl, NO, and other trace gases, including organic fragments, in many samples. The identity and evolution temperature of evolved gases can support CheMin instrument mineral detection and place constraints on trace volatile-bearing phases or phases difficult to characterize with X-ray diffraction (e.g., amorphous phases). For the past ~500 sols, MSL has been exploring the Vera Rubin Ridge (VRR), which exhibits a striking hematite signature in orbital remote sensing data, in order to understand the depositional and diagenetic history recorded in the rocks and how it relates to the underlying Murray Formation. Four rock samples were drilled, one from the Blunts Point Member (Duluth, DU), one from the Pettegrrove Point Member (Stoer, ST), and two from the Jura Member. The Jura Member displays differences in color, summarized as grey and red, and a key goal was to constrain the cause of this color difference and the associated implications for depositional or post-depositional conditions. To investigate, a grey (Highfield, HF) and a red (Rock Hall, RH) Jura sample were drilled. Here we will give an overview of results from SAM EGA-MS analyses of VRR materials, with some comparisons to analyses of samples of the underlying Murray.

The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft collected data that provided important insights into the structure, chemical makeup, and compositional diversity of Mercury. Among the many discoveries about Mercury made by MESSENGER, several surprising compositional characteristics of the surface were observed. These discoveries include elevated sulfur abundances (up to 4 wt.%), elevated abundances of graphitic carbon (0-4.1 wt.% across the surface with an additional 1-3 wt.% graphite above the global average in low reflectance materials), low iron abundances (less than 2 wt.%), and low oxygen abundances (O/Si weight ratio of 1.20+/-0.1). These exotic characteristics likely have important implications for the thermochemical evolution of Mercury and point to a planet that formed under highly reducing conditions. In the present study, we focus specifically on the low O/Si ratio of Mercury, which is anomalous compared to all other planetary materials. A recent study that considered the geochemical implications of the low O/Si ratio reported that 12-20% of the surface materials on Mercury are composed of Si-rich, Si-Fe alloys. They further postulated that the origin of the metal is best explained by a combination of space weathering and graphite-induced smelting that was facilitated by interaction of graphite with boninitic and komatiitic parental liquids. The goal of the present study is to assess the plausibility of smelting on Mercury through experiments run at the conditions that McCubbin et al. indicated would be favorable for Si-smelting.

The Mars Science Laboratory rover, Curiosity, is exploring the lowermost formation of Gale crater's central mound. Within this formation, three samples named Marimba, Quela, and Sebina have been analyzed by the CheMin X-ray diffractometer and the Alpha Particle X-ray Spectrometer (APXS) to determine mineralogy and bulk elemental chemistry, respectively. Marimba and Quela were also analyzed by the SAM (Sample Analysis at Mars) instrument to characterize the type and abundance of volatile phases detected in evolved gas analyses (EGA). CheMin data show similar proportions of plagioclase, hematite, and Ca-sulfates along with a mixture of di- and trioctahedral smectites at abundances of approximately 28, approximately 16, and approximately 18 wt% for Marimba, Quela, and Sebina. Approximately 50 wt% of each mudstone is comprised of X-ray amorphous and trace crystalline phases present below the CheMin detection limit (approximately 1 wt%). APXS measurements reveal a distinct bulk elemental chemistry that cannot be attributed to the clay mineral variation alone indicating a variable amorphous phase assemblage exists among the three mudstones. To explore the amorphous component, the calculated amorphous composition and SAM EGA results are used to identify amorphous phases unique to each mudstone. For example, the amorphous fraction of Marimba has twice the FeO wt% compared to Quela and Sebina yet, SAM EGA data show no evidence for Fe-sulfates. These data imply that Fe must reside in alternate Fe-bearing amorphous phases (e.g., nanophase iron oxides, ferrihydrite, etc.). Constraining the composition, abundances, and proposed identity of the amorphous fraction provides an opportunity to speculate on the past physical, chemical, and/or diagenetic processes which produced such phases in addition to sediment sources, lake chemistry, and the broader geologic history of Gale crater.

