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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Physical and chemical weathering

Physical and chemical weathering processes that might be important on Mars are reviewed, and the limited observations, including relevant Viking results and laboratory simulations, are summarized. Physical weathering may have included rock splitting through growth of ice, salt or secondary silicate crystals in voids. Chemical weathering probably involved reactions of minerals with water, oxygen, and carbon dioxide, although predicted products vary sensitively with the abundance and physical form postulated for the water. On the basis of kinetics data for hydration of rock glass on earth, the fate of weathering-rind formation on glass-bearing Martian volcanic rocks is tentatively estimated to have been on the order of 0.1 to 4.5 cm/Gyr; lower rates would be expected for crystalline rocks.

Gooding, James L.↗
NASA NTRS2004

Lunar and Planetary Science XXXV: Martian Meteorites: Chemical Weathering

The session "Martian Meteorites: Chemical Weathering" included the following reports:Chemical Weathering Records of Martian Soils Preserved in the Martian Meteorite EET79001; Synchrotron X-Ray Diffraction Analysis of Meteorites in Thin Section: Preliminary Results; A Survey of Olivine Alteration Products Using Raman Spectroscopy; and Rb-Sr and Sm-Nd Isotope Systematics of Shergottite NWA 856: Crystallization Age and Implications for Alteration of Hot Desert SNC Meteorites.

Source record↗
NASA NTRS2015

Silica Retention and Enrichment in Open-System Chemical Weathering on Mars

Chemical signatures of weathering are evident in the Alpha Particle X-ray Spectrometer (APXS) datasets from Gusev Crater, Meridiani Planum, and Gale Crater. Comparisons across the landing sites show consistent patterns indicating silica retention and/or enrichment in open-system aqueous alteration.

Yen, A. S.↗
NASA NTRS1985

Chemical Weathering of Soils from the Dry Valleys of Antarctica: a Terrestrial Analog of Martian Weathering Processes

Martian soil subjected to chemical weathering processes could contain the following likely constituents: (1) fresh primary silicate material; (2) partially altered primary silicates; (3) secondary minerals, possibly including clay minerals, evaporites, carbonates, sulfates, hydrates, and zeolites; and (4) altered volcanic glass or impact glass. The soil may also include palogonite and other alteration products and secondary minerals. It is unlikely therefore that an equilibrium assemblage of minerals would be present. From the detailed study of the soils from the Dry Valleys of Antarctica, it is obvious that the complex processes in operation produce major changes in the parent materials, depending upon where the constituents reside and the degree to which weathering and diagenesis operates. It is clear that natural near surface environments, even in very cold and dry regions, may produce extremely complex soils. Extreme caution must be taken when interpreting the results and drawing conclusions, especially about possible processes operating in regoliths in cold, arid environments similar to those of the Dry Valleys or Mars.

Gibson, E. K., Jr.↗
NASA NTRS2010

Allophane on Mars: Significance for Chemical Weathering and Soil Development

It has been suggested that allophane or related poorly crystalline aluminosilicates are present on Mars, and that they comprise the high-silica phase detected by the Thermal Emission Spectrometer (TES) in Surface Type 2 materials (Michalski et al., 2005). Using new laboratory spectra of allophanic materials, we (Rampe et al., this meeting) have detected allophane on the Martian surface via spectral modeling of TES data. We find that ST2 materials in the Northern Plains are consistent with a significant amount of high-silica allophane-like materials. In addition, we find that allophane may be present in some areas of ancient highlands (TES surface type 1), but spectra of those regions are more consistent with aluminous allophane. The presence of allophane and its chemical variability have important implications for chemical weathering and soil development on Mars. Allophane-like materials are amorphous or poorly crystalline hydrous aluminosilicates formed from chemical weathering of glasses, feldspars, and other silicates (cf. Parfitt, 2009). True allophane is a combination of SiO2, Al2O3 and H2O where Al:Si ranges from ~0.5-2. Aluminosilicate gels are amorphous and chemically similar to allophane but can have higher SiO2 contents. The presence of allophane indicates low-temperature chemical weathering and provides constraints on alteration conditions, limiting pH to circum-neutral (~4.5-8). Our model results indicate that weathering occurred in the relatively young northern plains of Mars. The high-silica allophane-like material present there implies little silica mobility through the soil column, which suggests that weathering involved small amounts of liquid water, consistent with our previous models of weathering in ice-rich soils (Kraft et al., 2007). The aluminous allophane indicated by our spectral models to be present in the highlands suggest that those regions experienced greater amounts of SiO2 leaching and weathering in those soils may have involved much larger amounts of water. The presence of allophane-like materials suggests that these weathering regimes were not influenced by the acidic weathering that appears to have affected other areas of Mars and has been proposed as a planetwide alteration process (Hurowitz and McLennan, 2007). Soil development in basaltic material (typically tephra) on Earth usually leads to formation of andosols. Although we do not suggest a one-to-one analogy between dark basaltic Martian soils and andosols, there may be important similarities, as andosols are typified by significant production of allophane as well as poorly crystalline Fe-hydroxides. The detection of allophane on Mars suggests a positive utility of an andosol model for Martian soils, particularly when coupled with the ubiquitous presence of Feoxide materials on Mars. An andosol model of soil formation is mineralogically consistent with palagonite models for the formation of Martian dust (cf. Banin et al., 1992; Morris et al., 2001), which suggests a possible genetic relationship of dust and bright soils to the broader soil layer of Mars.

