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MER MB Publications
| Science, Vol.306, No. 5702, p. 1740 (2004)
Jarosite and Hematite at Meridiani Planum from Opportunity's Mössbauer Spectrometer
G. Klingelhöfer, R. V. Morris, B. Bernhardt, C. Schröder, D. S. Rodionov, P. A. de Souza, Jr., A. Yen, R. Gellert, E. N. Evlanov, B. Zubkov, J. Foh, U. Bonnes, E. Kankeleit, P. Gütlich, D. W. Ming, F. Renz, T. Wdowiak, S. W. Squyres, R. E. Arvidson
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Mössbauer spectra measured by the Opportunity rover revealed four mineralogical components in Meridiani Planum at Eagle crater: jarosite- and hematite-rich outcrop, hematite-rich soil, olivine-bearing basaltic soil, and a pyroxene-bearing basaltic rock (Bounce rock). Spherules, interpreted to be concretions, are hematite-rich and dispersed throughout the outcrop. Hematitic soils both within and outside Eagle crater are dominated by spherules and their fragments. Olivine-bearing basaltic soil is present throughout the region. Bounce rock is probably an impact erratic. Because jarosite is a hydroxide sulfate mineral, its presence at Meridiani Planum is mineralogical evidence for aqueous processes on Mars, probably under acid-sulfate conditions.
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| Science, Vol. 305, No. 5685, p.833 (2004)
Mineralogy at Gusev Crater from the Mössbauer Spectrometer on the Spirit Rover
R. V. Morris, G. Klingelhöfer, B. Bernhardt, C. Schröder2 D. S. Rodionov, P. A. de Souza, Jr., A. Yen, R. Gellert, E. N. Evlanov, J. Foh, E. Kankeleit, P. Gütlich, D. W. Ming, F. Renz, T. Wdowiak, S. W. Squyres, R. E. Arvidson
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Mössbauer spectra measured on Mars by the Spirit rover during the primary mission are characterized by two ferrous iron doublets (olivine and probably pyroxene) and a ferric iron doublet (tentatively associated to nanophase ferric iron oxide). Two sextets resulting from nonstoichiometric magnetite are also present, except for a coating on the rock Mazatzal, where a hematite-like sextet is present. Greater proportions of ferric-bearing phases are associated with undisturbed soils and rock surfaces as compared to fresh rock surfaces exposed by grinding. The ubiquitous presence of olivine in soil suggests that physical rather than chemical weathering processes currently dominate at Gusev crater.
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| J. Geophys. Res., 108, 10.1029/2003|E002138 (2003)
The Athena MIMOS II Mössbauer Spectrometer Investigation
G. Klingelhöfer, R.V. Morris, B. Bernhardt, D. Rodionov, P. A. de Souza Jr., S. W. Squyres, J. Foh, E. Kankeleit, U. Bonnes, R. Gellert, Ch. Schröder, S. Linkin, E. Evlanov, B. Zubkov, and O. Prilutski
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Mössbauer spectroscopy is a powerful tool for quantitative mineralogical analysis of Fe-bearing materials. The miniature Mössbauer spectrometer MIMOS II is a component of the Athena science payload to be launched to Mars in 2003 on both Mars Exploration Rover missions. The instrument has two major components: (1) a rover-based electronics board which contains power supplies, a dedicated central processing unit, memory, and associated support electronics and (2) a sensor head that is mounted at the end of the instrument deployment device (IDD) for placement of the instrument in physical contact with soil and rock. The velocity transducer operates at a nominal frequency of ~25 Hz and is configured with two 57Co/Rh Mössbauer sources. One source (~5 mCi landed intensity), together with a reference target (hematite plus a-Fe) and PIN diode detector in transmission geometry, are internal to the sensor head and is used for instrument calibration. The other source (~150 mCi landed intensity), together with four PIN diodes in backscatter measurement geometry, irradiates Martian surface materials with a beam diameter of ~1.4 cm after passing through a collimator. Physical contact with surface materials is sensed with a switch-activated contact plate. The contact plate and internal reference target are instrumented with temperature sensors. Assuming ~18% Fe for Martian surface materials, experiment time is 6-12 hours during the night for quality spectra (i.e., good counting statistics); 1-2 hours is sufficient to identify and quantify the most abundant Fe-bearing phases. Data stored internal to the instrument for selectable return to Earth include Mössbauer and pulse-height analysis spectra (256 channels each) for each of the five detectors in up to 13 temperature intervals (65 Mössbauer spectra), engineering data for the velocity transducer, and temperature measurements. The total data volume is ~150 kByte. The mass and power consumption are ~500 g (~400g for the sensor head) and ~2 W, respectively.