While hydrogen peroxide (H2O2) has been detected in the martian atmosphere, it has not been detected in surface materials. Since the Viking lander mission, we have sent instruments to Mars with the capability to detect H2O2. The Sample Analysis at Mars (SAM) instrument onboard the Curiosity Rover and Thermal and Evolved Gas Analyzer (TEGA) instrument on the Phoenix lander both detected water and oxygen releases from analyzed sediments but whether or not peroxide could be the source of these gases has not been investigated. We are investigating the possible presence of H2O2 in martian materials by analyzing Mars-relevant minerals that have been mixed with hydrogen peroxide using lab instruments configured as analogs to Mars mission instruments. The object of this research is to use lab instruments to find the effects of Mars analog minerals on hydrogen peroxide gas release temperatures, specifically gas releases of water and oxygen and also determine the effect of the peroxide on the minerals. Data that we get from the lab can then be compared to the data collected from Mars. The minerals hematite, siderite, San Carlos olivine, magnetite and nontronite were chosen as our Mars analog minerals. ~20 mg of analog Mars minerals with 5μl of 50% H2O2, and were either run immediately or placed in a sealed tube for 2, 4, or 9 days to look for changes over time with two reps being done at each time step to determine repeatability. Each sample was heated from -60 degC to 500 degC at 20 degC/min and the evolved gases were monitored with a mass spectrometer. Each sample was also analyzed with an X-ray diffraction instrument to look for changes in mineralogy. Preliminary results show three potential outcomes: 1) peroxide has no effect on the sample (e.g., hematite), 2) the mineral is unaffected but catalyzes peroxide decomposition (magnetite, siderite), or 3) peroxide alters the mineral (pyrrhotite, San Carlos olivine).

Variability in the sulfur isotopic composition in sediments can reflect atmospheric, geologic and biological processes. Evidence for ancient fluvio-lacustrine environments at Gale crater on Mars and a lack of efficient crustal recycling mechanisms on the planet suggests a surface environment that was once warm enough to allow the presence of liquid water, at least for discrete periods of time, and implies a greenhouse effect that may have been influenced by sulfur-bearing volcanic gases. Here we report in situ analyses of the sulfur isotopic compositions of SO2 volatilized from ten sediment samples acquired by NASA's Curiosity rover along a 13 km traverse of Gale crater. We find large variations in sulfur isotopic composition that exceed those measured for Martian meteorites and show both depletion and enrichment in S-34. Measured values of δS-34 range from -47 +/- 14% to 28 +/- 7%, similar to the range typical of terrestrial environments. Although limited geochronological constraints on the stratigraphy traversed by Curiosity are available, we propose that the observed sulfur isotopic signatures at Gale crater can be explained by equilibrium fractionation between sulfate and sulfide in an impact-driven hydrothermal system and atmospheric processing of sulfur-bearing gases during transient warm periods.

Akaganeite (Beta-FeOOH, chloride-containing Fe(III) (hydr)oxide) has been recently discovered on the surface of Mars by the Mars Science Laboratory Curiosity rover in Yellowknife Bay, Gale Crater, Mars [1] and from orbit by the Mars Reconnaissance Orbiter in Robert Sharp crater and Antoniadi basin [2]. However, the mechanism and aqueous environmental conditions of akaganeite formation (e.g., pH and chloride concentration) remain unknown. We have investigated formation of akaganeite through Fe(III) hydrolysis at variable initial pH and chloride concentrations. The formed Fe(III) precipitates were characterized by instruments similar to instruments on Mars robotic spacecraft. Syntheses were performed through hydrolysis of Fe(III) perchlorate with addition of Na cloride (Fe/Cl ratio between 0.5 and 5) and at initial pH of 1.5, 2, 4, 6 and 8 at 90degC. X-ray diffraction analysis revealed formation of akaganeite alone or in mixture with goethite, hematite and ferrihydrite at all initial pHs and Fe/Cl ratio between 0.5 and 2 while akaganeite precipitated only at pH 1.5 and Fe/Cl greater than2. Chloride content of akaganeite was affected by initial pH and decreased from 20-60 mg/g at pH 1.5 to less than 0.1 mg/g at pH 8. The synthesized akaganeite samples were also characterized by Mössbauer and infrared spectroscopy and volatiles were analysed by thermal and evolved gas analysis. The obtained characterization data will be compared to published data from rover and orbital missions [1-3] to determine martian akaganeite composition, crystallinity and formation conditions.

