共查询到20条相似文献，搜索用时 31 毫秒
1.
《Meteoritics & planetary science》2015,50(10):i-ii
X‐ray map of a thin section of a sample of the Chelyabinsk meteorite from the study of Righter et al. (pp. 1790–1819). Sample Chel‐102 contains roughly 50 modal% of a dark lithology that is shock‐darkened LL5 chondrite (left side of image). There is heavy veining of this portion, and very little original equilibrated chondritic texture remaining. The other 50% of Chel‐102 (right side of image) is a very fi ne‐grained melt breccia comprised of mesostasis (85%), metal‐troilite droplets (5%), and chondritic fragments of similar mineralogy to the light lithology of Chel‐101. Image produced by Eve. L. Berger. 相似文献
2.
《Meteoritics & planetary science》2012,47(12):i-i
Cover: Background–Orion Nebula; bottom left corner–combined elemental map in Mg (red), Ca (green), and Al Kα X–rays of a compound ultrarefractory CAI–bearing inclusion from the reduced CV3 carbonaceous chondrite Efremovka. The CAI consists of a Fluffy Type A inclusion, an ultrarefractory inclusion, and an amoeboid olivine aggregate (see paper by Ivanova et al. on p. 2107). 相似文献
3.
《Meteoritics & planetary science》2015,50(9):i-i
BSE image of a polished thick section EET 87720,41 containing an igneous‐textured granitic clast, prepared from an interior chip of a polymict ureilite EET 87720. The clast is not indigenous to the ureilite parent body, but it provides evidence for the formation of evolved melts on an unknown parent body (a volatile‐rich parent body perhaps resembling early Mars) in the early solar system. The scale bar size is 1 mm. Andrew Beard et al. describe the clast in detail in their paper on pp. 1613–1623. (Image courtesy of A. Beard). 相似文献
4.
Hyperspectral mapping of alteration assemblages within a hydrothermal vug at the Haughton impact structure,Canada 
下载免费PDF全文
下载免费PDF全文 Rebecca N. Greenberger John F. Mustard Gordon R. Osinski Livio L. Tornabene Alexandra J. Pontefract Cassandra L. Marion Roberta L. Flemming Janette H. Wilson Edward A. Cloutis 《Meteoritics & planetary science》2016,51(12):2274-2292
Meteorite impacts on Earth and Mars can generate hydrothermal systems that alter the primary mineralogies of rocks and provide suitable environments for microbial colonization. We investigate a calcite–marcasite‐bearing vug at the ~23 km diameter Haughton impact structure, Devon Island, Nunavut, Canada, using imaging spectroscopy of the outcrop in the field (0.65–1.1 μm) and samples in the laboratory (0.4–2.5 μm), point spectroscopy (0.35–2.5 μm), major element chemistry, and X‐ray diffraction analyses. The mineral assemblages mapped at the outcrop include marcasite; marcasite with minor gypsum and jarosite; fibroferrite and copiapite with minor gypsum and melanterite; gypsum, Fe3+ oxides, and jarosite; and calcite, gypsum, clay, microcline, and quartz. Hyperspectral mapping of alteration phases shows spatial patterns that illuminate changes in alteration conditions and formation of specific mineral phases. Marcasite formed from the postimpact hydrothermal system under reducing conditions, while subsequent weathering oxidized the marcasite at low temperatures and water/rock ratios. The acidic fluids resulting from the oxidation collected on flat‐lying portions of the outcrop, precipitating fibroferrite + copiapite. That assemblage then likely dissolved, and the changing chemistry and pH resulting from interaction with the calcite‐rich host rock formed gypsum‐bearing red coatings. These results have implications for understanding water–rock interactions and habitabilities at this site and on Mars. 相似文献
5.
