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1.
An overview of the Voyager 2 encounter with Neptune is presented, including a brief discussion of the trajectory, the planned observations, and highlights of the results described in the 11 companion papers. Neptune's blue atmosphere has storm systems reminiscent of those in Jupiter's atmosphere. An optically thin methane ice cloud exists near the 1.5-bar pressure level, and an optically thick cloud exists below 3 bars. Neptune's magnetic field is highly tilted and offset from the planet's center; it rotates with a period of 16.11 hours. Two narrow and two broad rings circle the planet; the outermost of these rings has three optically thicker arc segments. Six new moons were discovered in circular prograde orbits, all well inside Triton's retrograde orbit. Triton has a highly reflective and geologically young surface, a thin nitrogen atmosphere, and at least two active geyser-like plumes. 相似文献
2.
Pioneer 11 has made the first exploration of the magnetosphere and trapped radiation belts of Saturn. Saturn's magnetosphere is intermediate in size between Earth's and Jupiter's, with trapped particle intensities comparable to Earth's. The outer region of Saturn's magnetosphere contains lower energy radiation and is variable with time; the inner region contains higher energy particles. The pitch angle distributions show a remarkable variety of field-aligned and locally mirroring configurations. The moons and especially the rings of Saturn are effective absorbers of trapped particles; underneath the rings, the trapped radiation is completely absorbed. We confirm the discovery of a new ring, called the F ring, a new division, the Pioneer division, and a moon, called 1979 S 2. The latter has probably been seen from Earth. There may be evidence for more bodies like 1979 S 2, but at this stage the interpretation of the data is ambiguous. Using particle diffusion rates, we estimate that the cross-sectional area of the F ring is > 7 x 10(13) square centimeters and that the opacity is > 10(-5). Cosmic-ray albedo neutron decay should be looked into as a source of energetic particles in the inner magnetosphere of Saturn. 相似文献
3.
In August 2009 the Sun illuminated Saturn's rings from almost exactly edge-on, revealing a subtle corrugation that extends across the entire C ring. This corrugation's amplitude is 2 to 20 meters and its wavelength is 30 to 80 kilometers. Radial trends in the corrugation's wavelength indicate that this structure--like a similar corrugation previously identified in the D ring--results from differential nodal regression within a ring that became tilted relative to Saturn's equator plane in 1983. We suggest that this initial tilt arose because interplanetary debris struck the rings. The corrugation's radial extent implies that the impacting material was a dispersed cloud of debris instead of a single object, and the corrugation's amplitude indicates that the debris' total mass was ~10(11) to 10(13) kilograms. 相似文献
4.
Esposito LW Colwell JE Larsen K McClintock WE Stewart AI Hallett JT Shemansky DE Ajello JM Hansen CJ Hendrix AR West RA Keller HU Korth A Pryor WR Reulke R Yung YL 《Science (New York, N.Y.)》2005,307(5713):1251-1255
Neutral oxygen in the saturnian system shows variability, and the total number of oxygen atoms peaks at 4 x 10(34). Saturn's aurora brightens in response to solar-wind forcing, and the auroral spectrum resembles Jupiter's. Phoebe's surface shows variable water-ice content, and the data indicate it originated in the outer solar system. Saturn's rings also show variable water abundance, with the purest ice in the outermost A ring. This radial variation is consistent with initially pure water ice bombarded by meteors, but smaller radial structures may indicate collisional transport and recent renewal events in the past 10(7) to 10(8) years. 相似文献
5.
Sandel BR Shemansky DE Broadfoot AL Holberg JB Smith GR McConnell JC Strobel DF Atreya SK Donahue TM Moos HW Hunten DM Pomphrey RB Linick S 《Science (New York, N.Y.)》1982,215(4532):548-553
Combined analysis of helium (584 angstroms) airglow and the atmospheric occultations of the star delta Scorpii imply a vertical mixing parameter in Saturn's upper atmosphere of K (eddy diffusion coefficient) approximately 8 x 10(7) square centimeters per second, an order of magnitude more vigorous than mixing in Jupiter's upper atmosphere. Atmospheric H(2) band absorption of starlight yields a preliminary temperature of 400 K in the exosphere and a temperature near the homopause of approximately 200 K. The energy source for the mid-latitude H(2) band emission still remains a puzzle. Certain auroral emissions can be fully explained in terms of electron impact on H(2), and auroral morphology suggests a link between the aurora and the Saturn kilometric radiation. Absolute optical depths have been determined for the entire C ring andparts of the A and B rings. A new eccentric ringlet has been detected in the C ring. The extreme ultraviolet reflectance of the rings is fairly uniform at 3.5 to 5 percent. Collisions may control the distribution of H in Titan's H torus, which has a total vertical extent of approximately 14 Saturn radii normal to the orbit plane. 相似文献
6.
