排序方式： 共有39条查询结果，搜索用时 171 毫秒
1.
Paolo S. Garofalo Mattias B. Fricker Detlef Günther Paolo Forti Anna-Maria Mercuri Mara Loreti Bruno Capaccioni 《Earth and Planetary Science Letters》2010,289(3-4):560-569
Three hypogenic caves within the Naica mine of Mexico (Cueva de los Cristales — CLC, Ojo de la Reina — OR, and Cueva de las Velas — CLV) host spectacular gypsum crystals up to 11 m in length. These caves are close to another shallow cave of the area (Cueva de las Espadas — CLE), with which they cover a 160 m-deep vertical section of the local drainage basin. Similar to other hypogenic caves, all these caves lack a direct connection with the land surface and should be unrelated with climate.A record of multi-technique fluid inclusion data and pollen spectra from cave and mine gypsum indicates surprisingly that climatic changes occurring at Naica could have controlled fluid composition in these caves, and hence crystal growth. Microthermometry and LA-ICP-Mass Spectrometry of fluid inclusions indicate that the shallow, chemically peculiar, saline fluid (up to 7.7 eq. wt.%NaCl) of CLE could have formed from evaporation, during a dry and hot climatic period. The fluid of the deep caves was instead of low salinity (～ 3.5 eq. wt.% NaCl) and chemically homogeneous, and was poorly affected by evaporation. We propose that mixing of these two fluids, generated at different depths of the Naica drainage basin, determined the stable supersaturation conditions for the gigantic gypsum crystals to grow. Fluid mixing was controlled by the hydraulic communication between CLE and the other deep caves, and must have taken place during cycles of warm-dry and fresh-wet climatic periods, which are known to have occurred in the region. Pollen grains from a 35 ka-old gypsum crystal of CLC corresponds to a fairly homogenous catchment basin made of a mixed broadleaf wet forest, which suggests precipitation during a fresh-wet climatic period and confirms our interpretation of the fluid inclusion data.The unusual combination of geological and geochemical factors of Naica suggests that other hypogenic caves found elsewhere may not host similar crystals. However, this work shows that fluid inclusions and pollen spectra represent a useful tool for cave studies in general, and if used in future studies might be essential to unravel the mechanisms of hypogenic deposition. 相似文献
2.
R.H. Brown K.H. Baines J.-P. Bibring F. Capaccioni R.N. Clark D.P. Cruikshank V. Formisano Y. Langevin T.B. McCord V. Mennella P.D. Nicholson C. Sotin M.A. Chamberlain G. Hansen M. Showalter 《Icarus》2003,164(2):461-470
The Cassini Visual and Infrared Mapping Spectrometer (VIMS) is an imaging spectrometer covering the wavelength range 0.3-5.2 μm in 352 spectral channels, with a nominal instantaneous field of view of 0.5 mrad. The Cassini flyby of Jupiter represented a unique opportunity to accomplish two important goals: scientific observations of the jovian system and functional tests of the VIMS instrument under conditions similar to those expected to obtain during Cassini's 4-year tour of the saturnian system. Results acquired over a complete range of visual to near-infrared wavelengths from 0.3 to 5.2 μm are presented. First detections include methane fluorescence on Jupiter, a surprisingly high opposition surge on Europa, the first visual-near-IR spectra of Himalia and Jupiter's optically-thin ring system, and the first near-infrared observations of the rings over an extensive range of phase angles (0-120°). Similarities in the center-to-limb profiles of H+3 and CH4 emissions indicate that the H+3 ionospheric density is solar-controlled outside of the auroral regions. The existence of jovian NH3 absorption at 0.93 μm is confirmed. Himalia has a slightly reddish spectrum, an apparent absorption near 3 μm, and a geometric albedo of 0.06±0.01 at 2.2 μm (assuming an 85-km radius). If the 3-μm feature in Himalia's spectrum is eventually confirmed, it would be suggestive of the presence of water in some form, either free, bound, or incorporated in layer-lattice silicates. Finally, a mean ring-particle radius of 10 μm is found to be consistent with Mie-scattering models fit to VIMS near-infrared observations acquired over 0-120° phase angle. 相似文献
3.
