共查询到20条相似文献，搜索用时 62 毫秒
1.
McClintock WE Izenberg NR Holsclaw GM Blewett DT Domingue DL Head JW Helbert J McCoy TJ Murchie SL Robinson MS Solomon SC Sprague AL Vilas F 《Science (New York, N.Y.)》2008,321(5885):62-65
During MESSENGER's first flyby of Mercury, the Mercury Atmospheric and Surface Composition Spectrometer made simultaneous mid-ultraviolet to near-infrared (wavelengths of 200 to 1300 nanometers) reflectance observations of the surface. An ultraviolet absorption (<280 nanometers) suggests that the ferrous oxide (Fe2+) content of silicates in average surface material is low (less than 2 to 3 weight percent). This result is supported by the lack of a detectable 1-micrometer Fe2+ absorption band in high-spatial-resolution spectra of mature surface materials as well as immature crater ejecta, which suggests that the ferrous iron content may be low both on the surface and at depth. Differences in absorption features and slope among the spectra are evidence for variations in composition and regolith maturation of Mercury's surface. 相似文献
2.
廖宗文 《华南农业大学学报》1993,14(3):1-5
以土袋水培法,结合普通盆栽研究水稻黄叶生理病与红壤溶液Fe、Si关系果表明,与无稻红壤溶液相比,植稻红壤的Si/Fe下降而土袋水培Si/Fe升高。电子探针分析显示土培稻根表皮层细胞外壁的Fe峰很高,而土袋水培者的Fe峰很低或为零。讨论了土袋水培的Si/Fe升高的原因及其对消除水稻黄叶生理病的作用。 相似文献
3.
The spectrum of Mercury at the Fraunhofer sodium D lines shows strong emission features that are attributed to resonant scattering of sunlight from sodium vapor in the atmosphere of the planet. The total column abundance of sodium was estimated to be 8.1 x 10(11) atoms per square centimeter, which corresponds to a surface density at the subsolar point of about 1.5 x 10(5) atoms per cubic centimeter. The most abundant atmospheric species found by the Mariner 10 mission to Mercury was helium, with a surface density of 4.5 x 10(3) atoms per cubic centimeter. It now appears that sodium vapor is a major constituent of Mercury's atmosphere. 相似文献
4.
Analysis of data obtained by the ultraviolet experiment on Mariner 10 indicates that Mercury is surrounded by a thin atmosphere consisting in part of helium. The partial pressure of helium at the terminator is about 5 x 10(-12) millibar. The total surface pressure of the atmosphere is less than about 2 x 10(-9) millibar. Upper limits are set for the abundance of various gases, including hydrogen, oxygen, carbon, argon, neon, and xenon. The wavelength dependence of Mercury's surface albedo is similar to that of the moon over a broad range of wavelengths from 500 to 1600 angstroms. Strong signals were recorded by the airglow instrument as Mariner 10 passed through the cavity behind Mercury. They are as yet unexplained but may provide information on the properties of the local plasma. 相似文献
5.
Solomon SC McNutt RL Watters TR Lawrence DJ Feldman WC Head JW Krimigis SM Murchie SL Phillips RJ Slavin JA Zuber MT 《Science (New York, N.Y.)》2008,321(5885):59-62
In January 2008, the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft became the first probe to fly past the planet Mercury in 33 years. The encounter revealed that Mercury is a dynamic system; its liquid iron-rich outer core is coupled through a dominantly dipolar magnetic field to the surface, exosphere, and magnetosphere, all of which interact with the solar wind. MESSENGER images confirm that lobate scarps are the dominant tectonic landform and record global contraction associated with cooling of the planet. The history of contraction can be related to the history of volcanism and cratering, and the total contractional strain is at least one-third greater than inferred from Mariner 10 images. On the basis of measurements of thermal neutrons made during the flyby, the average abundance of iron in Mercury's surface material is less than 6% by weight. 相似文献
6.
Iron, calcium, aluminum, silicon, and sulfur are major elements in the first surface sample of Mars that has been analyzed by the Viking x-ray fluorescence spectrometer. Titanium is present in minor quantities. This is consistent with the sample being a mixture of fine silicate and oxide mineral grains, with a significant proportion of sulfates, possibly hydrated. Ferric oxide is regarded as the red pigmenting agent on the martian surface, but if it coats silicate grains, the coatings must be very thin (相似文献
7.