The scientific measurement objectives of the Mössbauer investigation are to obtain for rock, soil, and dust (1) the mineralogical identification of iron-bearing phases (e.g., oxides, silicates, sulfides, sulfates, and carbonates), (2) the quantitative measurement of the distribution of iron among these iron-bearing phases (e.g., the relative proportions of iron in olivine, pyroxenes, ilmenite and magnetite in a basalt), and (3) the quantitative measurement of the distribution of iron among its oxidation states (e.g., Fe2+, Fe3+, and Fe6+). Special geologic targets of the Mössbauer investigation are dust collected by the Athena magnets and exterior and interior rock and soil surfaces exposed by the Athena Rock Abrasion Tool and by trenching with rover wheels, respectively.
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Other MER Publications
| Nature 436, 49-54 (7 July 2005)
An integrated view of the chemistry and mineralogy of martian soils
Albert S. Yen, Ralf Gellert, Christian Schröder, Richard V. Morris, James F. Bell, III, Amy T. Knudson, Benton C. Clark, Douglas W. Ming, Joy A. Crisp, Raymond E. Arvidson, Diana Blaney, Johannes Brückner, Philip R. Christensen, David J. DesMarais, Paulo A. de Souza, Jr, Thanasis E. Economou, Amitabha Ghosh, Brian C. Hahn, Kenneth E. Herkenhoff, Larry A. Haskin, Joel A. Hurowitz, Bradley L. Joliff, Jeffrey R. Johnson, Göstar Klingelhöfer, Morten Bo Madsen, Scott M. McLennan, Harry Y. McSween, Lutz Richter, Rudi Rieder, Daniel Rodionov, Larry Soderblom, Steven W. Squyres, Nicholas J. Tosca, Alian Wang, Michael Wyatt and Jutta Zipfel
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The mineralogical and elemental compositions of the martian soil are indicators of chemical and physical weathering processes. Using data from the Mars Exploration Rovers, we show that bright dust deposits on opposite sides of the planet are part of a global unit and not dominated by the composition of local rocks. Dark soil deposits at both sites have similar basaltic mineralogies, and could reflect either a global component or the general similarity in the compositions of the rocks from which they were derived. Increased levels of bromine are consistent with mobilization of soluble salts by thin films of liquid water, but the presence of olivine in analysed soil samples indicates that the extent of aqueous alteration of soils has been limited. Nickel abundances are enhanced at the immediate surface and indicate that the upper few millimetres of soil could contain up to one per cent meteoritic material.
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| Nature 436, 62-65 (7 July 2005)
Indication of drier periods on Mars from the chemistry and mineralogy of atmospheric dust
Walter Goetz, Preben Bertelsen, Charlotte S. Binau, Haraldur P. Gunnlaugsson, Stubbe F. Hviid, Kjartan M. Kinch, Daniel E. Madsen, Morten B. Madsen, Malte Olsen, Ralf Gellert, Göstar Klingelhöfer, Douglas W. Ming, Richard V. Morris, Rudolf Rieder, Daniel S. Rodionov, Paulo A. de Souza, Jr, Christian Schrouml;der, Steve W. Squyres, Tom Wdowiak and Albert Yen
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The ubiquitous atmospheric dust on Mars is well mixed by periodic global dust storms, and such dust carries information about the environment in which it once formed and hence about the history of water on Mars. The Mars Exploration Rovers have permanent magnets to collect atmospheric dust for investigation by instruments on the rovers. Here we report results from Mössbauer spectroscopy and X-ray fluorescence of dust particles captured from the martian atmosphere by the magnets. The dust on the magnets contains magnetite and olivine; this indicates a basaltic origin of the dust and shows that magnetite, not maghemite, is the mineral mainly responsible for the magnetic properties of the dust. Furthermore, the dust on the magnets contains some ferric oxides, probably including nanocrystalline phases, so some alteration or oxidation of the basaltic dust seems to have occurred. The presence of olivine indicates that liquid water did not play a dominant role in the processes that formed the atmospheric dust.
