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Jutta ZIPFEL Bradley L. JOLLIFF Ralf GELLERT Kenneth E. HERKENHOFF Rudolf RIEDER Robert ANDERSON James F. BELL III Johannes BRÜCKNER Joy A. CRISP Philip R. CHRISTENSEN Benton C. CLARK Paulo A.
De SOUZA Jr. Gerlind DREIBUS Claude
D’USTON Thanasis ECONOMOU Steven P. GOREVAN Brian C. HAHN Göstar KLINGELHÖFER Timothy J. McCOY Harry Y. McSWEEN Jr. Douglas W. MING Richard V. MORRIS Daniel S. RODIONOV Steven W. SQUYRES Heinrich WÄNKE Shawn P. WRIGHT Michael B. WYATT Albert S. YEN 《Meteoritics & planetary science》2011,46(1):1-20
Abstract– The Opportunity rover of the Mars Exploration Rover mission encountered an isolated rock fragment with textural, mineralogical, and chemical properties similar to basaltic shergottites. This finding was confirmed by all rover instruments, and a comprehensive study of these results is reported here. Spectra from the miniature thermal emission spectrometer and the Panoramic Camera reveal a pyroxene‐rich mineralogy, which is also evident in Mössbauer spectra and in normative mineralogy derived from bulk chemistry measured by the alpha particle X‐ray spectrometer. The correspondence of Bounce Rock’s chemical composition with the composition of certain basaltic shergottites, especially Elephant Moraine (EET) 79001 lithology B and Queen Alexandra Range (QUE) 94201, is very close, with only Cl, Fe, and Ti exhibiting deviations. Chemical analyses further demonstrate characteristics typical of Mars such as the Fe/Mn ratio and P concentrations. Possible shock features support the idea that Bounce Rock was ejected from an impact crater, most likely in the Meridiani Planum region. Bopolu crater, 19.3 km in diameter, located 75 km to the southwest could be the source crater. To date, no other rocks of this composition have been encountered by any of the rovers on Mars. The finding of Bounce Rock by the Opportunity rover provides further direct evidence for an origin of basaltic shergottite meteorites from Mars. 相似文献
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Gerlind Dreibus 《Icarus》2004,167(1):166-169
High phosphorus concentrations in the range of 0.5 wt% in rocks and soil have been measured on the martian surface, terrestrial P concentrations are far less uniform and generally lower. Reactions of terrestrial basalt and granite powders with phosphate solution result in an enrichment of phosphorus in both, with basalt having a far better reactivity than granite. The implications of these results for P on Mars are discussed. 相似文献
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Gerlind DREIBUS Reinhard HAUBOLD Wolfgang HUISL Bernhard SPETTEL 《Meteoritics & planetary science》2008,43(11):1895-1908
Abstract— The mobilization of K, rare earth elements (REE), Th, and U from Martian surface material upon contact with acidic solutions probably occurred extensively on Mars about 4 to 3.5 Ga ago and seems to have occurred locally in more recent times. We have studied the dissolution of these elements by leaching the basaltic shergottite Zagami and the terrestrial basalt BE‐N at constant pH values ranging from 5 to 1 in the absence and presence of added salts. Potassium is nearly immobile in Zagami and mobilized readily from BE‐N. The REE reside mostly in calcium phosphates and dissolve readily, with those in whitlockite of Zagami reacting slightly better than those in apatite of BE‐N. Thorium and U also reside mostly in calcium phosphates. Both dissolve similarly for both basalts and less readily than the REE. The experiments indicate the extent of the mobilization of K, REE, Th, and U, when acidic water leached the surface of Mars. Potassium was released slowly and in a small relative amount. The REE, and particularly the LREE, became mobile readily and were possibly distributed over large areas before immobilization. Thorium and U dissolved more slowly than the REE and were distributed less widely. 相似文献
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Gerlind DREIBUS Reinhard HAUBOLD Wolfgang HUISL Bernhard SPETTEL 《Meteoritics & planetary science》2007,42(6):951-962
Abstract Terrestrial alteration of meteorites results in the redistribution, gain, or loss of uranium and other elements. We have measured the maximum U adsorption capacity of a meteorite and two geochemical reference materials under conditions resembling terrestrial ones (pH 5.8). The basaltic eucrite Sioux County adsorbs 7 ppm of U. The result for the terrestrial granite AC‐E is similar (5 ppm), while the basalt BE‐N adsorbs 34 ppm of U. We have also investigated U adsorption in the presence of phosphate (0.01 M or less) in imitation of conditions that probably occurred in the earlier history of Mars. Such a process would have alterated Martian surface material and would be noticeable in Martian meteorites from the affected surface. The experiments demonstrated the counteracting effects of phosphate, which increases U adsorption, but decreases the quantity of dissolved U that is available for adsorption. U adsorption by AC‐E increases to 7 ppm. The lowered value for BE‐N of 8 ppm results from the low quantity of dissolved U in the volume of solution used. The results from the adsorption experiments and from leaching the Martian meteorite Zagami and a terrestrial basalt imply that the aqueous redistribution of U on Mars was moderate. Acidic liquids mobilized uranium and other metals, but present phosphate impeded the dissolution of U compounds. Some mobilized U may have reached the global sinks, while most of it probably was transported in the form of suspended particles over a limited distance and then settled. 相似文献
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The computation of sparse representations of data on the sphere (e.g. topographical data) is a crucial step for further processing