Kraft, M. D.↗
NASA NTRS1992

MSATT Workshop on Chemical Weathering on Mars

The topics covered with respect to chemical weathering on Mars include the following: Mars soil, mineralogy, spectroscopic analysis, clays, silicates, oxidation, iron oxides, water, chemical reactions, geochemistry, minerals, Mars atmosphere, atmospheric chemistry, salts, planetary evolution, volcanology, Mars volcanoes, regolith, surface reactions, Mars soil analogs, carbonates, meteorites, and reactivity.

Burns, Roger↗
NASA NTRS1983

Chemical weathering and diagenesis of a cold desert soil from Wright Valley, Antarctica - An analog of Martian weathering processes

Weathering, diagenesis, and chemical alteration of a soil profile from the Dry Valleys of Antarctica are investigated as an analog to soil development within the Martian regolith. Soil samples from a soil pit one meter deep on Prospect Mesa, Wright Valley, are examined for their major element concentrations, water-soluble cations and anions, carbon, sulfur, and water concentrations, and related petrographic characteristics of weathering in a cold, dry environment. A petrographic study of the samples suggests that most silicate mineral and lithic fragments exhibit some degree of alteration. Chemical alteration occurs both in samples above and within the permanently frozen zone. The concentrations of water-soluble cations, for example, Na(+), K(+), Ca(2+), and anions, Cl(-), SO4(2-), NO3(-), are found to decrease significantly from the surface to the permanently frozen zone, suggesting a major movement of water-soluble species. It is also found that enrichments in secondary mineral abundances correlate with the water soluble ion concentrations. The formation of zeolites is seen throughout the soil column; these, it is thought, may be reservoirs for volatile storage within the regolith.

Gibson, E. K.↗
NASA NTRS1978

Chemical weathering on Mars - Thermodynamic stabilities of primary minerals /and their alteration products/ from mafic igneous rocks

Chemical weathering on Mars is examined theoretically from the standpoint of thermodynamic equilibrium between primary rock-forming minerals and the atmospheric gases O2, H2O, and CO2. The primary minerals considered are those common to mafic igneous rocks and include olivine, pyroxene, plagioclase, magnetite, troilite, pyrrhotite, and apatite. The importance of kinetics and reaction mechanisms in controlling possible weathering processes on Mars is discussed within the limits of currently available data, and the possible influence of liquid water on Martian weathering processes is evaluated where appropriate. For gas-solid weathering of mafic igneous rocks at the Martian surface, it is concluded that upon attainment of thermodynamic equilibrium: (1) oxides and carbonates should dominate the mineral assemblage of weathering products; (2) hematite rather than goethite should be the stable mineral form of Fe (III); (3) FeSO4 or FeSO4.H2O could be the stable weathering product of iron sulfides in the absence of liquid water; and (4) kaolinite is apparently the only clay mineral that should be thermodynamically stable over all ranges of temperature and water-vapor abundance at the Martian surface.

Gooding, J. L.↗
NASA NTRS2009

The Duration of Chemical Weathering of Gusev Crater's Wishstone-Watchtower Sequence

Mineralogical abundance of primary minerals versus secondary minerals, chemical mixing relationships, and elemental ratios have been used to assess the degree of aqueous alteration at Gusev Crater and Meridiani Planum. However, limited work has used Ti-normalized mass-balance analysis chemical data to quantify gains and losses of elements from altered materials as well as estimate the duration of aqueous alteration on Mars. The Ti-normalized mass-balance approach accounts for volumetric changes associated with geochemical alteration. If volumetric changes are not considered, observed geochemical trends based on un-normalized data have the potential to be misleading. Assessing gains and losses from altered materials can indicate the geochemistry of fluids involved in the alteration. Furthermore, elemental losses can be combined with dissolution rates to estimate the duration of chemical weathering. Knowledge of the duration of aqueous alteration will provide insight into the climate history of Mars as well as indicate the potential for microbial habitability. The Wishstone-Watchtower materials in Gusev Crater are suitable candidates for Ti-normalized mass-balance analysis because mixing relationships of these two materials indicate that Watchtower materials may be derived from Wishstone-like materials. The objectives of this work are to (1) employ Ti-normalized mass-balance to assess gains and losses from the Wishstone-Watchtower sequence and (2) to combine losses with laboratory dissolution rates to estimate alteration times of the Watchtower material.

