Ices on the surface of triton

The near-infrared spectrum of Triton reveals ices of nitrogen, methane, carbon monoxide, and carbon dioxide, of which nitrogen is the dominant component. Carbon dioxide ice may be spatially segregated from the other more volatile ices, covering about 10 percent of Triton's surface. The absence of ices of other hydrocarbons and nitriles challenges existing models of methane and nitrogen photochemistry on Triton.     

Evidence for a low surface temperature on pluto from millimeter-wave thermal emission measurements

Thermal continuum emission from the Pluto-Charon system has been detected at wavelents of 800 and 1300 micrometers, and significant upper limits have been obtained at 450 and 1100 micrometers. After the subtraction of emission from Charon, the deduced surface temperature of much of Pluto is between 30 and 44 kein, probably near 35 to 37 kelvin. This range is significantly cooler than what radiative equilibrium models have suged and cooler than the surface temperature derived by the Infrared Astronomy Satellite. The low temperature indicates that methane cannot be present at the microbar pressure levels indicated by the 1988 stellar occultation measurements and that the methane features in Pluto's spectrum are from solid, not gas-phase, absorptions. This result is evidence that Pluto's atmosphere is dominated by nitrogen or carbon monoxide rather than methane.     

Evidence for crystalline water and ammonia ices on Pluto's satellite charon

Observations have resolved the satellite Charon from its parent planet Pluto, giving separate spectra of the two objects from 1.0 to 2.5 micrometers. The spectrum of Charon is found to be different from that of Pluto, with water ice in crystalline form covering most of the surface of the satellite. In addition, an absorption feature in Charon's spectrum suggests the presence of ammonia ices. Ammonia ice-water ice mixtures have been proposed as the cause of flowlike features observed on the surfaces of many icy satellites. The existence of such ices on Charon may indicate geological activity in the satellite's past.     

Fast ion bombardment of ices and its astrophysical implications

Ices such as water, carbon dioxide, and methane are now known to be pervasive constituents of the solar system and probably of the interstellar medium as well. Many of these ices and ice-covered surfaces are exposed to bombardment by the energetic ions of space. Laboratory experiments have been carried out to study the effects of such bombardment. Surprisingly efficient erosion of ice layers is associated with electronic excitation of the ices by the ions. These results are a challenge to an understanding of the physical processes involved and have implications for a number of astrophysical problems of current interest.     

Spectrophotometry of pluto-charon mutual events: individual spectra of pluto and charon

Time-resolved spectra of the 3 March and 4 April 1987 mutual events of Pluto and its satellite Charon were obtained with spectral coverage from 5,500 to 10,000 angstroms with 25 angstrom spectral resolution. Since both events were total occultations of Charon by Pluto, spectra were obtained of the anti-Charon-facing hemisphere of Pluto, with no contribution from Charon during totality. On 4 April, a combined spectrum of Pluto and Charon immediately before first contact was also obtained. The spectrum of the Pluto-facing hemisphere of Charon was extracted by differencing the pre-event and totality spectra. The spectra were reduced to reflectances by ratioing them to spectra of solar analog stars. Charon has a featureless reflectance spectrum, with no evidence of methane absorption. Charon's reflectance appears neutral in color and corresponds to a geometric albedo of approximately 0.37 at 6000 angstroms. The Pluto reflectance spectrum displays methane absorption bands at 7300, 7900, 8400, 8600, and 8900 angstroms and is red in color, with a geometric albedo of approximately 0.56 at 6000 angstroms. The signal-to-noise ratios of the eclipse spectra were not high enough to unambiguously identify the weaker methane band at 6200 angstroms.     

Numerical evidence that the motion of pluto is chaotic

The Digital Orrery has been used to perform an integration of the motion of the outer planets for 845 million years. This integration indicates that the long-term motion of the planet Pluto is chaotic. Nearby trajectories diverge exponentially with an e-folding time of only about 20 million years.     

Hemispherical color differences on pluto and charon

Time-resolved multicolor photometric observations of Pluto-Charon mutual events have been used to derive individual colors for these two bodies and to investigate the degree of color differences between their synchronous facing and opposite hemispheres. Pluto is significantly redder than Charon, where direct measurements of the anti-Charon hemisphere of Pluto and the Pluto-facing hemisphere of Charon yield B-V magnitudes of 0.867 +/- 0.008 and 0.700 +/- 0.010, respectively. Both Pluto and Charon are found to have relatively uniform longitudinal color distributions with lsigma upper limits of 2% and 5%, respectively, for any large-scale hemispherical color asymmetries. Thus, a previous suspicion of a significant color asymmetry on Charon is not confirmed. Instead the data may be attributed to a direct detection of polar caps on Pluto.     