Smith BA Soderblom LA Beebe R Boyce J Briggs G Carr M Collins SA Cook AF Danielson GE Davies ME Hunt GE Ingersoll A Johnson TV Masursky H McCauley J Morrison D Owen T Sagan C Shoemaker EM Strom R Suomi VE Veverka J 《Science (New York, N.Y.)》1979,206(4421):927-950
Voyager 2, during its encounter with the Jupiter system, provided images that both complement and supplement in important ways the Voyager 1 images. While many changes have been observed in Jupiter's visual appearance, few, yet significant, changes have been detected in the principal atmospheric currents. Jupiter's ring system is strongly forward scattering at visual wavelengths and consists of a narrow annulus of highest particle density, within which is a broader region in which the density is lower. On Io, changes are observed in eruptive activity, plume structure, and surface albedo patterns. Europa's surface retains little or no record of intense meteorite bombardment, but does reveal a complex and, as yet, little-understood system of overlapping bright and dark linear features. Ganymede is found to have at least one unit of heavily cratered terrain on a surface that otherwise suggests widespread tectonism. Except for two large ringed basins, Callisto's entire surface is heavily cratered. 相似文献
7.
长白落叶松水分输导模式及叶生物量估测方法 总被引：1，自引：0，他引：1
根据管道模型理论，以年轮为基本研究单位，利用生物染色剂染色试验对长白落叶松的水分输导模式进行研究发现：长白落叶松不同年轮的水分纵向输导能力差异很大；以最近3年生长的年轮输导能力最强，年轮间水分横向输导现象不明显。纵向输导在同一年轮内呈明显的管道状输导。依据胸高处最近5个年轮的横断面积建立了长白落叶松叶生物量估测模型，复相关系数达到了0.97。 相似文献
8.
The most prominent oscillatory feature observed in the Voyager 1 radio occultation of Saturn's rings is identified as a one-armed spiral bending wave excited by Titan's -1:0 nodal inner vertical resonance. Ring partides in a bending wave move in coherently inclined orbits, warping the local mean plane of the rings. The Titan -1:0 wave is the only known bending wave that propagates outward, away from Saturn, and the only spiral wave yet observed in which the wave pattern rotates opposite to the orbital direction of the ring particles. It is also the first bending wave identified in ring C. Modeling the observed feature with existing bending wave theory gives a surface mass density of approximately 0.4 g/cm(2) outside the wave region and a local ring thickness of [unknown]5 meters, and suggests that surface mass density is not constant in the wave region. 相似文献
9.
采用时间序列分析理论。分析了人工林长白落叶松木材生长轮材性变异规律。对木材的化密度、晚材度和生长轮宽度进行变异规律的拟合。并对建模方法，模型参数选择以及检验进行讨论。结果表明，模型的拟合良度较好，不但能拟合出木材材性总体变化趋势，而且能拟合出细微变化周期性波动。 相似文献
10.
Smith BA Soderblom L Beebe R Boyce J Briggs G Bunker A Collins SA Hansen CJ Johnson TV Mitchell JL Terrile RJ Carr M Cook AF Cuzzi J Pollack JB Danielson GE Ingersoll A Davies ME Hunt GE Masursky H Shoemaker E Morrison D Owen T Sagan C Veverka J Strom R Suomi VE 《Science (New York, N.Y.)》1981,212(4491):163-191
As Voyager 1 flew through the Saturn system it returned photographs revealing many new and surprising characteristics of this complicated community of bodies. Saturn's atmosphere has numerous, low-contrast, discrete cloud features and a pattern of circulation significantly different from that of Jupiter. Titan is shrouded in a haze layer that varies in thickness and appearance. Among the icy satellites there is considerable variety in density, albedo, and surface morphology and substantial evidence for endogenic surface modification. Trends in density and crater characteristics are quite unlike those of the Galilean satellites. Small inner satellites, three of which were discovered in Voyager images, interact gravitationally with one another and with the ring particles in ways not observed elsewhere in the solar system. Saturn's broad A, B, and C rings contain hundreds of "ringlets," and in the densest portion of the B ring there are numerous nonaxisymmetric features. The narrow F ring has three components which, in at least one instance, are kinked and crisscrossed. Two rings are observed beyond the F ring, and material is seen between the C ring and the planet. 相似文献
11.
