共查询到20条相似文献，搜索用时 15 毫秒
1.
Adler I Trombka J Gerard J Lowman P Schmadebeck R Blodget H Eller E Yin L Lamothe R Gorenstein P Bjorkholm P 《Science (New York, N.Y.)》1972,175(4020):436-440
Although only part of the information from the x-ray fluorescence geochemical experiment has been analyzed, it is clear that the experiment was highly successful. Significant compositional differences among and possibly within the maria and highlands have been detected. When viewed in the light of analyzed lunar rocks and soil samples, and the data from other lunar orbital experiments (in particular, the Apollo 15 gamma-ray spectroscopy experiment), the results indicate the existence of a differential lunar highland crust, probably feldspathic. This crust appears to be related to the plagioclase-rich materials previously found in the samples from Apollo 11, Apollo 12, Apollo 14, Apollo 15, and Luna 16. 相似文献
2.
Feldman WC Boynton WV Tokar RL Prettyman TH Gasnault O Squyres SW Elphic RC Lawrence DJ Lawson SL Maurice S McKinney GW Moore KR Reedy RC 《Science (New York, N.Y.)》2002,297(5578):75-78
Global distributions of thermal, epithermal, and fast neutron fluxes have been mapped during late southern summer/northern winter using the Mars Odyssey Neutron Spectrometer. These fluxes are selectively sensitive to the vertical and lateral spatial distributions of H and CO2 in the uppermost meter of the martian surface. Poleward of +/-60 degrees latitude is terrain rich in hydrogen, probably H2O ice buried beneath tens of centimeter-thick hydrogen-poor soil. The central portion of the north polar cap is covered by a thick CO2 layer, as is the residual south polar cap. Portions of the low to middle latitudes indicate subsurface deposits of chemically and/or physically bound H2O and/or OH. 相似文献
3.
Reflectivity and polarization laws for the powder sample and its spectrum are close to the mean for the lunar maria. Solid samples show a marked absorption feature at 1 micron. The low albedo appears to be due to a surface coating on dust grains rather than to volume absorption. The high-frequency electrical properties resemble those of a fine powder made from typical dense terrestrial rocks and are consistent with previous estimates from ground-based radar observations. The differential mass spectrum is almost constant from 100 micron particles down to 0.1 micron particles; most particles are smaller than 0.3 micron. Their shapes disclose a variety of processes of generation. 相似文献
4.
Four experiments on lunar materials are reported: (i) resonance on glass spheres from the soil; (ii) compressibility of rock 10017; (iii) sound velocities of rocks 10046 and 10017; (iv) sound velocity of the lunar fines. The data overlap and are mutually consistent. The glass beads and rock 10017 have mechanical properties which correspond to terrestrial materials. Results of (iv) are consistent with low seismic travel times in the lunar maria. Results of analysis of the microbreccia (10046) agreed with the soil during the first pressure cycle, but after overpressure the rock changed, and it then resembled rock 10017. Three models of the lunar surface were constructed giving density and velocity profiles. 相似文献
5.
Wänke H Begemann F Vilcsek E Rieder R Teschke F Born W Quijano-Rico M Voshage H Wlotzka F 《Science (New York, N.Y.)》1970,167(3918):523-525
Analytical data for 42 major and trace elements were mostly obtained by a combination of instrumental and radiochemical neutron activation analyses using both thermal and 14-million-electronvolt neutrons. Excesses of nitrogen and chlorine in the fines, compared with the rocks, are attributed to the solar wind. A striking similarity for contents of seven elements in lunar metal and metal from the calcium-rich achondrite Juvinas was noted. Fractional dissolution was used to separate five radionuclides produced by cosmic-ray bombardment in the fines and rock 57-40. Results for argon-39 from the reaction potassium-39 (n,p), and for argon-37, from the reaction calcium-40 (n,a), seem to require a neutron spectrum conitaining more neutrons below 2 million electronvolts than the evaporation spectrum or that given by Arnold, Honda, and Lal (1) or a strong time dependence for the neutron flux. 相似文献
6.
