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NASA NTRS1988

Sulfide mineralization: Its role in chemical weathering of Mars

Pyrrhotite-pentlandite assemblages in mafic and ultramafic igneous rocks may have contributed significantly to the chemical weathering reactions that produced degradation products in the Martian regolith. By analogy with terrestrial processes, a model is proposed whereby supergene alteration of these primary Fe-Ni sulfides on Mars has generated secondary sulfides (e.g., pyrite) below the water table and produced acidic groundwater containing high concentrations of dissolved Fe, Ni and sulfate ions. The low pH solutions also initiated weathering reactions of igneous feldspars and ferromagnesian silicates to form clay silicate and ferric oxyhydroxide phases. Near-surface oxidation and hydrolysis of ferric sulfato- and hydroxo-complex ions and sols formed gossans above the water table consisting of poorly crystalline hydrated ferric sulfates (e.g., jarosite), oxides (ferrihydrite, goethite) and silica (opal). Underlying groundwater, now permafrost, contains hydroxo sulfato complexes of Fe, Al, Mg, Ni, etc., which may be stabilized in frozen acidic solutions beneath the surface of Mars. Sublimation of permafrost may replenish colloidal ferric oxides, sulfates and phyllosilicates during dust storms on Mars.

Burns, Roger G.↗

NASA NTRS1987

Weathering of sulfides on Mars

Pyrrhotite-pentlandite assemblages in mafic and ultramafic igneous rocks may have contributed significantly to the chemical weathering reactions that produce degradation products in the Martian regolith. By analogy and terrestrial processes, a model is proposed whereby supergene alteration of these primary Fe-Ni sulfides on Mars has generated secondary sulfides (e.g., pyrite) below the water table and produced acidic groundwater containing high concentrations of dissolved Fe, Ni, and sulfate ions. The low pH solutions also initiated weathering reactions of igneous feldspars and ferromagnesian silicates to form clay silicate and ferric oxyhydroxide phases. Near-surface oxidation and hydrolysis of ferric sulfato-and hydroxo-complex ions and sols formed gossan above the water table consisting of poorly crystalline hydrated ferric sulfates (e.g., jarosite), oxides (ferrihydrite, goethite), and silica (opal). Underlying groundwater, now permafrost contains hydroxo sulfato complexes of Fe, Al, Mg, Ni, which may be stabilized in frozen acidic solutions beneath the surface of Mars. Sublimation of permafrost may replenish colloidal ferric oxides, sulfates, and phyllosilicates during dust storms on Mars.

Burns, Roger G.↗

NASA NTRS1995

Low-temperature and low atmospheric pressure infrared reflectance spectroscopy of Mars soil analog materials

Infrared reflectance spectra of carefully selected Mars soil analog materials have been measured under low atmospheric pressures and temperatures. Chemically altered montmorillonites containing ferrihydrite and hydrated ferric sulfate complexes are examined, as well as synthetic ferrihydrate and a palagonitic soil from Haleakala, Maui. Reflectance spectra of these analog materials exhibit subtle visible to near-infrared features, which are indicative of nanophase ferric oxides or oxyhydroxides and are similar to features observed in the spectra of the bright regions of Mars. Infrared reflectance spectra of these analogs include hydration features due to structural OH, bound H2O and adsorbed H2O. The spectal character of these hydration features is highly dependent on the sample environment and on the nature of the H2O/OH in the analogs. The behavior of the hydration features near 1.9 micrometers, 2.2 micrometers, 2.7 micrometers, 3 micrometers, and 6 micrometers are reported here in spetra measured under Marslike atmospheric environment. In spectra of these analogs measured under dry Earth atmospheric conditions the 1.9-micrometer band depth is 8-17%; this band is much stonger under moist conditions. Under Marslike atmospheric conditions the 1.9-micrometer feature is broad and barely discernible (1-3% band depth) in spectra of the ferrihydrite and palagonitic soil samples. In comparable spectra of the ferric sulfate-bearing montmorillonite the 1.9-micrometer feature is also broad, but stronger (6% band depth). In the low atmospheric pressure and temperature spectra of the ferrihydrite-bearing montmorillonite this feature is sharper than the other analogs and relatively stronger (6% band depth). Although the intensity of the 3- micrometer band is weaker in spectra of each of the analogs when measured under Marslike conditions, the 3-micromter band remains a dominant feature and is especially broad in spectra of the ferrihydrite and palagonitic soil. The structural OH features observed in these materials at 2.2-2.3 micrometers and 2.27 micrometers remain largely unaffected by the environmental conditions. A shift in the Christiansen feature towards shorter wavelengths has also been observed with decreasing atmospheric pressure and temperature in the midinfrared spectra of these samples.