Michelangelo Formisano Costanzo Federico Diego Turrini Angioletta Coradini Fabrizio Capaccioni Maria Cristina De Sanctis Cristina Pauselli 《Meteoritics & planetary science》2013,48(11):2316-2332
In this work, we study the link between the evolution of the internal structure of Vesta and thermal heating due to 26Al and 60Fe and long‐lived radionuclides, taking into account the chemical differentiation of the body and the affinity of 26Al with silicates. We explored several thermal and structural scenarios differing in the available strength of energy due to the radiogenic heating and in the postsintering macroporosity. By comparing them with the data supplied by the HEDs and the Dawn NASA mission, we use our results to constrain the accretion and differentiation time as well as the physical properties of the core. Differentiation takes place in all scenarios in which Vesta completes its accretion in <1.4 Ma after the injection of 26Al into the solar nebula. In all those scenarios where Vesta completes its formation in <1 Ma from the injection of 26Al, the degree of silicate melting reaches 100 vol% throughout the whole asteroid. If Vesta completed its formation between 1 and 1.4 Ma after 26Al injection, the degree of silicate melting exceeds 50 vol% over the whole asteroid, but reaches 100 vol% only in the hottest, outermost part of the mantle in all scenarios where the porosity is lower than 5 vol%. If the formation of Vesta occurred later than 1.5 Ma after the injection of 26Al, the degree of silicate melting is always lower than 50 vol% and is limited only to a small region of the asteroid. The radiation at the surface dominates the evolution of the crust, which ranges in thickness from 8 to about 30 km after 5 Ma: a layer about 3–20 km thick is composed of primitive unmelted chondritic material, while a layer of about 5–10 km is eucritic. 相似文献
4.
S. Keihm F. Tosi L. Kamp F. Capaccioni S. Gulkis D. Grassi M. Hofstadter G. Filacchione S. Lee S. Giuppi M. Janssen M. Capria 《Icarus》2012,221(1):395-404
The European Space Agency’s Rosetta spacecraft is the first Solar System mission to include instrumentation capable of measuring planetary thermal fluxes at both near-IR (VIRTIS) and submillimeter–millimeter (smm–mm, MIRO) wavelengths. Its primary mission is a 1 year reconnaissance of Comet 67P/Churyumov–Gerasimenko beginning in 2014. During a 2010 close fly-by of Asteroid 21 Lutetia, the VIRTIS and MIRO instruments provided complementary data that have been analyzed to produce a consistent model of Lutetia’s surface layer thermal and electrical properties, including a physical model of self-heating. VIRTIS dayside measurements provided highly resolved 1 K accuracy surface temperatures that required a low thermal inertia, I < 30 J/(K m2 s0.5). MIRO smm and mm measurements of polar night thermal fluxes produced constraints on Lutetia’s subsurface thermal properties to depths comparable to the seasonal thermal wave, yielding a model of I < 20 J/(K m2 s0.5) in the upper few centimeters, increasing with depth in a manner very similar to that of Earth’s Moon. Subsequent MIRO-based model predictions of the dayside surface temperatures reveal negative offsets of ～5–30 K from the higher VIRTIS-measurements. By adding surface roughness in the form of 50% fractional coverage of hemispherical mini-craters to the MIRO-based thermal model, sufficient self-heating is produced to largely remove the offsets relative to the VIRTIS measurements and also reproduce the thermal limb brightening features (relative to a smooth surface model) seen by VIRTIS. The Lutetia physical property constraints provided by the VIRTIS and MIRO data sets demonstrate the unique diagnostic capabilities of combined infrared and submillimeter/millimeter thermal flux measurements. 相似文献
5.
Franco Tassi Bruno Capaccioni Giorgio Caramanna Daniele Cinti Giordano Montegrossi Luca Pizzino Fedora Quattrocchi Orlando Vaselli 《Applied Geochemistry》2009
A geochemical survey of thermal waters collected from submarine vents at Panarea Island (Aeolian Islands, southern Italy) was carried out from December 2002 to March 2007, in order to investigate (i) the geochemical processes controlling the chemical composition of the hydrothermal fluids and (ii) the possible relations between the chemical features of the hydrothermal reservoir and the activity of the magmatic system. Compositional data of the thermal water samples were integrated in a hydrological conceptual model, which describes the formation of the vent fluid by mixing of seawater, seawater concentrated by boiling, and a deep, highly-saline end-member, whose composition is regulated by water-rock interactions at relatively high temperature and shows clear clues of magmatic-related inputs. The chemical composition of concentrated seawater was assumed to be represented by that of the water sample having the highest Mg content. The composition of the deep end-member was instead calculated by extrapolation assuming a zero-Mg end-member. The Na–K–Ca geothermometer, when applied to the thermal end-member composition, indicated an equilibrium temperature of approximately 300 °C, a temperature in agreement with the results obtained by gas-geothermometry. 相似文献
6.
Pinarelli Laura Gioncada Anna Capaccioni Bruno Vaselli Orlando Downes Hilary 《Mineralogy and Petrology》2019,113(1):39-60
Mineralogy and Petrology - Vulcano is part of the Aeolian volcanic arc in the southern Tyrrhenian Sea. Its products were emplaced through multiple episodes of edifice building and collapse since... 相似文献
7.