Rubidium-strontium age and elemental and isotopic abundances of some trace elements in lunar samples
Data on six lunar crystalline rocks give an apparent Rb-Sr isochron age of 4.42 +/- 0.24 x 10(9) years (95 percent confidence limits) and initial (87)Sr/(86)Sr ratio similar to that in a basaltic achondrite. Relationships between K, Rb, Sr, and Ba and depletion of Eu in these samples point to plagioclase separation from the melts that produced these rocks. The abundance of (157)Gd in the three lunar samples is similar to terrestrial abundance within < 0.2 percent, thus setting a limit of < 6 x 10(15) neutrons per square centimeter for the integrated thermal neutron flux difference between lunar and terrestrial materials. 相似文献
7.
Baird AK Toulmin P Clark BC Rose HJ Keil K Christian RP Gooding JL 《Science (New York, N.Y.)》1976,194(4271):1288-1293
Chemical results from four samples of martian fines delivered to Viking landers 1 and 2 are remarkably similar in that they all have high iron; moderate magnesium, calcium, and sulfur; low aluminum; and apparently very low alkalies and trace elements. This composition is best interpreted as representing the weathering products of mafic igneous rocks. A mineralogic model, derived from computer mixing studies and laboratory analog preparations, suggests that Mars fines could be an intimate mixture of about 80 percent iron-rich clay, about 10 percent magnesium sulfate (kieserite?), about 5 percent carbonate (calcite), and about 5 percent iron oxides (hematite, magnetite, maghemite, goethite?). The mafic nature of the present fines (distributed globally) and their probable source rocks seems to preclude large-scale planetary differentiation of a terrestrial nature. 相似文献
8.
Pieters CM 《Science (New York, N.Y.)》1982,215(4528):59-61
Olivine is identified as the major mafic mineral in a central peak of Copernicus crater. Information on the mineral assemblages of such unsampled lunar surface material is provided by near infrared reflectance spectra (0.7 to 2.5 micrometers) obtained with Earth-based telescopes. The composition of the deep-seated material comprising the Copernicus central peak is unique among measured areas. Other lunar terra areas and the wall of Copernicus exhibit spectral characteristics of mineral assemblages comparable to the feldspathic breccias returned by the Apollo missions, with low-calcium orthopyroxene being the major mafic mineral. 相似文献
9.
Crystalline rocks from Mare Tranquillitatis have yielded potassium-argon dates as old as 3.8 x 10(9) years. Crystalline rocks from Oceanus Procellarum give potassium-argon ages as old as 2.8 x 10(9) years. Evidently the maria are ancient features of the moon and were not formed contemporaneously, a conclusion that also has been verified by other methods. The potassium-argon ages of rocks from Oceanus Procellarum show much more loss of argon than the rocks from Mare Tranquillitatis, an indication that the rocks at Oceanus Procellarum have experienced more severe shock effects or longer cooling rates. 相似文献
10.
Apollo Preliminary Examination Team 《Science (New York, N.Y.)》1972,175(4020):363-375
Samples returned from the Apollo 15 site consist of mare basalts and breccias with a variety of premare igneous rocks. The mare basalts are from at least two different lava flows. The bulk chemical compositions and textures of these rocks confirm the previous conclusion that the lunar maria consist of a series of extrusive volcanic rocks that are rich in iron and poor in sodium. The breccias contain abundant clasts of anorthositic fragments along with clasts of basaltic rocks much richer in plagioclase than the mare basalts. These two rock types also occur as common components in soil samples from this site. The rocks and soils from both the front and mare region exhibit a variety of shock characteristics that can best be ascribed to ray material from the craters Aristillus or Autolycus. 相似文献
11.
At a confining pressure of a few kilobars, deformation of many sedimentary rocks, altered mafic rocks, porous volcanic rocks, and sand is ductile, in that instabilities leading to audible elastic shocks are absent. At pressures of 7 to 10 kilobars, however, unstable faulting and stick-slip in certain of these rocks was observed. This high pressure-low temperature instability might be responsible for earthquakes in deeply buried sedimentary or volcanic sequences. 相似文献
12.