Bishop, Janice L.↗

NASA NTRS1995

Low-temperature and low atmospheric pressure infrared reflectance spectroscopy of Mars soil analog materials

Infrared reflectance spectra of carefully selected Mars soil analog materials have been measured under low atmospheric pressures and temperatures. Chemically altered montmorillonites containing ferrihydrite and hydrated ferric sulfate complexes are examined, as well as synthetic ferrihydrite and a palagonitic soil from Haleakala, Maui. Reflectance spectra of these analog materials exhibit subtle visible to near-infrared features, which are indicative of nanophase ferric oxides or oxyhydroxides and are similar to features observed in the spectra of the bright regions of Mars. Infrared reflectance spectra of these analogs include hydration features due to structural OH, bound H2O, and adsorbed H2O. The spectral character of these hydration features is highly dependent on the sample environment and on the nature of the H2O/OH in the analogs. The behavior of the hydration features near 1.9 micron, 2.2 micron, 2.7 micron, 3 micron, and 6 microns are reported here in spectra measured under a Marslike atmospheric environment. In spectra of these analogs measured under dry Earth atmospheric conditions the 1.9-micron band depth is 8-17%; this band is much stronger under moist conditions. Under Marslike atmospheric conditions the 1.9-micron feature is broad and barely discernible (1-3% band depth) in spectra of the ferrihydrite and palagonitic soil samples. In comparable spectra of the ferric sulfate-bearing montmorillonite the 1.9-micron feature is also broad, but stronger (6% band depth). In the low atmospheric pressure and temperature spectra of the ferrihydrite-bearing montmorillonite this feature is sharper than the other analogs and relatively stronger (6% band depth). Although the intensity of the 3-micron band is weaker in spectra of each of the analogs when measured under Marslike conditions, the 3-micron band remains a dominant feature and is especially broad in spectra of the ferrihydrite and palagonitic soil. The structural OH features observed in these materials at 2.2-2.3 micron and 2.75 microns remain largely unaffected by the environmental conditions. A shift in the Christiansen feature towards shorter wavelengths has also been observed with decreasing atmospheric pressure and temperature in the midinfrared spectra of these samples.

Bishop, Janice L.↗

NASA NTRS1991

Midinfrared spectral investigations of carbonates: Analysis of remotely sensed data

Recent airborne thermal infrared observations of Mars from the Kuiper Airborne Observatory (KAO) have provided evidence for the presence of carbonates, sulfates, and hydrates. Using the optical properties of calcite and anhydrite, it was estimated that CO3's and SO4's constituted about 1 to 3 and 10 to 15 wt. percent, repectively of the materials composing the atmospheric dust. Using the derived value as an estimate of total CO3 abundance, and making an assumption that the CO3's were uniformly distributed within the Martian regolith, it was estimated that such a CO3 reservoir could contain roughly 2 to 5 bars of CO2. While the results indicate that several volatile-bearing materials are present on Mars, the observations from the KAO are inherently limited in their ability to determine the spatial distributions of these materials. However, previous spacecraft observations of Mars provide both the spectral coverage necessary to identify these materials, as well as the potential for investigating their spatial variability. This has prompted us to pursue a reinvestigation of the Mariner 6 and 7 infrared spectrometer and Mariner 9 infrared interferometer spectrometer observations. The former data have been recently made available in digital format and calibration of wavelengths and intensities are almost complete. Additionally, we are pursuing the derivation of optical constants of more appropriate carbonates and sulfates.

