To read the full-text of this research, you can request a copy directly from the authors.
Abstract
We apply an automated band detection algorithm, based on the wavelet transform, to the TES dataset. We find a band at 1120 cm^ 1, consistent, with sulfate-cemented soils, in the region already suspected to have a high sulfate concentration.
To read the full-text of this research, you can request a copy directly from the authors.
... Bandfield et al. (2003) report that carbonates are present in martian dust. Orbital data also indicate that sulfates are present in Mars soils, perhaps as soil cement (Gendrin and Mustard, 2004). Epsomite (Mg-sulfate; not shown here) is known to be present in the Dry Valleys, and as a terrestrial weathering product of Antarctic carbonaceous chondrites (Velbel, 1988). ...
... Mg-sulfate (species unknown) is also one of the definite martian salts in Nakhla (see Fig. 1), as characterized by Gooding et al. (1991). In fact, significant amounts of Mg-sulfates may be present at or near the surface of Mars (Gendrin and Mustard, 2004;Feldman et al., 2004). The Gooding et al. (1991) occurrence in Nakhla demonstrates that they are present at least in trace amounts. ...
The Dry Valleys of Antarctica are an excellent analog of the environment at the surface of Mars. Soil formation histories involving slow processes of sublimation and migration of water-soluble ions in polar desert environments are characteristic of both Mars and the Dry Valleys. At the present time, the environment in the Dry Valleys is probably the most similar to that in the mid-latitudes on Mars although similar conditions may be found in areas of the polar regions during their respective Mars summers. It is thought that Mars is currently in an interglacial period, and that subsurface water ice is sublimating poleward. Because the Mars sublimation zones seem to be the most similar to the Antarctic Dry Valleys, the Dry Valleys-type Mars climate is migrating towards the poles. Mars has likely undergone drastic obliquity changes, which means that the Dry Valleys analog to Mars may be valid for large parts of Mars, including the polar regions, at different times in geologic history. Dry Valleys soils contain traces of silicate alteration products and secondary salts much like those found in Mars meteorites. A martian origin for some of the meteorite secondary phases has been verified previously; it can be based on the presence of shock effects and other features which could not have formed after the rocks were ejected from Mars, or demonstrable modification of a feature by the passage of the meteorite through Earth's atmosphere (proving the feature to be pre-terrestrial). The martian weathering products provide critical information for deciphering the near-surface history of Mars. Definite martian secondary phases include Ca-carbonate, Ca-sulfate, and Mg-sulfate. These salts are also found in soils from the Dry Valleys of Antarctica. Results of earlier Wright Valley work are consistent with what is now known about Mars based on meteorite and orbital data. Results from recent and current Mars missions support this inference. Aqueous processes are active even in permanently frozen Antarctic Dry Valleys soils, and similar processes are probably also occurring on Mars today, especially at the mid-latitudes. Both weathering products and life in Dry Valleys soils are distributed heterogeneously. Such variations should be taken into account in future studies of martian soils and also in the search for possible life on Mars.
... This peak suggests that either the sulfate abundances are elevated as an artifact of the deconvolution algorithm (e.g., Bandfield, 2002), or that a minor sulfate component may indeed be present but not enough to be confidently detected. Consistent with this finding, previous work with TES data also suggested a tentative widespread occurrence of sulfates with abundances < 8% on Mars surface units (Cooper and Mustard, 2001;Gendrin and Mustard, 2004), and as a minor component of some southern hemisphere dune fields (e.g., Charles et al., 2017). ...
... Other Earth-based telescopic spectra of Mars suggest the presence of low symmetry sulfates or bisulfates, on the basis of absorption features located near 8.7 µm (1150 cm −1 ) and 9.8 µm (1020 cm −1 ) (Pollack et al., 1990). An absorption feature near 8.93 µm (1120 cm −1 ) in Mars Global Surveyor TES data is correlated with areas of high sulfur abundance (Gendrin and Mustard, 2004). Bandfield (2002) tentatively identified a few areas in Acidalia that may contain sulfate minerals (type unknown but probably a Ca-sulfate) just above the detection limit (∼10%) using TES data. ...