为探讨硅铁施用对水稻生长和磷吸收的影响,指导合理施肥、提高磷素利用率,利用水培试验研究了不同浓度铁（0、0.5、1、2 mmol·L-1）预处理下施加不同浓度硅（0、1、4 mmol·L-1）对水稻生长及磷吸收的影响。结果表明,低浓度的铁预处理对水稻SPAD、株高、根长和地上部干质量无显著影响,而高浓度的铁预处理下,这些指标则显著降低（P<0.05）。中低浓度铁处理下施硅在一定程度上增加了水稻株高、根长和地上部干质量,但未达到显著水平（P>0.05）。铁预处理显著增加了水稻根表铁膜的厚度及根表铁膜中的磷含量（P<0.05）,施硅则显著降低了0.5 mmol·L-1和1 mmol·L-1铁预处理的水稻根表铁膜的厚度（P<0.05）。铁预处理对水稻根部的磷含量无显著影响,但显著降低了地上部磷的含量（P<0.05）。施硅对水稻根和地上部的磷含量无显著影响。研究表明,施铁处理显著诱导了根表铁膜的出现,增加了铁膜中的磷含量并且显著降低了地上部的磷含量;施硅在一定程度上缓解了水稻生长中的铁毒害现象,并且能够改变根表铁膜厚度,减少根冠比,从而影响水稻磷的吸收转运。 相似文献
8.
Recalibration of Mariner 10 color image data allows the identification of distinct color units on the mercurian surface. We analyze these data in terms of opaque mineral abundance, iron content, and soil maturity and find color units consistent with the presence of volcanic deposits on Mercury's surface. Additionally, materials associated with some impact craters have been excavated from a layer interpreted to be deficient in opaque minerals within the crust, possibly analogous to the lunar anorthosite crust. These observations suggest that Mercury has undergone complex differentiation like the other terrestrial planets and the Earth's moon. 相似文献
9.
在小兴凯湖采集水样,滤掉浮游动物,对浮游植物进行为期12 d的实验室培养。试验设置了4个光照梯度和5个Fe浓度,分别进行对比试验。结果表明：随着Fe浓度的增加,浮游植物对Fe的吸收量也相应的增加。在低光照强度下,浮游植物对Fe的吸收规律不明显。在光强为4000 lx时,浮游植物吸收Fe量为0的培养瓶中浮游植物丰度降低了63．6 ind· L－1。在光强为8000 lx条件下,浮游植物丰度与吸收Fe量呈正相关关系。在光强为12000 lx时,吸收Fe量为0．091 mg· L－1的培养瓶中浮游植物丰度增加了2791．2 ind· L－1,说明了光照强度对藻类生长的限制作用明显高于培养液中营养元素对藻类生长的限制作用。 相似文献
10.
水稻黄叶生理病与硅肥施用效果 总被引：2，自引：0，他引：2
新垦红壤植稻后发生的黄叶生理病与铁毒缺硅有关。施用硅肥能提高土壤有效硅含量,并提高土壤水溶性及活性Si/Fe值,抑制黄叶生理病症,改善水稻生长状况,提高水稻产量。电子探针分析根内元素表明:施用硅肥可减少铁在根表皮层的积累,增加根内皮层硅钙的含量。 相似文献
11.
Zurbuchen TH Raines JM Gloeckler G Krimigis SM Slavin JA Koehn PL Killen RM Sprague AL McNutt RL Solomon SC 《Science (New York, N.Y.)》2008,321(5885):90-92
The region around Mercury is filled with ions that originate from interactions of the solar wind with Mercury's space environment and through ionization of its exosphere. The MESSENGER spacecraft's observations of Mercury's ionized exosphere during its first flyby yielded Na+, O+, and K+ abundances, consistent with expectations from observations of neutral species. There are increases in ions at a mass per charge (m/q) = 32 to 35, which we interpret to be S+ and H2S+, with (S+ + H2S+)/(Na+ + Mg+) = 0.67 +/- 0.06, and from water-group ions around m/q = 18, at an abundance of 0.20 +/- 0.03 relative to Na+ plus Mg+. The fluxes of Na+, O+, and heavier ions are largest near the planet, but these Mercury-derived ions fill the magnetosphere. Doubly ionized ions originating from Mercury imply that electrons with energies less than 1 kiloelectron volt are substantially energized in Mercury's magnetosphere. 相似文献
12.