Roush, T.↗

NASA NTRS1975

Feasibility of an advanced thrust termination assembly for a solid propellant rocket motor

A total of 68 quench tests were conducted in a vented bomb assembly (VBA). Designed to simulate full-scale motor operating conditions, this laboratory apparatus uses a 2-inch-diameter, end-burning propellant charge and an insulated disc of consolidated hydrated aluminum sulfate along with the explosive charge necessary to disperse the salt and inject it onto the burning surface. The VBA was constructed to permit variation of motor design parameters of interest; i.e., weight of salt per unit burning surface area, weight of explosive per unit weight of salt, distance from salt surface to burning surface, incidence angle of salt injection, chamber pressure, and burn time. Completely satisfactory salt quenching, without re-ignition, occurred in only two VBA tests. These were accomplished with a quench charge ratio (QCR) of 0.023 lb salt per square inch of burning surface at dispersing charge ratios (DCR) of 13 and 28 lb of salt per lb of explosive. Candidate materials for insulating salt charges from the rocket combustion environment were evaluated in firings of 5-inch-diameter, uncured end-burner motors. A pressed, alumina ceramic fiber material was selected for further evaluation and use in the final demonstration motor.

Source record↗

NASA NTRS1976

Preliminary results from the Viking X-ray fluorescence experiment - The first sample from Chryse Planitia, Mars

Iron, calcium, aluminum, silicon, and sulfur are major elements in the first surface sample of Mars that has been analyzed by the Viking X-ray fluorescence spectrometer. Titanium is present in minor quantities. This is consistent with the sample's being a mixture of fine silicate and oxide mineral grains, with a significant proportion of sulfates, possibly hydrated. Ferric oxide is regarded as the red pigmenting agent on the Martian surface, but if it coats silicate grains, the coatings must be very thin or discontinuous. A high abundance of Fe, relatively low abundances of Al, Rb, Sr, and Zr, and a high Ca/K ratio are distinctive features of the spectra. Preliminary determinations indicate the following abundances (as percentages by weight): Fe, 14 plus or minus 2; Ti, less than 1; S, 2 to 5; the Ca/K ratio by weight is greater than 5.

Toulmin, P., III↗

NASA NTRS1989

Soil developments in polar deserts: Implications for exobiology and future Mars missions

Chemical alterations, weathering, and diagenesis of soil profiles from the dry valleys of Antarctica were studied as analogs of regolith development for the Martian regolith. Chemical weathering processes play an important part in soil development within the dry valleys of Antarctica. A suite of core samples were studied which were taken within the valley floors in addition to samples taken in the vicinity of evaporite and brine ponds. Analysis of water soluable cations and anions from core samples were performed along with petrographic analysis of selected samples. It was shown that ionic transport processes operate primarily above the permafrost zone. Abundances of the water soluable ions reflect the nature of secondary minerals produced by evaporation and weathering. Chloride, calcium, and sodium abundances for soils from the cores within the North and South Forks of Wright Valley, reflect the secondary mineralogy of the soil columns. Calculations for Na, Ca, and Cl abundances reflect the appearance of halite and antarcticite. In areas where excess Ca is present, X-ray diffraction studies show the presence of gypsum. It is well known that the Martian surface conditions may be favorable for chemical weathering. Primary silicates would be expected to be reactive with any ground water. It seems likely that Martian subsurface water is available to assist in the weathering of the primary minerals. Such weathering could result in the formation of clays, sulfates, carbonates, hydrates, halides, and zeolites. The dry valley cores have shown that they maybe excellent analogs to weathering processes on the near-surface of Mars. Since movement of water within the near-surface region clearly results in chemical weathering, leaching, and salt formation in the dry valleys, similar processes are probably operating within the Martian regolith.