such as multiple separation, migration, imaging and sparsity promoting data-recovery. The Easy Path Wavelet Transform (EPWT)
is a new tool for sparse data representation that has recently been introduced for image compression. In this paper we consider
the EPWT on spherical triangulations. It is a locally adaptive transform that works along pathways through the array of function
values and exploits the local correlations of the data in a simple appropriate manner. In our approach the usual discrete
one-dimensional orthogonal or biorthogonal wavelet transform can be applied. The EPWT can be used for defining a multiresolution
analysis on the sphere in which the scaling spaces and the wavelet spaces depend adaptively on the data. Issues of implementation
of the EPWT are also considered. 相似文献
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J. ZIPFEL A. BISCHOFF L. SCHULTZ B. SPETTEL G. DREIBUS T. SCHÖNBECK H. PALME 《Meteoritics & planetary science》2010,45(9):1488-1501
Abstract– We present a detailed study of mineralogy, chemistry, and noble gases of the Neuschwanstein (EL6) chondrite that fell in 2002 in southern Germany. The meteorite has an unbrecciated texture and exhibits only minor shock features. Secondary weathering products are marginal. Neuschwanstein is an EL6 chondrite with heterogeneously distributed metal and sulfide grains. In terms of bulk chemistry, it has very high Fe concentrations, and siderophile and halogen element abundances higher than typical EL chondrites. However, like other ELs of higher petrologic type, it has low moderately volatile element abundances, e.g., Mn and Zn. We interpret these as indicators for loss of sulfide, probably through mobilization of ferroan alabandite and a Zn‐bearing sulfide, potentially sphalerite, during metamorphism. Trapped noble gases are dominated by a subsolar component with high Ar concentrations and are typical for EL chondrites. The shielding parameters indicate a small meteoroid (<20 cm radius) with an exposure age of approximately 47 Ma, which is among the highest for enstatite chondrites. 相似文献
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J. ZIPFEL P. SCHERER B. SPETTEL G. DREIBUS L. SCHULTZ 《Meteoritics & planetary science》2000,35(1):95-106
Abstract— In 1998, Dar al Gani (DaG) 476 was found in the Libyan desert. The meteorite is classified as a basaltic shergottite and is only the 13th martian meteorite known to date. It has a porphyritic texture consisting of a fine‐grained groundmass and larger olivines. The groundmass consists of pyroxene and feldspathic glass. Minor phases are oxides and sulfides as well as phosphates. The presence of olivine, orthopyroxene, and chromite is a feature that DaG 476 has in common with lithology A of Elephant Moraine (EET) A79001. However, in DaG 476, these phases appear to be early phenocrysts rather than xenocrysts. Shock features, such as twinning, mosaicism, and impact‐melt pockets, are ubiquitous. Terrestrial weathering was severe and led to formation of carbonate veins following grain boundaries and cracks. With a molar MgO/(MgO + FeO) of 0.68, DaG 476 is the most magnesian member among the basaltic shergottites. Compositions of augite and pigeonite and some of the bulk element concentrations are intermediate between those of lherzolitic and basaltic shergottites. However, major elements, such as Fe and Ti, as well as LREE concentrations are considerably lower than in other shergottites. Noble gas concentrations are low and dominated by the mantle component previously found in Chassigny. A component, similar to that representing martian atmosphere, is virtually absent. The ejection age of 1.35 ± 0.10 Ma is older than that of EETA79001 and could possibly mark a distinct ejection. Dar al Gani 476 is classified as a basaltic shergottite based on its mineralogy. It has a fine‐grained groundmass consisting of clinopyroxene, pigeonite and augite, feldspathic glass and chromite, Ti‐chromite, ilmenite, sulfides, and whitlockite. Isolated olivine and single chromite grains occur in the groundmass. Orthopyroxene forms cores of some pigeonite grains. Shock‐features, such as shock‐twinning, mosaicism, cracks, and impact‐melt pockets, are abundant. Severe weathering in the Sahara led to significant formation of carbonate veins crosscutting the entire meteorite. Dar al Gani 476 is distinct from other known shergottites. Chemically, it is the most magnesian member among known basaltic shergottites and intermediate in composition for most trace and major elements between Iherzolitic and basaltic shergottites. Unique are the very low bulk REE element abundances. The CI‐normalized abundances of LREEs are even lower than those of Iherzolitic shergottites. The overall abundance pattern, however, is similar to that of QUE 94201. Textural evidence indicates that orthopyroxene, as well as olivine and chromite, crystallized as phenocrysts from a magma similar in composition to that of bulk DaG 476. Whether such a magma composition can be a shergottite parent melt or was formed by impact melting needs to be explored further. At this time, it cannot entirely be ruled out that these phases represent relics of disaggregated xenoliths that were incorporated and partially assimilated by a basaltic melt, although the texture does not support this possibility. Trapped noble gas concentrations are low and dominated by a Chassigny‐like mantle component. Virtually no martian atmosphere was trapped in DaG 476 whole‐rock splits. The exposure age of 1.26 ± 0.09 Ma is younger than that of most shergottites and closer to that of EETA79001. The ejection age of 1.35 ± 0.1 Ma could mark another distinct impact event. 相似文献
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