Sutter, Brad↗
NASA NTRS1993

The rate of chemical weathering of pyrite on the surface of Venus

This abstract reports results of an experimental study of the chemical weathering of pyrite (FeS2) under Venus-like conditions. This work, which extends the earlier study by Fegley and Treiman, is part of a long range research program to experimentally measure the rates of thermochemical gas-solid reactions important in the atmospheric-lithospheric sulfur cycle on Venus. The objectives of this research are (1) to measure the kinetics of thermochemical gas-solid reactions responsible for both the production (e.g., anhydrite formation) and destruction (e.g., pyrrhotite oxidation) of sulfur-bearing minerals on the surface of Venus and (2) to incorporate these and other constraints into holistic models of the chemical interactions between the atmosphere and surface of Venus. Experiments were done with single crystal cubes of natural pyrite (Navajun, Logrono, Spain) that were cut and polished into slices of known weight and surface area. The slices were isothermally heated at atmospheric pressure in 99.99 percent CO2 (Coleman Instrument Grade) at either 412 C (685 K) or 465 C (738 K) for time periods up to 10 days. These two isotherms correspond to temperatures at about 6 km and 0 km altitude, respectively, on Venus. The reaction rate was determined by measuring the weight loss of the reacted slices after removal from the furnace. The reaction products were characterized by X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy on the SEM.

Fegley, B., Jr.↗
NASA NTRS1997

Chemical Weathering Kinetics of Basalt on Venus

The purpose of this project was to experimentally measure the kinetics for chemical weathering reactions involving basalt on Venus. The thermochemical reactions being studied are important for the CO2 atmosphere-lithosphere cycle on Venus and for the atmosphere-surface reactions controlling the oxidation state of the surface of Venus. These reactions include the formation of carbonate and scapolite minerals, and the oxidation of Fe-bearing minerals. These experiments and calculations are important for interpreting results from the Pioneer Venus, Magellan, Galileo flyby, Venera, and Vega missions to Venus, for interpreting results from Earth-based telescopic observations, and for the design of new Discovery class (e.g., VESAT) and New Millennium missions to Venus such as geochemical landers making in situ elemental and mineralogical analyses, and orbiters, probes and balloons making spectroscopic observations of the sub-cloud atmosphere of Venus.

Fegley, Bruce, Jr.↗
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.↗
DOE OSTI2024

Hydrological control of chemical weathering and rock-carbon fluxes: East River, Colorado

This data package is used in the manuscript entitled “Hydrological control of chemical weathering and rock-carbon fluxes”. The field study was conducted in a lower montane hillslope of the East River watershed, underlain by Mancos Shale, within the lower 140 m section of a transect that extends nearly 1 km to its local peak. The data in this package, in CSV file format, were collected from Fall 2016 to fall 2021, including depth-resolved dynamic water table depths, subsurface water fluxes, solid phase (soil to bedrock) chemical compositions, geochemical properties of porewater and pore-gas, including radio carbon concentrations. The detailed methods of field studies, laboratory chemical analyses, and calculations are described in the Methods section and in the dataset file: Wan_et_al_Methods.pdf. The dataset additionally includes a file-level metadata (flmd.csv) file that lists each file contained in the dataset with associated metadata; and a data dictionary (dd.csv) file that contains column/row headers used throughout the files along with a definition, units, and data type.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1992

Workshop on chemical weathering on Mars, part 2

The third Mars Surface and Atmosphere Through Time (MSATT) Workshop, which was held 10-12 Sep. 1992, at Cocoa Beach/Cape Kennedy, focused on chemical weathering of the surface of Mars. The 30 papers presented at the workshop described studies of Martian weathering processes based on results from the Viking mission experiments, remote sensing spectroscopic measurements, studies of the shergottite, nakhlite, and chassignite (SNC) meteorites, laboratory measurements of surface analog materials, and modeling of reaction pathways. A summary of the technical sessions is presented and a list of workshop participants is included.