《Meteoritics & planetary science》2014,49(5):i-i
Calcium X‐ray elemental map of a strongly hydrated microclast in the Rumuruti chondrite Northwest Africa 6828. The clast is crosscut by irregular Ca‐carbonate‐filled fractures that do not extend into the host meteorite. It represents the first hydrous fragment found in an R chondrite and documents the wide distribution of water‐bearing material in the solar system. Image was collected using the JEOL JXA 8500F field emission cathode electron microprobe at the Museum für Naturkunde, Berlin. For details, see the article by Ansgar Greshake, pp. 824–841. 相似文献
6.
The solar activity can be quantified by solar modulation parameter Φ that affects the heliospheric magnetic field. This activity influences the intensity of the galactic cosmic ray (GCR) particle flux within the solar system, and consequently, the differential primary particle spectra depend on the solar modulation parameter Φ (MeV). The modulation parameter Φ shows spatial and temporal variations (Leya and Masarik 2009). Some of the solar activity variations are cyclic and result in measurable effects as for example the 11‐year solar cycle. Variations in solar activity only induce small effects on the production of long‐lived cosmogenic radionuclides. This is due to the fact that activities measured in meteorites usually correspond to saturation values and represent long‐term average values. Long‐lived radionuclides often require millions of years of irradiation by GCR to reach saturation and therefore activity cycles average out. In contrast, one can expect strongly pronounced variations for saturation values caused by primary flux intensity variations, if short‐lived radionuclides with half‐lives ranging from days to a few years are investigated. Short‐lived cosmogenic nuclides were the subject of many experimental and theoretical investigations (e.g., Evans et al. 1982; Spergel et al. 1986; Neumann et al. 1997; Komura et al. 2002; Laubenstein et al. 2012). The aim of this work is to develop formulae for calculating production rates of radionuclides with short half‐life, taking into account temporal variations in the primary cosmic ray intensity. The developed formulae were applied to the Kosice and Chelyabinsk meteorites. The results for the Ko?ice meteorite were already published (Povinec et al. 2015). Here, we give a full explanation of underlying model. 相似文献
7.
《Meteoritics & planetary science》2015,50(8):i-i
Phase map of an iddingsite vein in an olivine grain from the Nakhla meteorite made using multiple linear least squares fitting of electron energy loss spectroscopy data (green ‐ olivine, blue ‐ siderite, pink ‐ ferric oxyhydroxide, orange ‐ Fe‐Mg silicate). The detailed structure of the Fe‐Mg silicate is shown in the inset, which is a spectroscopic map of iron (red), magnesium (green) and silicon (blue) showing the nanoscale structure of opal‐A spheres in a Fe‐Mg‐rich matrix. Martin Lee et al. discuss the details in their article on pp. 1362–1377. Image prepared by Ian MacLaren. 相似文献
8.
‘Rootless’ debris cones (or pseudocraters) occur in platy, patterned ground throughout the Cerberus plains of Mars and are thought to represent the products of explosive magma-ice interaction [Lanagan et al., 2001. Geophys. Res. Lett. 28, 2365-2368; Fagents et al., 2002. In: Smellie, J.L., Chapman, M.G. (Eds.), Volcano-Ice Interaction on Earth and Mars. In: Geol. Soc. Spec. Publ., vol. 202, pp. 295-317]. Requiring lava and water interspersed, they are central to theories of multiple magmatic and aqueous flood events [Burr et al., 2002. Icarus 159, 53-73; Berman, D.C., Hartmann, W.K., 2002. Icarus 159, 1-17] and widespread sheet volcanism [Keszthelyi et al., 2000. J. Geophys. Res. 105, 15027-15049] in the region during the late Amazonian (a region reported to have been occupied by water bodies ranging from lakes to oceans [Scott et al., 1995. Map of Mars showing channels and possible paleolake basins. USGS Miscellaneous Investigations Series, Map I-2461 (1:30,000,000)]). The nature of the platy substrate is the subject of debate, with evidence given for lava [Keszthelyi et al., 2000. J. Geophys. Res. 105, 15027-15049; Plescia, J.B., 2003. Icarus 164, 79-95] and ice [Brakenridge, G.R., 1993. Lunar Planet. Sci. XXIV (Part 1), 175-176; Rice et al., 2002. Lunar Planet. Sci. XXXIII. Abstract #2026; Murray et al., 2005. Nature 434, 352-355]. The superposition relationships of cones and platy deposits in the channels of the Athabasca Valles precludes a magmatic origin, indicating later formation as permafrost mounds (or ‘pingos’), with implications for geologically recent flood volcanism, age constraints on young surfaces and recent climate change on Mars. 相似文献
9.