Fortescue P 《Science (New York, N.Y.)》1977,196(4296):1326-1329
Expressions are developed to allow ready comparison of a hybrid fission-fusion plant and a fast breeder with respect to the number of thermal reactors that their fissile production could support, both for their feed requirements and for the new inventory needs of an expanding industry. These relations are expressed in terms of the neutron multiplication factor obtained in the fusion blanket, and the analogous quantities represented by the conversion ratios of the fast and thermal fission associated with the comparison. Results are presented graphically both for the steady state and for industries of arbitrary growth rate, and include the influence of tritium production requirements. Even a modest blanket neutron multiplication factor could enable the hybrid fusion system greatly to outperform the fast breeder on this simple basis of material balances. 相似文献
13.
利用青藏高原玛多草句和玉树隆宝湿地的观测资料,比较分析了2种不同下垫面的净辐射通量、感热通量、潜热通量、土壤湿度和地表反照率的逐月日变化特征,并计算了2个地区各月地表反照率。结果表明,玛多草句和玉树隆宝湿地净辐射通量夏秋季高、冬春季低。夏季,草句下垫面感热通量日变化高于湿地下垫面;冬季,草甸和湿地2种下垫面的感热通量日变化相差不大;2种下垫面潜热通量均为夏季高、冬季低。各月湿地下垫面潜热通量高于草句下垫面,各月份湿地下垫面土壤湿度高于草甸下垫面;在一年当中,湿地下垫面10cm深处土壤湿度变化幅度很大,草甸下垫面10cm深处土壤湿度在一年当中变化幅度很小。2种下垫面地表反照率冬季高、夏李低,草甸和湿地2种下垫面年平均地表反照率分别为0．27和0．25。 相似文献
14.
Basu AR Poreda RJ Renne PR Teichmann F Vasiliev YR Sobolev NV Turrin BD 《Science (New York, N.Y.)》1995,269(5225):822-825
An olivine nephelinite from the lower part of a thick alkalic ultrabasic and mafic sequence of volcanic rocks of the northeastern part of the Siberian flood basalt province (SFBP) yielded a (40)Ar/(39)Ar plateau age of 253.3 +/- 2.6 million years, distinctly older than the main tholeiitic pulse of the SFBP at 250.0 million years. Olivine phenocrysts of this rock showed (3)He/(4)He ratios up to 12.7 times the atmospheric ratio; these values suggest a lower mantle plume origin. The neodymium and strontium isotopes, rare earth element concentration patterns, and cerium/lead ratios of the associated rocks were also consistent with their derivation from a near-chondritic, primitive plume. Geochemical data from the 250-million-year-old volcanic rocks higher up in the sequence indicate interaction of this high-(3)He SFBP plume with a suboceanic-type upper mantle beneath Siberia. 相似文献
15.
The 1994 eruption of Rabaul, in Papua New Guinea, involved a small plinian eruption at Vulcan and a vulcanian eruption on the opposite side of the caldera at Tavurvur. Vulcan's ash leachates indicate seawater interaction that is consistent with earlier observations of low sulfur dioxide emissions and the presence of ice crystals in the initial plinian eruption cloud. In contrast, Tavurvur ash leachates indicate no seawater interaction, and later sulfur dioxide emissions remained high despite low-level eruptive activity. Silicic melt inclusions indicate that the andesitic melt contained about 2 weight percent water and negligible carbon dioxide. Mafic melt inclusions in Tavurvur ash have water and carbon dioxide contents that vary systematically over the course of the eruption. The mafic melt inclusions suggest that a mafic dike intruded from below the silicic chamber and provide further evidence that mafic intrusions drive caldera unrest. 相似文献
16.
Hot and dry deep crustal xenoliths from tibet 总被引：8，自引：0，他引：8
Hacker BR Gnos E Ratschbacher L Grove M McWilliams M Sobolev SV Wan J Zhenhan W 《Science (New York, N.Y.)》2000,287(5462):2463-2466
Anhydrous metasedimentary and mafic xenoliths entrained in 3-million-year-old shoshonitic lavas of the central Tibetan Plateau record a thermal gradient reaching about 800 degrees to 1000 degrees C at a depth of 30 to 50 kilometers; just before extraction, these same xenoliths were heated as much as 200 degrees C. Although these rocks show that the central Tibetan crust is hot enough to cause even dehydration melting of mica, the absence of hydrous minerals, and the match of our calculated P-wave speeds and Poisson's ratios with seismological observations, argue against the presence of widespread crustal melting. 相似文献
17.
