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  • 1
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    Mars Reconnaissance Orbiter and Opportunity Observations of the Burns Formation: Crater-Hopping at Meridiani Planum (2015)
    Wiley
    Details
    Publication Date: 2015-02-10
    Description: CRISM hyperspectral (1.0-2.65 µm) along-track oversampled observations (ATOs) covering Victoria, Santa Maria, Endeavour, and Ada craters were processed to 6 m/pixel and used in combination with Opportunity observations to detect and map hydrated Mg and Ca-sulfate minerals in the Burns formation. The strongest spectral absorption features were found to be associated with outcrops that are relatively young and fresh (Ada) or preferentially scoured of dust, soil, and coatings by prevailing winds. At Victoria and Santa Maria the scoured areas are on the southeastern rims and walls, opposite to the sides where wind-blown sands extend out of the craters. At Endeavour the deepest absorptions are in Botany Bay, a subdued and buried rim segment that exhibits high thermal inertias, extensive outcrops, and is interpreted to be a region of enhanced wind scour extending up and out of the crater. Ada, Victoria, and Santa Maria outcrops expose the upper portion of the preserved Burns formation and show spectral evidence for the presence of kieserite. In contrast, gypsum is pervasive spectrally in the Botany Bay exposures. Gypsum, a relatively insoluble evaporative mineral, is interpreted to have formed close to the contact with the Noachian crust as rising ground waters brought brines close to and onto the surface, either as a direct precipitate or during later diagenesis. The presence of kieserite at the top of the section is hypothesized to reflect precipitation from evaporatively concentrated brines or dehydration of polyhydrated sulfates, in both scenarios as the aqueous environment evolved to very arid conditions.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    Context of ancient aqueous environments on Mars from in situ geologic mapping at Endeavour crater (2015)
    Wiley
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    Publication Date: 2015-02-12
    Description: Using the Mars Exploration Rover Opportunity , we have compiled one of the first field geologic maps on Mars while traversing the Noachian terrain along the rim of the 22-km diameter Endeavour crater (Lat -2° 16’ 33”, Long -5° 10’ 51”). In situ mapping of the petrographic, elemental, structural, and stratigraphic characteristics of outcrops and rocks distinguishes four mappable bedrock lithologic units. Three of these rock units pre-date the surrounding Burns formation sulfate-rich sandstones and one, the Matijevic formation, represents conditions on early Mars pre-dating the formation of Endeavour crater. The stratigraphy assembled from these observations includes several geologic unconformities. The differences in lithologic units across these unconformities record changes in the character and intensity of the Martian aqueous environment over geologic time. Water circulated through fractures in the oldest rocks over periods long enough that texturally and elementally significant alteration occurred in fracture walls. These oldest pre-Endeavour rocks and their network of mineralized and altered fractures were preserved by burial beneath impact ejecta and were subsequently exhumed and exposed. The alteration along joints in the oldest rocks, and the mineralized veins and concentrations of trace metals in overlying lithologic units is direct evidence that copious volumes of mineralized and/or hydrothermal fluids circulated through the early Martian crust. The wide range in intensity of structural and chemical modification from outcrop to outcrop along the crater rim shows that the ejecta of large (〉8 km in diameter) impact craters is complex. These results imply that geologic complexity is to be anticipated in other areas of Mars where cratering has been a fundamental process in the local and regional geology and mineralogy.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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  • 3
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    Temporal observations of bright soil exposures at Gusev crater, Mars (2011)
    Wiley
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    Publication Date: 2011-01-27