D. Koutroumpa 《Astronomische Nachrichten》2012,333(4):341-346
About 15 years ago, charge exchange (CX) X‐ray emission was discovered in comet observations, and was identified as the radiative decay of excited states of highly‐charge solar wind ions populated in collisions with neutral cometary material. This non‐thermal X‐ray emission mechanism is now generally acknowledged in planetary environments (e.g. Mars, Earth), as well as interstellar atoms sweeping through the heliosphere. In this paper I present the most recent improvements made in simulations of the heliospheric CX X‐ray emission. The model results are compared to X‐ray data from Suzaku, XMM‐Newton and Chandra spanning over a 10‐year period, and some conclusions are drawn on the heliospheric contribution to the diffuse soft X‐ray background. The solar system CX X‐ray sources can serve as prototypes in terms of modeling and diagnostics to more distant astrophysical objects where CX emission signatures are being discovered (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
10.
《Meteoritics & planetary science》2014,49(7):i-i
Left image: Composite backscattered electron image of Paris‐6, one of the three sections of Paris surveyed by Yves Marrocchi et al. in their study. Right image: Composite EDX elemental map of Mg (red), Al (blue), and Ca (green) of Paris‐6 revealing the distribution of chondrules, CAIs, and matrix. For details their article on pp. 1232–1249. Image courtesy of Anton T. Kearsley. 相似文献
11.
T. D. SWINDLE A. H. TREIMAN D. J. LINDSTROM M. K. BURKLAND B. A. COHEN J. A. GRIER B. LI E. K. OLSON 《Meteoritics & planetary science》2000,35(1):107-115
Abstract— We analyzed noble gases from 18 samples of weathering products (“iddingsite”) from the Lafayette meteorite. Potassium‐argon ages of 12 samples range from near zero to 670 ± 91 Ma. These ages confirm the martian origin of the iddingsite, but it is not clear whether any or all of the ages represent iddingsite formation as opposed to later alteration or incorporation of martian atmospheric 40Ar. In any case, because iddingsite formation requires liquid water, this data requires the presence of liquid water near the surface of Mars at least as recently as 1300 Ma ago, and probably as recently as 650 Ma ago. Krypton and Xe analysis of a single 34 μg sample indicates the presence of fractionated martian atmosphere within the iddingsite. This also confirms the martian origin of the iddingsite. The mechanism of incorporation could either be through interaction with liquid water during iddingsite formation or a result of shock implantation of adsorbed atmospheric gas. Our strongest conclusion is that the iddingsite in Lafayette formed on Mars, in agreement with the microstratigraphic arguments of Gooding et al. (1991) and Treiman et al. (1993). A preterrestrial origin of the iddingsite is required both by the many non‐zero K‐Ar ages and by the presence of Xe that is isotopically distinct from any terrestrial Xe. The Xe is accompanied by Kr, but the Kr and Xe have been fractionated if they are derived from the present martian atmosphere. This is presumably the result of either incorporation via interaction with liquid water (Drake et al., 1994; Bogard and Garrison, 1998) or by adsorption from the martian atmosphere, perhaps accompanied by shock (see also Gilmour et al., 1998, 1999). Although the iddingsite is enriched in Kr and Xe compared to whole‐rock analyses, it is not clear whether iddingsite is the dominant carrier of the atmospheric‐derived gas (Drake et al., 1994) or merely a minor carrier (Gilmour et al., 1999). Our 40Ar‐39Ar experiment was disappointing, in that it mostly served to confirm that the iddingsite, which contains fine‐grained clays, is susceptible to recoil loss of 39Ar during irradiation. Only one sample of five gave a clear signal of radiogenic or extraterrestrial 40Ar, and that was only by 3°. Potassium‐argon ages of the second set of samples were more successful, ranging from near 0 to 670 ± 91 Ma. It is not clear whether any or all of the ages represent iddingsite formation, as opposed to later alteration. The fact that a Rb‐Sr experiment (Shih et al., 1998) gave an apparent age for iddingsite of 679 ± 66 Ma (2a) suggests that perhaps formation of iddingsite occurred (or began) ～650 Ma ago and that some samples either formed, or were thermally altered, later. The ages could be even younger than 650 Ma, if the samples have incorporated martian atmospheric 40Ar. This means that liquid water was certainly present on Mars in the last 1300 Ma (the formation age of Lafayette), and probably within the last 650 Ma. 相似文献
12.