Ratcliff CD Geissman JW Perry FV Crowe BM Zeitler PK 《Science (New York, N.Y.)》1994,266(5184):412-416
Late Miocene (about 8.65 million years ago) mafic intrusions and lava flows along with remagnetized host rocks from Paiute Ridge, southern Nevada, provide a high-quality paleomagnetic record of a geomagnetic field reversal. These rocks yield thermoremanent magnetizations with declinations of 227 degrees to 310 degrees and inclinations of -7 degrees to 49 degrees , defining a reasonably continuous virtual geomagnetic pole path over west-central Pacific longitudes. Conductive cooling estimates for the intrusions suggest that this field transition, and mafic magmatism, lasted only a few hundred years. Because this record comes principally from intrusive rocks, rather than sediments or lavas, it is important in demonstrating the longitudinal confinement of the geomagnetic field during a reversal. 相似文献
18.
Bebout GE 《Science (New York, N.Y.)》1991,251(4992):413-416
Metamorphic rocks on Santa Catalina Island, California, afford examination of fluid-related processes at depths of 15 to 45 kilometers in an Early Cretaceous subduction zone. A combination of field, stable isotope, and volatile content data for the Catalina Schist indicates kilometer-scale transport of large amounts of water-rich fluid with uniform oxygen and hydrogen isotope compositions. The fluids were liberated in devolatilizing, relatively low-temperature (400 degrees to 600 degrees C) parts of the subduction zone, primarily by chlorite-breakdown reactions. An evaluation of pertinent phase equilibria indicates that chlorite in mafic and sedimentary rocks and melange may stabilize a large volatile component to great depths (perhaps >100 kilometers), depending on the thermal structure of the subduction zone. This evidence for deep volatile subduction and large-scale flow of slab-derived, water-rich fluids lends credence to models that invoke fluid addition to sites of arc magma genesis. 相似文献
19.
Bell JF Squyres SW Arvidson RE Arneson HM Bass D Calvin W Farrand WH Goetz W Golombek M Greeley R Grotzinger J Guinness E Hayes AG Hubbard MY Herkenhoff KE Johnson MJ Johnson JR Joseph J Kinch KM Lemmon MT Li R Madsen MB Maki JN Malin M McCartney E McLennan S McSween HY Ming DW Morris RV Dobrea EZ Parker TJ Proton J Rice JW Seelos F Soderblom JM Soderblom LA Sohl-Dickstein JN Sullivan RJ Weitz CM Wolff MJ 《Science (New York, N.Y.)》2004,306(5702):1703-1709
Panoramic Camera (Pancam) images from Meridiani Planum reveal a low-albedo, generally flat, and relatively rock-free surface. Within and around impact craters and fractures, laminated outcrop rocks with higher albedo are observed. Fine-grained materials include dark sand, bright ferric iron-rich dust, angular rock clasts, and millimeter-size spheroidal granules that are eroding out of the laminated rocks. Spectra of sand, clasts, and one dark plains rock are consistent with mafic silicates such as pyroxene and olivine. Spectra of both the spherules and the laminated outcrop materials indicate the presence of crystalline ferric oxides or oxyhydroxides. Atmospheric observations show a steady decline in dust opacity during the mission. Astronomical observations captured solar transits by Phobos and Deimos and time-lapse observations of sunsets. 相似文献
20.
黔中喀斯特地区不同岩性土壤的抗蚀抗冲性研究 总被引：2，自引：0，他引：2
对贵州省中部喀斯特地区4种典型成土母岩(灰质白云岩,石灰岩,长石石英砂岩,白云岩)发育的土壤的抗蚀抗冲性进行研究。结果表明:可将衡量土壤抗蚀性的12个指标压缩为3个最佳指标。抗蚀性指标主成分分析综合指数表明,4种岩性土壤抗蚀性为:灰质白云岩(43.42)>石灰岩(5.49)>白云岩(2.72)>长石石英砂岩(-34.49);15°、20°、30°3个坡度下的抗冲性显著不同,随着坡度的增加,4种岩性土壤抗冲性显著差异也逐渐增加;4种岩性土壤抗冲性变化规律与抗蚀性吻合,土壤抗冲性强弱与抗蚀性强弱趋于一致。土壤的抗蚀性与抗冲性与成土母岩的性质关系密切。 相似文献