The sample analysis at Mars instrument evolved gas analyzer (SAM-EGA) has detected evolved water, H2, SO2, H2S, NO, CO2, CO, O2, and HCl from two eolian sediments and nine sedimentary rocks from Gale Crater, Mars. These evolved gas detections indicate nitrates, organics, oxychlorine phase, and sulfates are widespread with phyllosilicates and carbonates occurring in select Gale Crater materials. Coevolved CO2 (160 +/- 248-2373 +/- 820 μgC(CO2)/g) and CO (11 +/- 3-320 +/- 130 μgC(CO)/g) suggest that organic C is present in Gale Crater materials. Five samples evolved CO2 at temperatures consistent with carbonate (0.32 +/- 0.05-0.70 +/- 0.1 wt % CO3). Evolved NO amounts to 0.002 +/- 0.007-0.06 +/- 0.03 wt % NO3. Evolution of O2 suggests that oxychlorine phases (chlorate/perchlorate) (0.05 +/- 0.025-1.05 +/- 0.44 wt % ClO4) are present, while SO2 evolution indicates the presence of crystalline and/or poorly crystalline Fe and Mg sulfate and possibly sulfide. Evolved H2O (0.9 +/- 0.3-2.5 +/- 1.6 wt % H2O) is consistent with the presence of adsorbed water, hydrated salts, interlayer/structural water from phyllosilicates, and possible inclusion water in mineral/amorphous phases. Evolved H2 and H2S suggest that reduced phases occur despite the presence of oxidized phases (nitrate, oxychlorine, sulfate, and carbonate). SAM results coupled with CheMin mineralogical and Alpha-Particle X-ray Spectrometer elemental analyses indicate that Gale Crater sedimentary rocks have experienced a complex authigenetic/diagenetic history involving fluids with varying pH, redox, and salt composition. The inferred geochemical conditions were favorable for microbial habitability and if life ever existed, there was likely sufficient organic C to support a small microbial population.

Clay minerals have been identified on Mars' oldest (Noachian) terrain and their presence suggests long-term water-rock interactions. The most commonly identified clay minerals on Mars to date are nontronite (Fe-smectite) and montmorillonite (Al-smectite) [1], both of which contain variable amounts of water both adsorbed on their surface and within their structural layers. Over Mars' history, these clay miner-al-water assemblages may have served as nutrient sources for microbial life.

The Sample Analysis at Mars (SAM) instrument on board the Curiosity Rover has detected high temperature water releases from mud-stones in the areas of Yellowknife Bay, Pahrump Hills, Naukluft Plateau, and Murray Buttes in Gale crater. Dehydroxylation of phyllosilicates may have caused the high temperature water releases observed in these samples. Because each type of phyllosilicate undergoes dehydroxylation at distinct temperatures, these water releases can be used to help constrain the type of phyllosilicate present in each sample.

One among the main objectives of the Sample Analysis at Mars (SAM) experiment is the in situ molecular analysis of gases evolving from solid samples heated up to approximately 850 degrees Centigrade, and collected by Curiosity on Mars surface/sub-surface in Gale crater. With this aim, SAM uses a gas-chromatograph coupled to a quadrupole mass spectrometer (GC-QMS) devoted to separate, detect and identify both volatile inorganic and organic compounds. SAM detected chlorinated organic molecules produced in evolved gas analysis (EGA) experiments. Several of these were also detected by the Viking experiments in 1976. SAM also detected oxychlorine compounds that were present at the Phoenix landing site. The oxychlorines may be prevelant over much of the martian surface. The C1 to C3 aliphatic chlorohydrocarbons (chloromethane and di- and trichloromethane) detected by SAM were attributed to reaction products occurring between the oxychlorines phases and the organic compounds coming from SAM instrument background. But SAM also showed the presence of a large excess of chlorobenzene and C2 to C4 dichloroalkanes among the volatile species released by the Cumberland sample of the Sheepbed mudstone. For the first time in the history of the Mars exploration, this proved the presence of Mars indigenous organic material at the Mars' surface. However, the identification of the precursor organic compounds of these chlorohydrocarbons is difficult due to the complexity of the reactions occurring during the sample pyrolysis. Laboratory pyrolysis experiments have demonstrated that oxychlorines phases such as perchlorates and chlorates, decomposed into dioxygen and volatile chlorine bearing molecules (HCl and/or Cl2) during the pyrolysis. These chemical species can then react with the organic molecules present in the martian solid samples through oxidation, chlorination and oxychlorination processes.

The Sample Analysis at Mars (SAM) instrument aboard the Mars Science Laboratory rover has analyzed 13 samples from Gale Crater. All SAM-evolved gas analyses have yielded a multitude of volatiles (e.g., H2O, SO2, H2S, CO2, CO, NO, O2, HCl) [1- 6]. The objectives of this work are to 1) Characterize recent evolved SO2, CO2, O2, and NO gas traces of the Murray formation mudstone, 2) Constrain sediment mineralogy/composition based on SAM evolved gas analysis (SAM-EGA), and 3) Discuss the implications of these results relative to understanding the geological history of Gale Crater.