Axel Wittmann Randy L. Korotev Bradley L. Jolliff Anthony J. Irving Desmond E. Moser Ivan Barker Douglas Rumble III 《Meteoritics & planetary science》2015,50(2):326-352
The Northwest Africa (NWA) 7475 meteorite is one of the several stones of paired regolith breccias from Mars based on petrography, oxygen isotope, mineral compositions, and bulk rock compositions. Its inventory of lithic clasts is dominated by vitrophyre impact melts that were emplaced while they were still molten. Other clast types include crystallized impact melt rocks, evolved plutonic rocks, possible basalts, contact metamorphosed rocks, and siltstones. Impact spherules and vitrophyre shards record airborne transport, and accreted dust rims were sintered on most clasts, presumably during residence in an ejecta plume. The clast assemblage records at least three impact events, one that formed an impact melt sheet on Mars ≤4.4 Ga ago, a second that assembled NWA 7475 from impactites associated with the impact melt sheet at 1.7–1.4 Ga, and a third that launched NWA 7475 from Mars ~5 Ma ago. Mildly shocked pyroxene and plagioclase constrain shock metamorphic conditions during launch to >5 and <15 GPa. The mild postshock‐heating that resulted from these shock pressures would have been insufficient to sterilize this water‐bearing lithology during launch. Magnetite, maghemite, and pyrite are likely products of secondary alteration on Mars. Textural relationships suggest that calcium‐carbonate and goethite are probably of terrestrial origin, yet trace element chemistry indicates relatively low terrestrial alteration. Comparison of Mars Odyssey gamma‐ray spectrometer data with the Fe and Th abundances of NWA 7475 points to a provenance in the ancient southern highlands of Mars. Gratteri crater, with an age of ~5 Ma and an apparent diameter of 6.9 km, marks one possible launch site of NWA 7475. 相似文献
13.
《Astronomische Nachrichten》2012,333(4)
The detector plane of the prototype of a global soft X‐ray imaging instrument for heliophysics, planetary science, and astrophysics (see M.R. Collier et al., this issue, p. 378) 相似文献
14.
Nova V5116 Sgr 2005 No. 2, discovered on 2005 July 4, was observed with XMM‐Newton in March 2007, 20 months after the optical outburst. The X‐ray spectrum showed that the nova had evolved to a pure supersoft X‐ray source, indicative of residual H‐burning on top of the white dwarf. The X‐ray light‐curve shows abrupt decreases and increases of the flux by a factor 8 with a periodicity of 2.97 h, consistent with the possible orbital period of the system. The EPIC spectra are well fit with an ONe white dwarf atmosphere model, with the same temperature both in the low and the high flux periods. This rules out an intrinsic variation of the X‐ray source as the origin of the flux changes, and points to a possible partial eclipse as the origin of the variable light curve. The RGS high resolution spectra support this scenario showing a number of emission features in the low flux state, which either disappear or change into absorption features in the high flux state. A new XMM‐Newton observation in March 2009 shows the SSS had turned off and V51 16 Sgr had evolved into a weaker and harder X‐ray source (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
15.
