Geology topics

S.M. Wiseman

Publications and source records attributed to S.M. Wiseman.

3 recordsLinked to original sources

USGS2009

A synthesis of Martian aqueous mineralogy after 1 Mars year of observations from the Mars Reconnaissance Orbiter

Martian aqueous mineral deposits have been examined and characterized using data acquired during Mars Reconnaissance Orbiter's (MRO) primary science phase, including Compact Reconnaissance Imaging Spectrometer for Mars hyperspectral images covering the 0.4-3.9 ??m wavelength range, coordinated with higher-spatial resolution HiRISE and Context Imager images. MRO's new high-resolution measurements, combined with earlier data from Thermal Emission Spectrometer; Thermal Emission Imaging System; and Observatoire pour la Min??ralogie, L'Eau, les Glaces et l'Activiti?? on Mars Express, indicate that aqueous minerals are both diverse and widespread on the Martian surface. The aqueous minerals occur in 9-10 classes of deposits characterized by distinct mineral assemblages, morphologies, and geologic settings. Phyllosilicates occur in several settings: in compositionally layered blankets hundreds of meters thick, superposed on eroded Noachian terrains; in lower layers of intracrater depositional fans; in layers with potential chlorides in sediments on intercrater plains; and as thousands of deep exposures in craters and escarpments. Carbonate-bearing rocks form a thin unit surrounding the Isidis basin. Hydrated silica occurs with hydrated sulfates in thin stratified deposits surrounding Valles Marineris. Hydrated sulfates also occur together with crystalline ferric minerals in thick, layered deposits in Terra Meridiani and in Valles Marineris and together with kaolinite in deposits that partially infill some highland craters. In this paper we describe each of the classes of deposits, review hypotheses for their origins, identify new questions posed by existing measurements, and consider their implications for ancient habitable environments. On the basis of current data, two to five classes of Noachian-aged deposits containing phyllosilicates and carbonates may have formed in aqueous environments with pH and water activities suitable for life. Copyright 2009 by the American Geophysical Union.

Journal of Geophysical Research E: Planets↗

USGS2008

Phyllosilicate and sulfate-hematite deposits within Miyamoto crater in Southern Sinus Meridiani, Mars

Orbital topographic, image, and spectral data show that sulfate- and hematite-bearing plains deposits similar to those explored by the MER rover Opportunity unconformably overlie the northeastern portion of the 160 km in diameter Miyamoto crater. Crater floor materials exhumed to the west of the contact exhibit CRISM and OMEGA NIR spectral signatures consistent with the presence of Fe/Mg-rich smectite phyllosilicates. Based on superposition relationships, the phyllosilicate-bearing deposits formed either in-situ or were deposited on the floor of Miyamoto crater prior to the formation of the sulfate-rich plains unit. These findings support the hypothesis that neutral pH aqueous conditions transitioned to a ground-water driven acid sulfate system in the Sinus Meridiani region. The presence of both phyllosilicate and sulfate- and hematite-bearing deposits within Miyamoto crater make it an attractive site for exploration by future rover missions. Copyright 2008 by the American Geophysical Union.

Geophysical Research Letters↗

USGS2006

Nature and origin of the hematite-bearing plains of Terra Meridiani based on analyses of orbital and Mars Exploration rover data sets

The ∼5 km of traverses and observations completed by the Opportunity rover from Endurance crater to the Fruitbasket outcrop show that the Meridiani plains consist of sulfate‐rich sedimentary rocks that are largely covered by poorly‐sorted basaltic aeolian sands and a lag of granule‐sized hematitic concretions. Orbital reflectance spectra obtained by Mars Express OMEGA over this region are dominated by pyroxene, plagioclase feldspar, crystalline hematite (i.e., concretions), and nano‐phase iron oxide dust signatures, consistent with Pancam and Mini‐TES observations. Mössbauer Spectrometer observations indicate more olivine than observed with the other instruments, consistent with preferential optical obscuration of olivine features in mixtures with pyroxene and dust. Orbital data covering bright plains located several kilometers to the south of the landing site expose a smaller areal abundance of hematite, more dust, and a larger areal extent of outcrop compared to plains proximal to the landing site. Low‐albedo, low‐thermal‐inertia, windswept plains located several hundred kilometers to the south of the landing site are predicted from OMEGA data to have more hematite and fine‐grained olivine grains exposed as compared to the landing site. Low calcium pyroxene dominates spectral signatures from the cratered highlands to the south of Opportunity. A regional‐scale model is presented for the formation of the plains explored by Opportunity, based on a rising ground water table late in the Noachian Era that trapped and altered local materials and aeolian basaltic sands. Cessation of this aqueous process led to dominance of aeolian processes and formation of the current configuration of the plains.

Journal of Geophysical Research E: Planets↗