Gibson, Everett K., Jr.↗

NASA NTRS1991

Laboratory and field studies of stratospheric aerosols: Phase changes under high supersaturation

It is well known that water in the form of isolated small droplets supercool as much as 40 C below their equilibrium melting point. Solutions similarly supercool (with respect to water) and supersaturate (with respect of the solute). Experiments are described in which bulk solutions typical of atmospheric aerosols (nitric acid, sulfuric acid, and hydrates; ammonium sulfate; ammonium bisulfate; sodium chloride) are supercooled and/or supersaturated and nucleated to initiate crystal growth. Supersaturation of 300 percent is readily attainable, with linear growth of crystals increasing roughly as (supercooling/supersaturation)sup 2. The implication of the experiments is that the situation of metastability in polar stratosphere clouds is very likely, with nucleation only occuring under a high degree of supercooling or supersaturation.

Hallet, John↗

NASA NTRS2000

Identification of Crystalline Minerals in Volcanic Alteration Products and Applications to the Surface of Mars

Visible, infrared and Mossbauer spectra have been measured for fine-grained alteration products of volcanic tephra and ash. Comparison of the spectral and chemical properties for different size separates and related samples provides information about the crystalline materials in these samples and how they may have formed. Hydrothermal processes can increase the alteration rates of the primary minerals and glass and provide S, Fe and/or water for formation of sulfates and hydrated minerals. Identification of crystalline alteration minerals on Mars may indicate hydrothermal alteration and sites of interesting geologic processes.

Bishop, J. L.↗

NASA NTRS2004

Quantitative Mineralogical Analysis of Mars Analogues Using CHEMIN Data and Rietveld Refinement

Mineralogical analysis is a critical component of planetary surface exploration. Chemical data alone leave serious gaps in our understanding of the surfaces of planets where complex minerals may form in combination with H, S, and halogens. On such planets (e.g., Mars) a single chemical composition may represent a range of mineral assemblages. For example, Viking chemical analyses of excavated duricrust indicate that Mg and S are correlated and ~10% MgSO4 (anhydrous weight) is a likely cementing agent. Pathfinder chemical data support a similar abundance of MgSO4 in the most altered materials. However, there are many possible Mg-sulfates with widely varying hydration states (including dehydrated and 1-, 2-, 3-, 4-, 5-, 6-, and 7-hydrates). In addition, other sulfate minerals such as gypsum (CaSO4 .2H2O) and other salts containing Cl may also exist. X-ray diffraction (XRD) has the ability to decipher mixtures of these phases that would be difficult, if not impossible to unravel using only chemical or spectral data.

Bish, D. L.↗

NASA NTRS2008

Gusev Crater on Mars: Wet and Dry

The Mars Exploration Rover Spirit has traversed over 7.5 km in 1470 sols of operations at the Gusev Crater landing site. Chemical and mineralogical evidence from approximately 200 in-situ samples indicate various degrees of exposure to liquid water, from wet and saturated to dry and unaltered. (1) Six samples with concentrations of amorphous silica between 60 and 95 wt% were discovered in a small valley less than 50 meters in length. Associated enrichments in titanium oxide, relatively insoluble at low pH, suggest that these silica deposits formed as a result of acidic leaching processes. Liquid water interactions with these surface materials were necessary to remove cations solubilized in the low pH environment or to concentrate silica in solution prior to precipitation. (2) Hydrated ferric sulfates are found in subsurface deposits which have the unmistakable chemical signatures of nearby rocks. The movement of hydrothermal fluids and/or fumarolic vapors through local rocks prior to precipitation of these materials is suggested by these observations. (3) Goethite (alpha-FeOOH), a mineral phase which requires water to form, represents 20% to 35% of the iron in numerous rock samples (Clovis Class) on the West Spur of the Columbia Hills. Alteration of iron under aqueous conditions is clearly indicated by this presence of goethite. (4) Nearly isochemical signatures are found in elemental analyses of over ten distinct samples (Wishstone/Watchtower class rocks), yet the ratio of ferric iron to total iron varies from 0.4 to 0.95. Small quantities of water, insufficient to flush cations from the samples, were likely responsible for this weathering. (5) Bromine, a trace element readily mobilized by water, is found in high concentrations in certain rock interiors and is enhanced in subsurface soils, consistent with transport to localized cold traps by water thin-films. (6) Also relevant to the characterizing the role of liquid water is the discovery of an areally extensive ultramafic sequence of rocks where over 70% of the iron is in unaltered olivine and the ferric to total iron ratio is 0.1. This result indicates that certain materials at the martian surface have been protected from aqueous alteration.