Gehrels T Baker LR Beshore E Blenman C Burke JJ Castillo ND Dacosta B Degewij J Doose LR Fountain JW Gotobed J Kenknight CE Kingston R McLaughlin G McMillan R Murphy R Smith PH Stoll CP Strickland RN Tomasko MG Wijesinghe MP Coffeen DL Esposito L 《Science (New York, N.Y.)》1980,207(4429):434-439
An imaging photopolarimeter aboard Pioneer 11, including a 2.5-centimeter telescope, was used for 2 weeks continuously in August and September 1979 for imaging, photometry, and polarimetry observations of Saturn, its rings, and Titan. A new ring of optical depth < 2 x 10(-3) was discovered at 2.33 Saturn radii and is provisionally named the F ring; it is separated from the A ring by the provisionally named Pioneer division. A division between the B and C rings, a gap near the center of the Cassini division, and detail in the A, B, and C rings have been seen; the nomenclature of divisions and gaps is redefined. The width of the Encke gap is 876 +/- 35 kilometers. The intensity profile and colors are given for the light transmitted by the rings. A mean particle size less, similar 15 meters is indicated; this estimate is model-dependent. The D ring was not seen in any viewing geometry and its existence is doubtful. A satellite, 1979 S 1, was found at 2.53 +/- 0.01 Saturn radii; the same object was observed approximately 16 hours later by other experiments on Pioneer 11. The equatorial radius of Saturn is 60,000 +/- 500 kilometers, and the ratio of the polar to the equatorial radius is 0.912 +/- 0.006. A sample of polarimetric data is compared with models of the vertical structure of Saturn's atmosphere. The variation of the polarization from the center of the disk to the limb in blue light at 88 degrees phase indicates that the density of cloud particles decreases as a function of altitude with a scale height about one-fourth that of the gas. The pressure level at which an optical depth of 1 is reached in the clouds depends on the single-scattering polarizing properties of the clouds; a value similar to that found for the Jovian clouds yields an optical depth of 1 at about 750 millibars. 相似文献
12.
HM Fischer E Pehlke G Wibberenz LJ Lanzerotti JD Mihalov 《Science (New York, N.Y.)》1996,272(5263):856-858
The energetic particles investigation carried by the Galileo probe measured the energy and angular distributions of the high-energy particles from near the orbit of Io to probe entry into the jovian atmosphere. Jupiter's inner radiation region had extremely large fluxes of energetic electrons and protons; intensities peaked at approximately2.2RJ (where RJ is the radius of Jupiter). Absorption of the measured particles was found near the outer edge of the bright dust ring. The instrument measured intense fluxes of high-energy helium ions (approximately62 megaelectron volts per nucleon) that peaked at approximately1.5RJ inside the bright dust ring. The abundances of all particle species decreased sharply at approximately1.35RJ; this decrease defines the innermost edge of the equatorial jovian radiation. 相似文献
13.
Burns JA 《Science (New York, N.Y.)》1968,159(3818):971-972
Many of the observed properties of Jupiter's decametric radiation may be explained by postulation that the inner Galilean satellites of Jupiter have magnetic properties that strongly distort Jupiter's magnetic field in the region of each satellite. Charged particles from Jupiter's radiation belts are trapped by these distorted fields and emit synchrotron radiation. 相似文献
14.
Porco CC West RA McEwen A Del Genio AD Ingersoll AP Thomas P Squyres S Dones L Murray CD Johnson TV Burns JA Brahic A Neukum G Veverka J Barbara JM Denk T Evans M Ferrier JJ Geissler P Helfenstein P Roatsch T Throop H Tiscareno M Vasavada AR 《Science (New York, N.Y.)》2003,299(5612):1541-1547
The Cassini Imaging Science Subsystem acquired about 26,000 images of the Jupiter system as the spacecraft encountered the giant planet en route to Saturn. We report findings on Jupiter's zonal winds, convective storms, low-latitude upper troposphere, polar stratosphere, and northern aurora. We also describe previously unseen emissions arising from Io and Europa in eclipse, a giant volcanic plume over Io's north pole, disk-resolved images of the satellite Himalia, circumstantial evidence for a causal relation between the satellites Metis and Adrastea and the main jovian ring, and information on the nature of the ring particles. 相似文献
15.
Observations have been made of several types of Liesegang patterns that are more complex than the usual concentric ring or parallel bands of precipitate. The structures observed show radial gaps, segmentation, irregular patterns within concentric rings, add the formation of spiral precipitation bands instead of sets of parallel Lisegang bands. 相似文献
16.