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| Nature 436, 66-69 (7 July 2005)
Water alteration of rocks and soils on Mars at the Spirit rover site in Gusev crater
Larry A. Haskin, Alian Wang, Bradley L. Jolliff, Harry Y. McSween, Benton C. Clark, David J. Des Marais, Scott M. McLennan, Nicholas J. Tosca, Joel A. Hurowitz, Jack D. Farmer, Albert Yen, Steve W. Squyres, Raymond E. Arvidson, Göstar Klingelhöfer, Christian Schrouml;der, Paulo A. de Souza, Jr, Douglas W. Ming, Ralf Gellert, Jutta Zipfel, Johannes Brückner, James F. Bell, III, Kenneth Herkenhoff, Phil R. Christensen, Steve Ruff, Diana Blaney, Steven Gorevan, Nathalie A. Cabrol, Larry Crumpler, John Grant and Lawrence Soderblom
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Gusev crater was selected as the landing site for the Spirit rover because of the possibility that it once held a lake. Thus one of the rover's tasks was to search for evidence of lake sediments. However, the plains at the landing site were found to be covered by a regolith composed of olivine-rich basaltic rock and windblown 'global' dust. The analyses of three rock interiors exposed by the rock abrasion tool showed that they are similar to one another, consistent with having originated from a common lava flow. Here we report the investigation of soils, rock coatings and rock interiors by the Spirit rover from sol (martian day) 1 to sol 156, from its landing site to the base of the Columbia hills. The physical and chemical characteristics of the materials analysed provide evidence for limited but unequivocal interaction between water and the volcanic rocks of the Gusev plains. This evidence includes the softness of rock interiors that contain anomalously high concentrations of sulphur, chlorine and bromine relative to terrestrial basalts and martian meteorites; sulphur, chlorine and ferric iron enrichments in multilayer coatings on the light-toned rock Mazatzal; high bromine concentration in filled vugs and veins within the plains basalts; positive correlations between magnesium, sulphur and other salt components in trench soils; and decoupling of sulphur, chlorine and bromine concentrations in trench soils compared to Gusev surface soils, indicating chemical mobility and separation.
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| Science, Vol 306, Issue 5702, p.1709 (2004)
In Situ Evidence for an Ancient Aqueous Environment at Meridiani Planum, Mars
S. W. Squyres, J. P. Grotzinger, R. E. Arvidson, J. F. Bell, III, W. Calvin, P. R. Christensen, B. C. Clark, J. A. Crisp, W. H. Farrand, K. E. Herkenhoff, J. R. Johnson, G. Klingelhöfer, A. H. Knoll, S. M. McLennan, H. Y. McSween, Jr., R. V. Morris, J. W. Rice, Jr., R. Rieder, and L. A. Soderblom
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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.
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| Science, Vol 306, Issue 5702, p.1723 (2004)
Soils of Eagle Crater and Meridiani Planum at the Opportunity Rover Landing Site
L. A. Soderblom, R. C. Anderson, R. E. Arvidson, J. F. Bell, III, N. A. Cabrol, W. Calvin, P. R. Christensen, B. C. Clark, T. Economou, B. L. Ehlmann, W. H. Farrand, D. Fike, R. Gellert, T. D. Glotch, M. P. Golombek, R. Greeley, J. P. Grotzinger, K. E. Herkenhoff, D. J. Jerolmack, J. R. Johnson, B. Jolliff, G. Klingelhöfer, A. H. Knoll, Z. A. Learner, R. Li, M. C. Malin, S. M. McLennan, H. Y. McSween, D. W. Ming, R. V. Morris, J. W. Rice, Jr., L. Richter, R. Rieder, D. Rodionov, C. Schröder, F. P. Seelos, IV, J. M. Soderblom, S. W. Squyres, R. Sullivan, W. A. Watters, C. M. Weitz, M. B. Wyatt, A. Yen, and J. Zipfel
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The soils at the Opportunity site are fine-grained basaltic sands mixed with dust and sulfate-rich outcrop debris. Hematite is concentrated in spherules eroded from the strata. Ongoing saltation exhumes the spherules and their fragments, concentrating them at the surface. Spherules emerge from soils coated, perhaps from subsurface cementation, by salts. Two types of vesicular clasts may represent basaltic sand sources. Eolian ripples, armored by well-sorted hematite-rich grains, pervade Meridiani Planum. The thickness of the soil on the plain is estimated to be about a meter. The flatness and thin cover suggest that the plain may represent the original sedimentary surface.
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