Yen, Albert↗

NASA NTRS2009

Evolved Gas Measurements Planned for the Lower Layers of the Gale Crater Mound with the Sample Analysis at Mars Instrument Suite

The lower mound strata of Gale Crater provide a diverse set of chemical environments for exploration by the varied tools of the Curiosity Rover of the Mars Science Laboratory (MSL) Mission. Orbital imaging and spectroscopy clearly reveal distinct layers of hydrated minerals, sulfates, and clays with abundant evidence of a variety of fluvial processes. The three instruments of the MSL Sample Analysis at aMars (SAM) investigation, the Quadrupole Mass Spectrometer (QMS), the Tunable Laser Spectrometer (TLS), and the Gas Chromatograph (GC) are designed to analyze either atmospheric gases or volatiles thermally evolved or chemically extracted from powdered rock or soil. The presence or absence of organic compounds in these layers is of great interest since such an in situ search for this type of record has not been successfully implemented since the mid-60s Viking GCMS experiments. However, regardless of the outcome of the analysis for organics, the abundance and isotopic composition of thermally evolved inorganic compounds should also provide a rich data set to complement the mineralogical and elemental information provided by other MSL instruments. In addition, these evolved gas analysis (EGA) experiments will help test sedimentary models proposed by Malin and Edgett (2000) and then further developed by Milliken et al (2010) for Gale Crater. In the SAM EGA experiments the evolution temperatures of H2O, CO2, SO2, O2, or other simple compounds as the samples are heated in a helium stream to 1000 C provides information on mineral types and their associations. The isotopic composition of O, H, C, and S can be precisely determined in several evolved compounds and compared with the present day atmosphere. Such SAM results might be able to test mineralogical evidence of changing sedimentary and alteration processes over an extended period of time. For example, Bibring et al (2006) have suggested such a major shift from early nonacidic to later acidic alteration. We will illustrate through a variety of evolved gas experiments implemented under SAM-like gas flow and temperature ramp conditions on terrestrial analog minerals on high fidelity Sam breadboards the type of chemical information we expect SAM to provide.

Mahaffy, Paul↗

NASA NTRS2014

Elemental Geochemistry of Sedimentary Rocks at Yellowknife Bay, Gale Crater, Mars

Sedimentary rocks examined by the Curiosity rover at Yellowknife Bay, Mars, were derived from sources that evolved from an approximately average martian crustal composition to one influenced by alkaline basalts. No evidence of chemical weathering is preserved, indicating arid, possibly cold, paleoclimates and rapid erosion and deposition. The absence of predicted geochemical variations indicates that magnetite and phyllosilicates formed by diagenesis under low-temperature, circumneutral pH, rock-dominated aqueous conditions. Analyses of diagenetic features (including concretions, raised ridges, and fractures) at high spatial resolution indicate that they are composed of iron- and halogen-rich components, magnesium-iron-chlorine-rich components, and hydrated calcium sulfates, respectively. Composition of a cross-cutting dike-like feature is consistent with sedimentary intrusion. The geochemistry of these sedimentary rocks provides further evidence for diverse depositional and diagenetic sedimentary environments during the early history of Mars.