The Mars Science Laboratory (MSL) Curiosity rover recently traversed over plateaus of mafic aeolian sandstones (the 'Stimson' formation) that overlie mudstones (the 'Murray' formation). Within the Stimson formation we observed many lighter-toned, halo-forming features, that are potentially indicative of fluid alteration (see Fig. 1). These halo features extend for tens of meters laterally and are approx.1 meter wide. The halo features were characterized by Curiosity's geochemical instruments: Alpha Proton X-Ray Spectrometer (APXS), Chemin, Chemcam and Sample Analysis at Mars (SAM). With respect to the host (unaltered) Stimson rocks, fracture halos were significantly enriched in silicon and low in iron [1]. Changes in hydrogen abundance (due to its large neutron scattering cross section) greatly influence the magnitude of the thermal neutron response from the Dynamic Albedo of Neutrons (DAN) instrument [2]. There are also some elemental species, e.g. chlorine, iron, and nickel, that have significant microscopic neutron absorption cross sections. These elements can be abundant and variable results provide a useful estimate of the lower bound for bulk hydrogen content (assuming a homogeneous distribution).

The Sample Analysis at Mars (SAM) and Chemistry and Mineralogy (CheMin) instruments on the Mars Science Laboratory (MSL) have analysed more than 150 micron fines from 14 sites at Gale Crater. Here we focus on the mudstone samples. Two were drilled from sites John Klein (JK) and Cumberland (CB) in the Sheepbed mudstone. Six were drilled from Murray Formation mudstone: Confidence Hills (CH), Mojave (MJ), Telegraph Peak (TP), Buckskin (BK), Oudam (OU), Marimba (MB). SAM's evolved gas analysis mass spectrometry (EGA-MS) detected H2O, CO2, O2, H2, SO2, H2S, HCl, NO, and other trace gases, including organic fragments. The identity and evolution temperature of evolved gases can support CheMin mineral detection and place constraints on trace volatile-bearing phases or phases difficult to characterize with X-ray diffraction (e.g., amorphous phases). Here we will focus on SAM H2O data and comparisons to SAM-like analyses of key reference materials.

The Sample Analysis at Mars (SAM) instrument has detected evolved O2 and HCl indicating the presence of perchlorate and/or chlorate (oxychlorine) in all 11 sediments analyzed to date. The hyperarid martian climate is believed to have allowed accumulation of oxychlorine and assumed chloride contents similar to those in hyperarid terrestrial settings. The linear correlation of oxychlorine and chloride of Gale Crater sediments is low (r (sup 2) equals 0.64). Correlations present in hyperarid Antarctica and the Atacama Desert are attributed to unaltered atmospheric source coupled with minimal redox cycling by biological activity. Terrestrial semi-arid to arid settings have low correlations similar to Gale Crater and are attributed to additional inputs of Cl minus from sea salt, dust, and/or proximal playa settings, and possible reduction of oxychlorine phases during wetter periods. While microbiological processes could contribute to low oxychlorine/chloride correlations on Mars, several abiotic mechanisms are more likely, such as changing oxychlorine production rates with time and/or post-depositional geochemical redox processes that altered the Gale Crater oxychlorine and chloride contents.

The Sample Analysis at Mars (SAM) and Chemistry and Mineralogy (CheMin) instruments on the Mars Science Laboratory (MSL) have analyzed several subsamples of <150 micron fines from ten sites at Gale Crater. Three were in Yellowknife Bay: the Rocknest aeolian bedform (RN) and drilled Sheepbed mudstone from sites John Klein (JK) and Cumberland (CB). One was drilled from the Windjana (WJ) site on a sandstone of the Kimberly formation. Four were drilled from sites Confidence Hills (CH), Mojave (MJ), Telegraph Peak (TP) and Buckskin (BK) of the Murray Formation at the base of Mt. Sharp. Two were drilled from sandstones of the Stimson formation targeting relatively unaltered (Big Sky, BY) and then altered (Greenhorn, GH) material associated with a light colored fracture zone. CheMin analyses provided quantitative sample mineralogy. SAM's evolved gas analysis mass spectrometry (EGA-MS) detected H2O, CO2, O2, H2, SO2, H2S, HCl, NO, and other trace gases. This contribution will focus on evolved SO2. All samples evolved SO2 above 500 C. The shapes of the SO2 evolution traces with temperature vary between samples but most have at least two "peaks' within the wide high temperature evolution, from approx. 500-700 and approx. 700-860 C (Fig. 1). In many cases, the only sulfur minerals detected with CheMin were Ca sulfates (e.g., RN and GH), which should thermally decompose at temperatures above those obtainable by SAM (>860 C). Sulfides or Fe sulfates were detected by CheMin (e.g., CB, MJ, BK) and could contribute to the high temperature SO2 evolution, but in most cases they are not present in enough abundance to account for all of the SO2. This additional SO2 could be largely associated with x-ray amorphous material, which comprises a significant portion of all samples. It can also be attributed to trace S phases present below the CheMin detection limit, or to reactions which lower the temperatures of SO2 evolution from sulfates that are typically expected to thermally decompose at temperatures outside the SAM temperature range (e.g., Ca and Mg sulfates). Here we discuss the results of SAM-like laboratory analyses targeted at understanding this last possibility, focused on understanding if reactions of HCl or an HCl evolving phase (oxychlorine phases, chlorides, etc.) and Ca and Mg sulfates can result in SO2 evolution in the SAM temperature range.