I.P. Robertson T.E. Cravens D.G. Sibeck M.R. Collier K.D. Kuntz 《Astronomische Nachrichten》2012,333(4):309-312
On 2001 March 31 a coronal mass ejection pushed the subsolar magnetopause to the vicinity of geosynchronous orbit at 6.6 RE. The NASA/GSFC Community Coordinated Modeling Center (CCMC) employed a global magnetohydrodynamic (MHD) model to simulate the solar wind‐magnetosphere interaction during the peak of this geomagnetic storm. Robertson et al. then modeled the expected soft X‐ray emission due to solar wind charge exchange with geocoronal neutrals in the dayside cusp and magnetosheath. The locations of the bow shock, magnetopause and cusps were clearly evident in their simulations. Another geomagnetic storm took place on 2000 July 14 (Bastille Day). We again modeled X‐ray emission due to solar wind charge exchange, but this time as observed from a moving spacecraft. This paper discusses the impact of spacecraft location on observed X‐ray emission and the degree to which the locations of the bow shock and magnetopause can be detected in images (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
16.
A. Georgakakis 《Astronomische Nachrichten》2008,329(2):174-177
This paper shows that our understanding of the statistical properties of X‐ray selected normal galaxies (e.g. X‐ray luminosity function) can be significantly improved by combining a wide‐area XMM‐Newton survey with the moderare resolution and high S/N optical spectroscopy of the SDSS. Such a combined dataset has the potential to minimise uncertainties that affect existing normal galaxy samples at X‐rays, such as small number statistics, cosmic variance, AGN contamination and incompleteness at bright X‐ray luminosities. It is demonstrated that a 100 deg2 XMM‐Newton survey in the SDSS area to the limit fX(0.5–2 keV) ≈ 5 × 10–15 erg cm–2 s–1 will detect over 400 X‐ray selected normal galaxies with excellent control over systematic biases, thereby providing tight contraints on the X‐ray luminosity function at z ≈ 0.1. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
17.
We have determined the depth/diameter ratio for 87 craters on Mars using Mariner 9 UVS spectrometer altimetry (Barth et al., 1974). Our sample includes craters 12 to 100 km in diameter, and 0.4 to 3.3 km in depth. The largest depth/diameter ratios on Mars are comparable to those of fresh craters on Mercury (measured by Gault et al., 1975). However, more than half of our sample consists of degraded craters whose depths are significantly shallower than those of fresh craters of similar diameter on Mercury, confirming the interpretations of earlier photoanalysts. 相似文献
18.
As a result of feedback from massive stars, via their intense winds and/or supernova explosions, massive star‐forming regions are entirely filled with hot, X‐ray emitting plasmas, which escape into the ambient ISM. As shown recently by Townsley et al. for several “extreme” cases (Carina, M17, NGC 3576, NGC 3603, 30 Dor), by way of large Chandra ACIS mosaics, extra, non‐thermal emission lines are present on top of the standard lines emitted by hot plasmas. Some of them are very close to lines characteristic of charge‐exchange reactions between the hot plasma and the cold surrounding material, suggesting that this mechanism operates on large spatial scales (several 10 pc) in star‐forming regions in general. The connection with starburst galaxies is briefly mentioned, and it is pointed out that supernovae interacting with molecular clouds may also provide a good environment to look for charge exchange processes (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
19.
《Meteoritics & planetary science》2017,52(4):1-1
Cover: Residual gravity anomaly map (displayed in relief) of the Cerro do Jarau structure. Bruno B. Giacomini et al. discuss the structure in their article on pp. 565–583 . Image courtesy of Bruno B. Giacomini and Emilson P. Leite. 相似文献