A suite of sulfate minerals were characterized spectrally, compositionally, and structurally in order to develop spectral reflectance–compositional–structural relations for this group of minerals. Sulfates exhibit diverse spectral properties, and absorption-band assignments have been developed for the 0.3–26 μm range. Sulfate absorption features can be related to the presence of transition elements, OH, H2O, and SO4 groups. The number, wavelength position, and intensity of these bands are a function of both composition and structure. Cation substitutions can affect the wavelength positions of all major absorption bands. Hydroxo-bridged Fe3+ results in absorption bands in the 0.43, 0.5, and 0.9 μm regions, while the presence of Fe2+ results in absorption features in the 0.9–1.2 μm interval. Fundamental SO bending and stretching vibration absorption bands occur in the 8–10, 13–18, and 19–24 μm regions (1000–1250, 550–770, and 420–530 cm−1). The most intense combinations and overtones of these fundamentals are found in the 4–5 μm (2000–2500 cm−1) region. Absorption features seen in the 1.7–1.85 μm interval are attributable to HOH/OH bending and translation/rotation combinations, while bands in the 2.1–2.7 μm regions can be attributed to H2O- and OH-combinations as well as overtones of SO bending fundamentals. OH- and H2O-bearing sulfate spectra are fundamentally different from each other at wavelengths below ∼6 μm. Changes in H2O/OH content can shift SO band positions due to change in bond lengths and structural rearrangement. Differences in absorption band wavelength positions enable discrimination of all the sulfate minerals used in this study in a number of wavelength intervals. Of the major absorption band regions, the 4–5 μm region seems best for identifying and discriminating sulfates in the presence of other major rock-forming minerals.
... Other Earth-based telescopic spectra of Mars suggest the presence of low symmetry sulfates or bisulfates, on the basis of absorption features located near 8.7 µm (1150 cm −1 ) and 9.8 µm (1020 cm −1 ) (Pollack et al., 1990). An absorption feature near 8.93 µm (1120 cm −1 ) in Mars Global Surveyor TES data is correlated with areas of high sulfur abundance (Gendrin and Mustard, 2004). Bandfield (2002) tentatively identified a few areas in Acidalia that may contain sulfate minerals (type unknown but probably a Ca-sulfate) just above the detection limit (∼10%) using TES data. ...
Sulfate minerals have been identified in Martian meteorites and on Mars using a suite of instruments aboard the MER rovers. These results have confirmed previous groundbased observations and orbital measurements that suggested their presence. The orbiting OMEGA instrument on Mars Express is also finding evidence for sulfate. In order to better interpret remote-sensing data, we present here the results of a coordinated visible/near infrared (VNIR) reflectance, Moussbauer (MB), and thermal emittance study of wellcharacterized hydrous sulfate minerals.
For the first time, direct infrared spectral analyses of glasses with Martian compositions, altered under controlled conditions, are presented in order to assess surface weathering and regolith development on Mars. Basaltic glasses of Irvine and Backstay composition were synthesized and altered using H2SO4-HCl acid solutions (pH0-4). SEM/EDS, XRD, Raman, and infrared spectral measurements were acquired for each reaction product. Infrared spectra were also acquired from previously synthesized and altered glasses with Pathfinder measured compositions. Acid alteration on particles in the most acidic solutions (pH ≤ 1) yielded sulfate-dominated VNIR and TIR spectra with some silica influence. Spectral differences between alteration products from each starting material were present, reflecting strong sensitivity to changes in mineral assemblage. In the TIR, alteration features were preserved after reworking and consolidation. In the VNIR, hydrated sulfate features were present along with strong negative spectral slopes. Although such signatures are found in a few isolated locations on Mars with high resolution spectrometers, much of the Martian surface lacks these characteristics, suggesting that either: acid alteration occurred at pH ≥ 2, small amounts of sulfates were reworked with unaltered material, there is a prevalence of intermediate-to-high silica glass in Martian starting materials (more resistant to acid alteration), primary or added sulfur were lacking, alteration features are obscured by dust, and/or large scale, pervasive, acid-sulfate weathering of the Martian surface did not occur. These results highlight the need to better understand the spectral properties of altered Martian surface material in order to enhance the interpretation of remote spectra for altered terrains.
Recent reports of ∼30wt% of sulphate within saline sediments on Mars1,2 - probably occurring in hydrated form3 - suggest a role for sulphates in accounting for equatorial H2O observed in a global survey by the Odyssey spacecraft4. Among salt hydrates likely to be present3, those of the MgSO4·nH2O series have many hydration states. Here we report the exposure of several of these phases to varied temperature, pressure and humidity to constrain their possible H2O contents under martian surface conditions. We found that crystalline structure and H2O content are dependent on temperature-pressure history, that an amorphous hydrated phase with slow dehydration kinetics forms at <1% relative humidity, and that equilibrium calculations may not reflect the true H2O-bearing potential of martian soils. Mg sulphate salts can retain sufficient H2O to explain a portion of the Odyssey observations5. Because phases in the MgSO4·nH2O system are sensitive to temperature and humidity, they can reveal much about the history of water on Mars. However, their ease of transformation implies that salt hydrates collected on Mars will not be returned to Earth unmodified, and that accurate in situ analysis is imperative.