The Sample Analysis at Mars (SAM) instrument on board the Curiosity Rover has detected oxygen and HCl gas releases from all analyzed Gale Crater sediments. The presence of perchlorate ClO4(sup-) and/or chlorates ClO3(sup-) are potential sources of the aforementioned O2 releases. The detections of O2 and HCl gas releases and chlorinated hydrocarbons by SAM coupled with the detection of perchlorates by Phoenix Lander's 2008 Wet Chemistry Laboratory all suggest that perchlorates, and possibly chorates, may be present in the Gale Crater sediments. Previous laboratory studies have attempted to replicate these O2 releases by heating perchlorates and chlorates in instruments operated similarly to those in the SAM instrument. Early studies found that pure perchlorates release O2 at temperatures higher than those observed in SAM data. Subsequently, studies were done to test the effects of mixing iron-phase minerals, analogous to those detected on Mars by ChemMin, with perchlorates. The iron in these minerals acts as a catalyst and causes O2 to be released from the perchlorate at a lower temperature. These studies found that perchlorate solutions mixed with either Hawaii palagonite or ferrihydrite produce O2 releases at temperatures similar to the Rocknest (RN) windblown deposit and the John Klein (JK) drill sample from the Sheepbed mudstone. The study also determined that perchlorate mixtures with magnetite, hematite, fayalite-magnetite, ilmentite, and pyrrhotite produce O2 releases at temperatures similar to the Confidence Hills (CH) drill sample from the Murray mudstone. Oxygen re-leases from pure chlorates were recently compared with the SAM data. Laboratory analyses determined that Ca-chlorate produces O2 and HCl peaks that are similar to those detected in RN and JK materials. Currently, no perchlorate/chlorate mixture with iron-phase minerals can explain the O2 releases from either the Cumberland (CB) drill sample from the Sheepbed mudstone or Windjana (WJ) drill sample from the Kimberly sandstone. Mixtures of chlorate solutions with iron-phase minerals may produce O2 peaks at temperatures that match those from CB and WJ materials. The goal of this work is to determine if heating chlorate solutions mixed with iron-phase minerals will produce O2 and HCl peak temperatures similar to O2 and HCl peak temperatures of sediments analyzed by SAM, particularly the WJ and CB materials.

The Sample Analysis at Mars (SAM) instrument onboard Curiosity can perform pyrolysis of martian solid samples, and analyze the volatiles by direct mass spectrometry in evolved gas analysis (EGA) mode, or separate the components in the GCMS mode (coupling the gas chromatograph and the mass spectrometer instruments). In addition, SAM has a wet chemistry laboratory designed for the extraction and identification of complex and refractory organic molecules in the solid samples. The chemical derivatization agent used, N-methyl-N-tert-butyldimethylsilyl- trifluoroacetamide (MTBSTFA), was sealed inside seven Inconel metal cups present in SAM. Although none of these foil-capped derivatization cups have been punctured on Mars for a full wet chemistry experiment, an MTBSTFA leak was detected and the resultant MTBSTFA vapor inside the instrument has been used for a multi-sol MTBSTFA derivatization (MD) procedure instead of direct exposure to MTBSTFA liquid by dropping a solid sample directly into a punctured wet chemistry cup. Pyr-EGA, Pyr-GCMS and Der-GCMS experiments each led to the detection and identification of a variety of organic molecules in diverse formations of Gale Crater.