    Description: The Mars Exploration Rover Spirit has discovered bright soil deposits in its wheel tracks that previously have been confirmed to contain ferric sulfates and/or opaline silica. Repeated Pancam multispectral observations have been acquired at four of these deposits to monitor spectral and textural changes over time during exposure to Martian surface conditions. Previous studies suggested that temporal spectral changes occur because of mineralogic changes (e.g., phase transitions accompanying dehydration). In this study, we present a multispectral and temporal analysis of eight Pancam image sequences at the Tyrone exposure, three at the Gertrude Weise exposure, two at the Kit Carson exposure, and ten at the Ulysses exposure that have been acquired as of sol 2132 (1 January 2010). We compare observed variations in Pancam data to spectral changes predicted by laboratory experiments for the dehydration of ferric sulfates. We also present a spectral analysis of repeated Mars Reconnaissance Orbiter HiRISE observations spanning 32 sols and a textural analysis of Spirit Microscopic Imager observations of Ulysses spanning 102 sols. At all bright soil exposures, we observe no statistically significant spectral changes with time that are uniquely diagnostic of dehydration and/or mineralogic phase changes. However, at Kit Carson and Ulysses, we observe significant textural changes, including slumping within the wheel trench, movement of individual grains, disappearance of fines, and dispersal of soil clods. All observed textural changes are consistent with aeolian sorting and/or minor amounts of air fall dust deposition.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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  • 4
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    Opportunity Mars Rover mission: Overview and selected results from Purgatory ripple to traverses to Endeavour crater (2011)
    Wiley
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    Publication Date: 2011-02-08
    Description: Opportunity has been traversing the Meridiani plains since 25 January 2004 (sol 1), acquiring numerous observations of the atmosphere, soils, and rocks. This paper provides an overview of key discoveries between sols 511 and 2300, complementing earlier papers covering results from the initial phases of the mission. Key new results include (1) atmospheric argon measurements that demonstrate the importance of atmospheric transport to and from the winter carbon dioxide polar ice caps; (2) observations showing that aeolian ripples covering the plains were generated by easterly winds during an epoch with enhanced Hadley cell circulation; (3) the discovery and characterization of cobbles and boulders that include iron and stony-iron meteorites and Martian impact ejecta; (4) measurements of wall rock strata within Erebus and Victoria craters that provide compelling evidence of formation by aeolian sand deposition, with local reworking within ephemeral lakes; (5) determination that the stratigraphy exposed in the walls of Victoria and Endurance craters show an enrichment of chlorine and depletion of magnesium and sulfur with increasing depth. This result implies that regional-scale aqueous alteration took place before formation of these craters. Most recently, Opportunity has been traversing toward the ancient Endeavour crater. Orbital data show that clay minerals are exposed on its rim. Hydrated sulfate minerals are exposed in plains rocks adjacent to the rim, unlike the surfaces of plains outcrops observed thus far by Opportunity. With continued mechanical health, Opportunity will reach terrains on and around Endeavour's rim that will be markedly different from anything examined to date.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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  • 5
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    Evidence for mechanical and chemical alteration of iron-nickel meteorites on Mars: Process insights for Meridiani Planum (2011)
    Wiley
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    Publication Date: 2011-04-19
    Description: The weathering of meteorites found on Mars involves chemical and physical processes that can provide clues to climate conditions at the location of their discovery. Beginning on sol 1961, the Opportunity rover encountered three large iron meteorites within a few hundred meters of each other. In order of discovery, these rocks have been assigned the unofficial names Block Island, Shelter Island, and Mackinac Island. Each rock presents a unique but complimentary set of features that increase our understanding of weathering processes at Meridiani Planum. Significant morphologic characteristics interpretable as weathering features include (1) a large pit in Block Island, lined with delicate iron protrusions suggestive of inclusion removal by corrosive interaction; (2) differentially eroded kamacite and taenite lamellae in Block Island and Shelter Island, providing relative timing through crosscutting relationships with deposition of (3) an iron oxide–rich dark coating; (4) regmaglypted surfaces testifying to regions of minimal surface modification, with other regions in the same meteorites exhibiting (5) large-scale, cavernous weathering (in Shelter Island and Mackinac Island). We conclude that the current size of the rocks is approximate to their original postfall contours. Their morphology thus likely results from a combination of atmospheric interaction and postfall weathering effects. Among our specific findings is evidence supporting (1) at least one possible episode of aqueous acidic exposure for Block Island; (2) ripple migration over portions of the meteorites; (3) a minimum of two separate episodes of wind abrasion; alternating with (4) at least one episode of coating-forming chemical alteration, most likely at subzero temperatures.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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  • 6