Chemical analyses of soil samples performed at different landing sites on Mars suggest the presence of sulfate minerals. These minerals are also thought to be present in the globally mixed Martian bright soils covering large areas of the planet. However, remote soil spectra have so far provided only tentative identification of sulfates regarding mineral types and abundances. This paper concentrates on the detectability of four Ca- and Mg-sulfates (anhydrite, gypsum, kieserite, hexahydrite) in the 4–5 μm range of Martian remote soil spectra. This spectral range is important for sulfate detection as most fine-grained sulfates exhibit significant absorption bands between 4 and 5 μm, independent of the texture of the host soils (e.g., loose powdered or cemented soils). Furthermore, this is the spectral range for which the Planetary Fourier Spectrometer (PFS) and Observatoire pour la Minéralogie, l’Eau, les Glaces, et l’Activité (OMEGA) instruments onboard ESA/Mars Express mission provide high spectral and spatial resolution data. Laboratory near- and mid-IR reflectance spectra of the pure sulfates and their mixtures with a terrestrial Martian soil analog were acquired. The results show that even the smallest amount of admixed sulfate (∼5 wt%) generates significant absorption features in the portion of the 4–5 μm range not covered by the saturated Martian atmospheric CO2 absorption band between 4.2 and 4.4 μm. Model calculations of the influence of emitted surface radiation on the detectability of sulfate features show that the depth of the features decreases strongly with increasing surface temperature of an observed area resulting in the fact that all sulfates are spectrally hidden at surface temperatures around 270 K even at ∼14 or ∼25 wt% sulfate content in the soils. Sulfates become increasingly detectable depending on the sulfate content if the surface temperature is below 260 K. The outcome of this work helps to constrain the conditions needed for remote detection of sulfates within Martian bright soils in the 4–5 μm range.
The alpha proton x-ray spectrometer (APXS) on board the rover of the Mars Pathfinder mission measured the chemical composition
of six soils and five rocks at the Ares Vallis landing site. The soil analyses show similarity to those determined by the
Viking missions. The analyzed rocks were partially covered by dust but otherwise compositionally similar to each other. They
are unexpectedly high in silica and potassium, but low in magnesium compared to martian soils and martian meteorites. The
analyzed rocks are similar in composition to terrestrial andesites and close to the mean composition of Earth's crust. Addition
of a mafic component and reaction products of volcanic gases to the local rock material is necessary to explain the soil composition.
A method to analyze imaging spectrometry data is presented. It permits
automated detection and characterization of spectral features in large
data sets. Its capabilities are assessed on an AVIRIS image cube
acquired over the Hawaii volcanoes.
A global set of TES spectra was deconvolved using endmembers including a laboratory cemented sulfate soil. Good matches are found to the cemented sulfate and appear to represent detection of spatially-coherent regions of cemented sulfates on Mars.
Trends in element compositional variation among samples at the Viking lander sites on Mars provide evidence for multiple geochemical components in the soils. A simple two-component model can explain all pair-wise trends of eight elements analyzed. Component A contains Si and most or all the Al, Ca, Ti, and Fe. Component B, which is 16 +/- 3 percent by weight of the total, contains S and most or all the Cl and Mg. These results constrain several models of Martian soil mineralogy but are consistent with a mixture of silicates and salts.
ISM 3 µm water band strengths are compared to TES spectral features that fit cemented sulfate soils. Sulfate endmember exists only with high water abundances, strengthening the argument for sulfate detection.
Thermal Emission Spectrometer (TES) data from the Mars Global Surveyor (MGS) are used to determine compositions and distributions
of martian low-albedo regions. Two surface spectral signatures are identified from low-albedo regions. Comparisons with spectra
of terrestrial rock samples and deconvolution results indicate that the two compositions are a basaltic composition dominated
by plagioclase feldspar and clinopyroxene and an andesitic composition dominated by plagioclase feldspar and volcanic glass.
The distribution of the two compositions is split roughly along the planetary dichotomy. The basaltic composition is confined
to older surfaces, and the more silicic composition is concentrated in the younger northern plains.