Bishop JL Dobrea EZ McKeown NK Parente M Ehlmann BL Michalski JR Milliken RE Poulet F Swayze GA Mustard JF Murchie SL Bibring JP 《Science (New York, N.Y.)》2008,321(5890):830-833
Observations by the Mars Reconnaissance Orbiter/Compact Reconnaissance Imaging Spectrometer for Mars in the Mawrth Vallis region show several phyllosilicate species, indicating a wide range of past aqueous activity. Iron/magnesium (Fe/Mg)-smectite is observed in light-toned outcrops that probably formed via aqueous alteration of basalt of the ancient cratered terrain. This unit is overlain by rocks rich in hydrated silica, montmorillonite, and kaolinite that may have formed via subsequent leaching of Fe and Mg through extended aqueous events or a change in aqueous chemistry. A spectral feature attributed to an Fe2+ phase is present in many locations in the Mawrth Vallis region at the transition from Fe/Mg-smectite to aluminum/silicon (Al/Si)-rich units. Fe2+-bearing materials in terrestrial sediments are typically associated with microorganisms or changes in pH or cations and could be explained here by hydrothermal activity. The stratigraphy of Fe/Mg-smectite overlain by a ferrous phase, hydrated silica, and then Al-phyllosilicates implies a complex aqueous history. 相似文献
13.
采用振荡培养实验研究了纳米Fe0对溶液中3,3′,4,4′-四氯联苯（PCB77）的降解情况,结果表明, PCB77起始浓度为5mg/L、溶液初始pH值为6.8,反应64 h后,纳米Fe0投加量为10.0g/L时,PCB77残留浓度最低,残留率仅为29.3%;纳米Si0投加量为0.5g/L时,PCB77残留浓度最低,残留率为67%;纳米Si0投加量为1.0g/L,即纳米Si0：纳米Fe0=1∶10时,PCB77残留浓度最低,残留率仅为22.2%。溶液中PCB77降解产物中除联苯外未发现其他降解产物,可能是PCB77在纳米Fe0表面连续脱氯的原因造成的。 相似文献
14.
Isotopic analyses of nickel in samples from the differentiated meteorite Chervony Kut revealed the presence of relative excesses of (60)Ni ranging from 2.4 up to 50 parts per 10(4). These isotopic excesses are from the decay of the now extinct short-lived nuclide (60)Fe and provide clear evidence for the existence of (60)Fe over large scales in the early solar system. Not only was (60)Fe present at the time of melting and differentiation (that is, Fe-Ni fractionation) of the parent body of Chervony Kut but also later at the time when basaltic magma solidified at or near the surface of the planetesimal. The inferred abundance of (60)Fe suggests that its decay alone could have provided sufficient heat to melt small (diameters of several hundred kilometers) planetary bodies shortly after their accretion. 相似文献
15.
Peplowski PN Evans LG Hauck SA McCoy TJ Boynton WV Gillis-Davis JJ Ebel DS Goldsten JO Hamara DK Lawrence DJ McNutt RL Nittler LR Solomon SC Rhodes EA Sprague AL Starr RD Stockstill-Cahill KR 《Science (New York, N.Y.)》2011,333(6051):1850-1852
The MESSENGER Gamma-Ray Spectrometer measured the average surface abundances of the radioactive elements potassium (K, 1150 ± 220 parts per million), thorium (Th, 220 ± 60 parts per billion), and uranium (U, 90 ± 20 parts per billion) in Mercury's northern hemisphere. The abundance of the moderately volatile element K, relative to Th and U, is inconsistent with physical models for the formation of Mercury requiring extreme heating of the planet or its precursor materials, and supports formation from volatile-containing material comparable to chondritic meteorites. Abundances of K, Th, and U indicate that internal heat production has declined substantially since Mercury's formation, consistent with widespread volcanism shortly after the end of late heavy bombardment 3.8 billion years ago and limited, isolated volcanic activity since. 相似文献
16.