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    Field reconnaissance geologic mapping of the Columbia Hills, Mars, based on Mars Exploration Rover Spirit and MRO HiRISE observations (2011)
    Wiley
    Details
    Publication Date: 2011-07-07
    Description: Chemical, mineralogic, and lithologic ground truth was acquired for the first time on Mars in terrain units mapped using orbital Mars Reconnaissance Orbiter's High Resolution Imaging Science Experiment (MRO HiRISE) image data. Examination of several dozen outcrops shows that Mars is geologically complex at meter length scales, the record of its geologic history is well exposed, stratigraphic units may be identified and correlated across significant areas on the ground, and outcrops and geologic relationships between materials may be analyzed with techniques commonly employed in terrestrial field geology. Despite their burial during the course of Martian geologic time by widespread epiclastic materials, mobile fines, and fall deposits, the selective exhumation of deep and well-preserved geologic units has exposed undisturbed outcrops, stratigraphic sections, and structural information much as they are preserved and exposed on Earth. A rich geologic record awaits skilled future field investigators on Mars. The correlation of ground observations and orbital images enables construction of a corresponding geologic reconnaissance map. Most of the outcrops visited are interpreted to be pyroclastic, impactite, and epiclastic deposits overlying an unexposed substrate, probably related to a modified Gusev crater central peak. Fluids have altered chemistry and mineralogy of these protoliths in degrees that vary substantially within the same map unit. Examination of the rocks exposed above and below the major unconformity between the plains lavas and the Columbia Hills directly confirms the general conclusion from remote sensing in previous studies over past years that the early history of Mars was a time of more intense deposition and modification of the surface. Although the availability of fluids and the chemical and mineral activity declined from this early period, significant later volcanism and fluid convection enabled additional, if localized, chemical activity.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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  • 7
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    The construction of Chasma Boreale on Mars (2010)
    Nature Publishing Group (NPG)
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    Publication Date: 2010-05-28
    Description: The polar layered deposits of Mars contain the planet's largest known reservoir of water ice and the prospect of revealing a detailed Martian palaeoclimate record, but the mechanisms responsible for the formation of the dominant features of the north polar layered deposits (NPLD) are unclear, despite decades of debate. Stratigraphic analyses of the exposed portions of Chasma Boreale-a large canyon 500 km long, up to 100 km wide, and nearly 2 km deep-have led most researchers to favour an erosional process for its formation following initial NPLD accumulation. Candidate mechanisms include the catastrophic outburst of water, protracted basal melting, erosional undercutting, aeolian downcutting and a combination of these processes. Here we use new data from the Mars Reconnaissance Orbiter to show that Chasma Boreale is instead a long-lived, complex feature resulting primarily from non-uniform accumulation of the NPLD. The initial valley that later became Chasma Boreale was matched by a second, equally large valley that was completely filled in by subsequent deposition, leaving no evidence on the surface to indicate its former presence. We further demonstrate that topography existing before the NPLD began accumulating influenced successive episodes of deposition and erosion, resulting in most of the present-day topography. Long-term and large-scale patterns of mass balance achieved through sedimentary processes, rather than catastrophic events, ice flow or highly focused erosion, have produced the largest geomorphic anomaly in the north polar ice of Mars.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Holt, J W -- Fishbaugh, K E -- Byrne, S -- Christian, S -- Tanaka, K -- Russell, P S -- Herkenhoff, K E -- Safaeinili, A -- Putzig, N E -- Phillips, R J -- England -- Nature. 2010 May 27;465(7297):446-9. doi: 10.1038/nature09050.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, Austin 78758, Texas, USA. jack@ig.utexas.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20505721" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 8
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    Exploration of Victoria crater by the Mars rover Opportunity (2009)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 2009-05-23