Research Support, U.S. Gov't, Non-P.H.S.↗

NASA NTRS2016

STXM-XANES Analysis of Organic Matter in Dark Clasts and Halite Crystals in Zag and Monahans Meteorites

Zag and Monahans meteorites (H5) contains xenolithic dark clasts and halite (NaCl) crystals [e.g., 1]. The proposed source of the H chondrites is asteroid 6 Hebe [2]. The modern orbits of 1 Ceres and 6 Hebe essentially cross, with aphelion/perihelion of Ceres and Hebe of 2.99/2.55 and 2.91/1.94 AU (Astronomical Units), respectively. Therefore, Ceres might be the source of the clasts and halite in Zag and Monahans meteorites. Recent results from NASA's Dawn mission shows that bright spots in Ceres's crater may be hydrated magnesium sulfate with some water ice, and an average global surface contains ammoniated phyllosilicates that is likely of outer Solar System origin. One dark clast and all halite crystals in Zag and Monahans meteorites contain carbon-rich particles. We report organic analyses of these carbon-rich particles using carbon, nitrogen, and oxygen X-ray absorption near edge structure (C-, N-, and O-XANES), in order to constrain the origin of the clast and halite crystals.

Kebukawa, Y.↗

NASA NTRSDate not supplied

Characterizing the Effects of Thermal Profile and Gas Environment on the Heat Treatment of JSC-1A Lunar Simulant Using Combined Thermogravimetry and Mass Spectroscopy

As NASA strives towards a long duration presence on the Moon, it has become increasingly important to learn how to better utilize resources from the lunar surface for everything from habitats, vehicle infrastructure, and chemical extraction. To that end, a variety of lunar simulants have been sourced from terrestrially available volcanic minerals and glass as Apollo regolith is a finite resource unavailable for experimentation needing large masses. However, while mineralogy and chemical composition can approach that of lunar material in these simulants, there are still distinct non-lunar phases such as hydrates, carbonates, sulfates, and clays that can cause simulants to behave distinctly non-lunar in a variety of processing conditions that would ideally be applied to lunar material. Notably, severe glassy bubbling has been documented in a variety of vacuum sintering experiments on JSC-1A lunar Maria simulant heated via microwaves. The origins of this outgassing have not been well understood, but are normally attributed to the decomposition of non-lunar contaminates intrinsic to virtually all terrestrially sourced simulants. As such, a series of controlled environmental tests were performed to ascertain the origins of the high temperature outgassing and to develop heat treatments that can drive JSC-1A closer to lunar composition and behavior. It was found that in JSC-1A that distinct gas evolutions of water, carbon dioxide, and sulfur dioxide occur in both inert gas and vacuum. Additionally, the presence of hydrogen during heat treatments was shown to dramatically change gas evolutions, leading to distinctly more lunar-like composition and behavior from JSC-1A simulant.

sinter↗

NASA NTRSDate not supplied

Characterizing the Effects of Thermal Profile and Gas Environment on the Heat Treatment of JSC-1A Lunar Simulant Using Combined Thermogravimetry and Mass Spectroscopy

sinter↗

NASA NTRSDate not supplied

Mars Science Laboratory Mastcam Multispectral Investigation of Drill Targets From the Beginning of the Clay Sulfate Transition to Marker Band Valley

In March, 2021 the Mars Science Laboratory Curiosity rover officially started exploring the Clay Sulfate Transition (CST). This area of Mt. Sharp has been interpreted to have hydrated Mg-sulfate spectral signatures in CRISM orbital data, and it no longer has the strong phyllosilicate spectral signature as the previous Glen Torridon region. Recently, the Curiosity rover has also encountered the marker band that was also identified in orbital data [1,3]. This shift from phyllosilicates to hydrated Mg-sulfates suggests a major change in the environmental conditions during which these rocks were deposited. This abstract focuses on changes seen in the Mastcam multispectral data between the CST drill targets.

S R Jacob↗