Hedberg K Hedberg L Bethune DS Brown CA Dorn HC Johnson RD DE Vries M 《Science (New York, N.Y.)》1991,254(5030):410-412
Electron diffraction patterns of the fullerene C(60) in the gaseous state have been obtained by volatilizing it from a newly designed oven-nozzle at 730 degrees C. The many peaks of the experimental radial distribution curve calculated from the scattered intensity are completely consistent with icosahedral symmetry for the free molecule. On the basis of this symmetry assumption, least-squares refinement of a model incorporating all possible interatomic distances led to the values r(g)(C(1)-C(2)) = 1.458(6) angstroms (A) for the thermal average bond length within the five-member ring (that is, for the bond fusing five- and six-member rings) and r(g)(C(1)-C(6)) = 1.401(10) A for that connecting five-member rings (the bond fusing six-member rings). The weighted average of the two bond lengths and the difference between them are the values 1.439(2) A and 0.057(6) A, respectively. The diameter of the icosahedral sphere is 7.113(10) A. The uncertainties in parentheses are estimated 2sigma values. 相似文献
17.
郑德森 《福建农林大学学报(自然科学版)》1990,(3)
甘蔗品种(种)叶片α-淀粉酶活性变化的基因型效应较大,12个供试材料间的差异明显,种间的差异大于品种间的差异,在个体发育过程中变化幅度较小。β-淀粉酶的活性变化与生长发育的关系较为密切,其变化呈典型的单峰曲线,活性的最高峰出现在甘蔗的旺长时期。几乎所有供试材料酶活性变化趋势是一致的,但变化幅度有差异。分蘖末期至伸长初期,同一材料的β-淀粉酶活性通常高于α-淀粉酶。 相似文献
18.
The gamma and delta rings have by far the largest radial perturbations of any of the nine known Uranian rings. These two rings deviate from Keplerian orbits, having typical root-mean-square residuals of about 3 kilometers (compared to a few hundred meters for the other seven known rings). Possible causes for the perturbations include nearby shepherd satellites and Lindblad resonances. If shepherd satellites are responsible, they could be as large as several tens of kilometers in diameter. The perturbation patterns of the gamma and delta rings have been examined for evidence of Lindblad resonances of azimuthal wave number m = 0, 1, 2, 3, and 4. The beta ring radial residuals are well matched by a 2:1 Lindblad resonance. If this represents a real physical phenomenon and is not an artifact of undersampling, then the most plausible interpretation is that there is an undiscovered satellite orbiting 76,522 +/- 8 kilometers from Uranus, with an orbital period of 15.3595 +/- 0.0001 hours and a radius of 75 to 100 kilometers. Such a satellite would be easily detected by the Voyager spacecraft when it encounters Uranus. The 2:1 resonance location is 41 +/- 9 kilometers inside the delta ring, which makes it unlikely that the resonance is due to a viscous instability within the ring. In contrast, no low-order Lindblad resonance matches the gamma ring perturbations, which are probably caused by one or more shepherd satellites large enough to be clearly visible in Voyager images. 相似文献
19.
JH Waite GR Gladstone WS Lewis P Drossart TE Cravens AN Maurellis BH Mauk S Miller 《Science (New York, N.Y.)》1997,276(5309):104-108
Observations with the High Resolution Imager on the Rontgensatellit reveal x-ray emissions from Jupiter's equatorial latitudes. The observed emissions probably result from the precipitation of energetic (>300 kiloelectron volts per atomic mass unit) sulfur and oxygen ions out of Jupiter's inner radiation belt. Model calculations of the energy deposition by such heavy ion precipitation and of the resulting atmospheric heating rates indicate that this energy source can contribute to the high exospheric temperatures(>800 kelvin at 0.01 microbar) measured by the Galileo probe's Atmospheric Structure Instrument. Low-latitude energetic particle precipitation must therefore be considered, in addition to other proposed mechanisms such as gravity waves and soft electron precipitation, as an important source of heat for Jupiter's thermosphere. 相似文献
20.
The spokes are intermittently appearing radial markings in Saturn's B ring that are believed to form when micrometer-sized dust particles are levitated above the ring by electrostatic forces. First observed by the Voyagers, the spokes disappeared from October 1998 until September 2005, when the Cassini spacecraft saw them reappear. The trajectories of the charged dust particles comprising the spokes depend critically on the background plasma density above the rings, which is a function of the solar elevation angle. Because the rings are more open to the Sun now than when Voyager flew by, the charging environment above the rings has prevented the formation of spokes until very recently. We show that this notable effect is capable of stopping spoke formation entirely and restricting the size of the particles in the spokes. 相似文献