采用培养试验方法研究了硅肥对酸性土壤中锰毒性的影响,旨在为酸性土壤锰毒害的防控提供科学依据.结果表明,甘蔗的根际效应明显,根际土壤中的pH值、有效硅含量较低而活性锰及水溶态锰、交换态锰、有机结合态锰、碳酸盐结合态锰、铁锰氧化态锰含量均显著高于土体.然而,施用硅肥(偏硅酸钠)后,土壤活性锰含量和水溶态、交换态、有机结合态锰含量均显著降低,但是硅肥对根际土壤锰含量和形态的效应弱于土体;并且,施用硅肥使甘蔗地上部锰含量(47.1～112.1 mg/kg)显著降低,并且有随着硅肥用量(0.5～2.1 g/kg)增加而降低的趋势;虽然硅肥的施用也减少甘蔗地上部铁的含量,但铁锰比值却从对照的2.51增加至2.92～5.72之间.因此,施用硅肥后甘蔗株高、总生物量分别提高4.07％～15.24％、8.41％～28.03％.可见,硅肥的施用减轻了酸性土壤中锰的毒害. 相似文献
17.
采用培养试验方法研究了硅肥对酸性土壤中锰毒性的影响, 旨在为酸性土壤锰毒害的防控提供科学依据。结果表明,甘蔗的根际效应明显, 根际土壤中的pH值、有效硅含量较低而活性锰及水溶态锰、交换态锰、有机结合态锰、碳酸盐结合态锰、铁锰氧化态锰含量均显著高于土体。然而,施用硅肥(偏硅酸钠)后,土壤活性锰含量和水溶态、交换态尧、机结合态锰含量均显著降低, 但是硅肥对根际土壤锰含量和形态的效应弱于土体;并且,施用硅肥使甘蔗地上部锰含量(47.1~112.1 mg/kg)显著降低, 并且有随着硅肥用量(0.5~2.1 g/kg)增加而降低的趋势;虽然硅肥的施用也减少甘蔗地上部铁的含量, 但铁锰比值却从对照的2.51 增加至2.92~5.72 之间。因此,施用硅肥后甘蔗株高、总生物量分别提高4.07%~15.24%、8.41%~28.03%。可见, 硅肥的施用减轻了酸性土壤中锰的毒害。 相似文献
18.
本文应用x射线能谱技术，对获能前后精子质膜表面（头部、中段）和内部（顶体内、中段线粒体内）的元素进行了分析测试。结果表明，牛精子用肝素+咖啡因体外获能后，头部、中段质膜表面的Na、Al、S、K含量升高，Cl、Ca含量降低；顶体内Na、Mg、Si、P和Fe含量降低，而Ca、K、Cl和S含量升高；精子中段线粒体内Na、P、Si、Cl和Ca升高，而Mg、S、K和Fe却降低。获能过程中精子顶体内Na/Ca、Na/K、Cl/Ca、Cl/K和Na/Cl的浓度比分别为42.13、12.43、15.36、45.31和2.74；而摩尔比又分别为73.42、21.13、17.37、4.99和4.23。本文并对可能的获能机理进行了讨论。 相似文献
19.
冯立孝 《西北农林科技大学学报(自然科学版)》1990,(4):69-73
对黄棕壤和黄褐土的诊断特征进行了比较研究,结果表明,黄棕壤在酸性淋溶条件下,已处于初期富铝化阶段,呈酸性反应,代换酸、水解酸和活性铝含量较高,盐基不饱和,粘粒硅铁铝率和硅铝率较小,粘土矿物以(石至)石为主。黄褐土因受含钙粘黄土母质的影响,阻滞和延缓了富铝化过程,呈弱酸至弱碱反应,代换酸、水解酸与活性铝含量甚微,盐基饱和或基本饱和,粘粒硅铁铝率和硅铝率较高,粘土矿物以水云母为主。成土过程和诊断特征的明显差别,表明黄棕壤、黄褐土应属两个土类。 相似文献
20.
Monochromatic images of Mercury at the sodium D(2) emission line showed excess sodium emission in localized regions at high northern and southern latitudes and day-to-day global variations in the distribution of sodium emission. These phenomena support the suggestion that magnetospheric effects could be the cause. Sputtering of surface minerals could produce sodium vapor in polar regions during magnetic substorms, when magnetospheric ions directly impact the surface. Another important process may be the transport of sodium ions along magnetic field lines toward polar regions, where they impact directly on the surface of Mercury and are neutralized to regenerate neutral sodium atoms. Day-to-day variations in planetary sodium distributions could result from changing solar activity, which can change the magnetosphere in time scales of a few hours. Observations of the sodium exosphere may provide a tool for remote monitoring of the magnetosphere of Mercury. 相似文献