Burns, Roger↗
NASA NTRS2004

Evidence for Differential Comminution/Aeolian Sorting and Chemical Weathering of Martian Soils Preserved in Mars Meteorite EET79001

Impact-melt glasses containing Martian atmospheric gases in Mars meteorite EET79001 are formed from Martian soil fines that had undergone meteoroid-comminution and aeolian sorting accompanied by chemical weathering near Mars surface. Using SiO2 and SO3 as proxy for silicates and salts respectively in Mars soils, we find that SiO2 and SO3 correlate negatively with FeO and MgO and positively with Al2O3 and CaO in these glasses, indicating that the mafic and felsic components are depleted and enriched relative to the bulk host (Lith A/B) respectively as in the case of Moon soils. Though the overall pattern of mineral fractionation is similar between the soil fines on Mars and Moon, the magnitudes of the enrichments/depletions differ between these sample-suites because of pervasive aeolian activity on Mars. In addition to this mechanical processing, the Martian soil fines, prior to impact-melting, have undergone acid-sulfate dissolution under oxidizing/reducing conditions. The S03 content in EET79001,507 (Lith B) glass is approx.18% compared to < 2% in EET79001, 506 (Lith A). SiO2 and SO3 negatively correlate with each other in ,507 glasses similar to Pathfinder soils. The positive correlation found between FeO and SO3 in ,507 glasses as well as Pathfinder rocks and soils is consistent with the deposition of ferric-hydroxysulfate on regolith grains in an oxidizing environment. As in the case of Pathfinder soils, the Al 2O3 vs SiO2 positive correlation and FeO VS S102 negative correlation observed in ,507 glasses indicate that SiO2 from the regolith is mobilized as soluble silicic acid at low pH. The large off-set in the end-member FeO abundance ( SO3=0) between Pathfinder soil-free rock and sulfur-free rock in ,507 glass precursors suggests that the soils comprising the ,507 glasses contain much larger proportion of fine-grained Martian soil fraction that registers strong mafic depletion relative to Lith B. This inference is strongly supported by the Al2O3 - SO3 negative correlation observed in both ,507 glasses and pathfinder soils. Furthermore, the flat MgO-SO3 correlation observed in the case of ,507 glasses shows that the solubilized MgSO4 is mobilized by the aqueous solutions leaving behind the rock-residue with approx.2-3% MgO. This value is similar to the approx.2% MgO found for the soil-free rock at the Pathfinder site. The EET79001 ,506 glasses, in contrast, show that Al2O3 and CaO positively correlate with SO3 indicating that Al is precipitated as amorphous hydroxysulfate at relatively high pH. The FeO - SO3 negative correlation observed in ,506 glasses yields an end-member FeO abundance of approx.21% for the sulfur-free rock, which is consistent with the 22% FeO deduced for the Viking soil-free rock. Further, the FeO and MgO negative correlation with S03 observed in ,506 glasses indicates that the divalent Fe and Mg released from ferromagnesian minerals by acid sulfate dissolution are mobilized away from the reaction sites as soluble sulfates under reducing environment. A similar negative correlation between FeO and SO3 and a positive correlation between Al2O3 and SO3 found in Viking soils suggest that they also had undergone acid-sulfate dissolution under relatively reducing conditions.

Rao, M. N.↗
NASA NTRS1993

Chemical weathering on Mars: Rate of oxidation of iron dissolved in brines

Salts believed to occur in Martian regolith imply that brines occur on Mars, which may have facilitated the oxidation of dissolved Fe(2+) ions after they were released during chemical weathering of basaltic ferromagnesian silicate and iron sulfide minerals. Calculations show that the rate of oxidation of Fe(2+) ions at -35 C in a 6M chloride-sulfate brine that might exist on Mars is about 10(exp 6) times slower that the oxidation rate of iron in ice-cold terrestrial seawater.

Burns, Roger G.↗
NASA NTRSDate not supplied

Investigating Physical and Chemical Weathering of Fluvial and Aeolian Sediments in Mars-Analog Environments Using Close-Up Image Analysis

Results from the NASA Curiosity rover show that the ancient (>3 Ga) sedimentary rocks in Gale crater formed by fluvial and lacustrine processes, with aeolian processes dominating the geological record after the river-lake system ended in the Hesperian. The sedimentary system in Gale crater contains a mineralogy dominated by basaltic materials, not the quartzofeldspathic minerals that derive most sedimentary rocks on the Earth. There remains a knowledge gap for understanding how basaltic materials are physically and chemically weathered in fluvial and aeolian environments. This research aims to under-stand how the physical and chemical characteristics of basaltic sediments change as they are transported from source-to-sink in Mars-analog environments utilizing close-up images and X-Ray Diffraction (XRD) analysis. These data were collected as part of the SAND-E mission.

F D Garcia Ledezma↗
NASA NTRS1982

Chemical weathering and the Viking biology experiments on Mars

Since the publication of studies describing models that do not require external energy sources, new LR (labeled release) test standards module studies have been reported by Levin and Straat (1981). These studies impose important constraints on the various models, and they offer strong support for the 'frost-weathering' model. These findings are discussed here, and it is proposed that the activity of all three biology experiments can now adequately be explained as a consequence of a single active agent produced by contemporary chemical weathering. Some of the possible consequences and implications of contemporary weathering for the current state and evolution of the regolith and atmosphere are briefly discussed.

Huguenin, R. L.↗