Computer-assisted Image Analysis can be succesfully used to derive quantitative information about grain-size distribution, particle shape and fabric on both consolidated and unconsolidated solid aggregates. We have developed a new analytical method that provides a series of quantitative textural parameters from whatever particulate deposits by combining commercial image acquisition system with devoted C-software. After exhaustive tests of the method, we applied it to a widespread Quaternary ignimbrite formation in central Italy (the Orvieto-Bagnoregio formation). The results suggest some new aspects of emplacement mechanisms of ignimbrites: (1) elongated particles shows variable degrees of flow-related preferred orientation both on horizontal and vertical planes; (2) vertical variations of flow-related preferred particle orientations follow a “zig-zag” pattern that we interpret to result from deposition by progressive aggradation during the passage of a particulate flow. The filling up of paleovalleys by means of progressive aggradation proceeds flank to flank due to alternating flow directions, induced by the already deposited material; (3) the occurrence of vertically spaced peaks on the strength of clast orientation suggests the existence of discrete depositional units deposited by aggradation from an unsteady but persisting flow. Strong fabrics are inferred to result from the high amount of shear stress imparted to particles at the depositional boundary layer, which at the same time can be responsible for the development of the basal inversely graded layer. Image analysis can also provide useful indications of paleoflow directions, paleotopographic details and ignimbrite source areas. 相似文献
8.
9.
F. Tosi R. Orosei A. Coradini G. Filacchione F. Capaccioni A. Adriani A. Negrão R.H. Brown M. Janssen J.W. Barnes R.N. Clark T.B. McCord J.M. Soderblom The Cassini VIMS RADAR Teams 《Icarus》2010,208(1):366-384
We apply a multivariate statistical method to Titan data acquired by different instruments onboard the Cassini spacecraft. We have searched through Cassini/VIMS hyperspectral cubes, selecting those data with convenient viewing geometry and that overlap with Cassini/RADAR scatterometry footprints with a comparable spatial resolution. We look for correlations between the infrared and microwave ranges the two instruments cover. Where found, the normalized backscatter cross-section obtained from the scatterometer measurement, corrected for incidence angle, and the calibrated antenna temperature measured along with the scatterometry echoes, are combined with the infrared reflectances, with estimated errors, to produce an aggregate data set, that we process using a multivariate classification method to identify homogeneous taxonomic units in the multivariate space of the samples.In medium resolution data (from 20 to 100 km/pixel), sampling relatively large portions of the satellite’s surface, we find regional geophysical units matching both the major dark and bright features seen in the optical mosaic. Given the VIMS cubes and RADAR scatterometer passes considered in this work, the largest homogeneous type is associated with the dark equatorial basins, showing similar characteristics as each other on the basis of all the considered parameters.On the other hand, the major bright features seen in these data generally do not show the same characteristics as each other. Xanadu, the largest continental feature, is as bright as the other equatorial bright features, while showing the highest backscattering coefficient of the entire satellite. Tsegihi is very bright at 5 μm but it shows a low backscattering coefficient, so it could have a low roughness on a regional scale and/or a different composition. Another well-defined region, located southwest of Xanadu beyond the Tui Regio, seems to be detached from the surrounding terrains, being bright at 2.69, 2.78 and 5 μm but having a low radar brightness. In this way, other units can be found that show correlations or anti-correlations between the scatterometric response and the spectrophotometric behavior, not evident from the optical remote sensing data. 相似文献
10.
Eleonora Ammannito M. Cristina De Sanctis Fabrizio Capaccioni M. Teresa Capria F. Carraro Jean‐Philippe Combe Sergio Fonte Alessandro Frigeri Steven P. Joy Andrea Longobardo Gianfranco Magni Simone Marchi Thomas B. McCord Lucy A. McFadden Harry Y. McSween Ernesto Palomba Carle M. Pieters Carol A. Polanskey Carol A. Raymond Jessica M. Sunshine Federico Tosi Francesca Zambon Christopher T. Russell 《Meteoritics & planetary science》2013,48(11):2185-2198
We present global lithological maps of the Vestan surface based on Dawn mission's Visible InfraRed (VIR) Spectrometer acquisitions with a spatial sampling of 200 m. The maps confirm the results obtained with the data set acquired by VIR with a spatial sampling of 700 m, that the reflectance spectra of Vesta's surface are dominated by pyroxene absorptions that can be interpreted within the context of the distribution of howardites, eucrites, and diogenites (HEDs). The maps also partially agree with the ground and Hubble Space Telescope observations: they confirm the background surface being an assemblage of howardite or polymict eucrite, as well as the location of a diogenitic‐rich spot; however, there is no evidence of extended olivine‐rich regions in the equatorial latitudes. Diogenite is revealed on the Rheasilvia basin floor, indicating that material of the lower crust/mantle was exposed. VIR also detected diogenites along the scarp of Matronalia Rupes, and the rims of Severina and a nearby, unnamed crater, and as ejecta of Antonia crater. The diogenite distribution is fully consistent with petrological constraints; although the mapped distribution does not provide unambiguous constraints, it favors the hypothesis of a magma ocean. 相似文献