    Description: The Mars rover Opportunity has explored Victoria crater, an approximately 750-meter eroded impact crater formed in sulfate-rich sedimentary rocks. Impact-related stratigraphy is preserved in the crater walls, and meteoritic debris is present near the crater rim. The size of hematite-rich concretions decreases up-section, documenting variation in the intensity of groundwater processes. Layering in the crater walls preserves evidence of ancient wind-blown dunes. Compositional variations with depth mimic those approximately 6 kilometers to the north and demonstrate that water-induced alteration at Meridiani Planum was regional in scope.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Squyres, S W -- Knoll, A H -- Arvidson, R E -- Ashley, J W -- Bell, J F 3rd -- Calvin, W M -- Christensen, P R -- Clark, B C -- Cohen, B A -- de Souza, P A Jr -- Edgar, L -- Farrand, W H -- Fleischer, I -- Gellert, R -- Golombek, M P -- Grant, J -- Grotzinger, J -- Hayes, A -- Herkenhoff, K E -- Johnson, J R -- Jolliff, B -- Klingelhofer, G -- Knudson, A -- Li, R -- McCoy, T J -- McLennan, S M -- Ming, D W -- Mittlefehldt, D W -- Morris, R V -- Rice, J W Jr -- Schroder, C -- Sullivan, R J -- Yen, A -- Yingst, R A -- New York, N.Y. -- Science. 2009 May 22;324(5930):1058-61. doi: 10.1126/science.1170355.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Astronomy, Space Sciences Building, Cornell University, Ithaca, NY 14853, USA. squyres@astro.cornell.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19461001" target="_blank"〉PubMed〈/a〉
    Keywords: Extraterrestrial Environment ; Ferric Compounds ; *Mars ; Spacecraft ; Water
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 9
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    Results from the Mars Pathfinder camera (1997)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1997
    Description: Images of the martian surface returned by the Imager for Mars Pathfinder (IMP) show a complex surface of ridges and troughs covered by rocks that have been transported and modified by fluvial, aeolian, and impact processes. Analysis of the spectral signatures in the scene (at 440- to 1000-nanometer wavelength) reveal three types of rock and four classes of soil. Upward-looking IMP images of the predawn sky show thin, bluish clouds that probably represent water ice forming on local atmospheric haze (opacity approximately 0.5). Haze particles are about 1 micrometer in radius and the water vapor column abundance is about 10 precipitable micrometers.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Smith, P H -- Bell, J F 3rd -- Bridges, N T -- Britt, D T -- Gaddis, L -- Greeley, R -- Keller, H U -- Herkenhoff, K E -- Jaumann, R -- Johnson, J R -- Kirk, R L -- Lemmon, M -- Maki, J N -- Malin, M C -- Murchie, S L -- Oberst, J -- Parker, T J -- Reid, R J -- Sablotny, R -- Soderblom, L A -- Stoker, C -- Sullivan, R -- Thomas, N -- Tomasko, M G -- Wegryn, E -- New York, N.Y. -- Science. 1997 Dec 5;278(5344):1758-65.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA. psmith@lpl.arizona.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9388170" target="_blank"〉PubMed〈/a〉
    Keywords: Atmosphere ; *Extraterrestrial Environment ; Ice ; *Mars ; Minerals ; *Water ; Wind
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 10
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    In situ evidence for an ancient aqueous environment at Meridiani Planum, Mars (2004)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2004-12-04
    Description: Sedimentary rocks at Eagle crater in Meridiani Planum are composed of fine-grained siliciclastic materials derived from weathering of basaltic rocks, sulfate minerals (including magnesium sulfate and jarosite) that constitute several tens of percent of the rock by weight, and hematite. Cross-stratification observed in rock outcrops indicates eolian and aqueous transport. Diagenetic features include hematite-rich concretions and crystal-mold vugs. We interpret the rocks to be a mixture of chemical and siliciclastic sediments with a complex diagenetic history. The environmental conditions that they record include episodic inundation by shallow surface water, evaporation, and desiccation. The geologic record at Meridiani Planum suggests that conditions were suitable for biological activity for a period of time in martian history.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Squyres, S W -- Grotzinger, J P -- Arvidson, R E -- Bell, J F 3rd -- Calvin, W -- Christensen, P R -- Clark, B C -- Crisp, J A -- Farrand, W H -- Herkenhoff, K E -- Johnson, J R -- Klingelhofer, G -- Knoll, A H -- McLennan, S M -- McSween, H Y Jr -- Morris, R V -- Rice, J W Jr -- Rieder, R -- Soderblom, L A -- New York, N.Y. -- Science. 2004 Dec 3;306(5702):1709-14.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Astronomy, Cornell University, Ithaca, NY 14853, USA. squyres@astrosun.tn.cornell.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/15576604" target="_blank"〉PubMed〈/a〉
    Keywords: Exobiology ; Extraterrestrial Environment ; Ferric Compounds ; Geologic Sediments ; Life ; *Mars ; Minerals ; Silicates ; Spacecraft ; Spectrum Analysis ; Sulfates ; Sulfur ; *Water
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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