Atmospheric physics and Earth observations: sample performance of the grille spectrometer

The grille spectrometer observed the setting and rising sun 18 times during the Spacelab 1 mission. In addition to solar absorption lines, many of which had not been observed before, atmospheric spectral absorptions due to carbon monoxide and carbon dioxide were observed at heights tangent to the thermosphere (greater than 85 kilometers), and absorptions due to ozone, water, methane, and nitrous oxide were observed in the mesosphere (greater than 50 kilometers). The strongly coupled molecules NO-NO(2) and HC1-HF were observed as pairs in the stratosphere. Methane is presented as an example of the instrumental operations because of the characteristic aspect of the Q branch of its v(3) band.     

茶树菇对不同碳氮营养源的利用

通过试验探讨茶树菇对碳源和氮源的利用。结果表明,茶树菇菌丝生长的最适碳源是可溶性淀粉,其次是蔗糖、葡萄糖;最适氮源是蛋白胨,其次是酵母膏、麸皮。     

Frequencies of occultations of stars by planets, satellites, and asteroids

Calculations show that several occultations of stars by the large satellites of the outer planets, Pluto, and the large asteroids could be observed each decade with existing equipment at Earth-based telescopes. A systematic program of occultation predictions and observations is urged in order to improve our knowledge about the atmospheres, sizes, shapes, topography, and positions of these poorly understood bodies, in support of forthcoming spacecraft missions to the outer solar system.     

Atmospheric carbon dioxide: its role in maintaining phytoplankton standing crops

The rate of invasion of carbon dioxide into an artificially eutrophic Canadian Shield lake with insufficient internal sources of carbon was determined by two methods: measuring the carbon : nitrogen : phosphorus ratios of seston after weekly additions of nitrogen and phosphorus, and measuring the loss of radon-222 tracer from the epilimnion. Both methods gave an invasion rate of about 0.2 gram of carbon per square meter per day. The results demonstrate that invasion of atmospheric carbon dioxide may be sufficient to permit eutrophication of any body of water receiving an adequate supply of phosphorus and nitrogen.     

Major role of the cyanobacterium trichodesmium in nutrient cycling in the north atlantic ocean

The diazotrophic cyanobacterium Trichodesmium is a large (about 0.5 by 3 millimeters) phytoplankter that is common in tropical open-ocean waters. Measurements of abundance, plus a review of earlier observations, indicate that it, rather than the picophytoplankton, is the most important primary producer (about 165 milligrams of carbon per square meter per day) in the tropical North Atlantic Ocean. Furthermore, nitrogen fixation by Trichodesmium introduces the largest fraction of new nitrogen to the euphotic zone, approximately 30 milligrams of nitrogen per square meter per day, a value exceeding the estimated flux of nitrate across the thermocline. Inclusion of this organism, plus the abundant diazotrophic endosymbiont Richelia intracellularis that is present in some large diatoms, in biogeochemical studies of carbon and nitrogen may help explain the disparity between various methods of measuring productivity in the oligotrophic ocean. Carbon and nitrogen fixation by these large phytoplankters also introduces a new paradigm in the biogeochemistry of these elements in the sea.     

长沙市城区碳收支平衡的空间差异性研究

利用量化统计方法对长沙市芙蓉区、天心区、岳麓区、开福区、雨花区、望城区现阶段人类呼吸作用和化石燃料产生的碳排放与植被碳吸收量进行比较,探讨各区碳吸收率的差异性。结果表明,雨花区的碳排放最大,占全市的24.77%;而芙蓉区和天心区碳吸收率最小,分别只有1.87%和12.08%。相对而言,望城区和岳麓区的碳平衡保持最好。全市碳吸收率仅为48.16%。若要达到市区整体的碳收支平衡,还需增加84297.32 hm2林地以吸收多余的二氧化碳。按长沙市经济发展规划,2020年要维持目前48.16%的碳吸收率,在绿地结构不变的前提下,必须要增加更多绿地面积,全市绿地覆盖率需达到94.99%以上。这就需要对植被结构进行优化,并降低能耗,增加绿化率至60%,并在市外预留134099.02 hm2林地吸收多余的二氧化碳。     

A giant impact origin of Pluto-Charon

Pluto and its moon, Charon, are the most prominent members of the Kuiper belt, and their existence holds clues to outer solar system formation processes. Here, hydrodynamic simulations are used to demonstrate that the formation of Pluto-Charon by means of a large collision is quite plausible. I show that such an impact probably produced an intact Charon, although it is possible that a disk of material orbited Pluto from which Charon later accumulated. These findings suggest that collisions between 1000-kilometer-class objects occurred in the early inner Kuiper belt.     

Improved orbital and physical parameters for the pluto-charon system

Analysis of the observations of several Pluto-Charon occultation and transit events in 1985 and 1986 has provided a more detailed knowledge of the system. The sum of the radii of Pluto and Charon is 1786 +/- 19 kilometers, but the individual radii are somewhat more poorly determined; Pluto is 1145 +/- 46 kilometers in radius and Charon is 642 +/- 34 kilometers in radius. The mean density of the system is 1.84 +/- 0.19 grams per cubic centimeter, implying that more than half of the mass is due to rock. Charon appears to have hemispheres of two different colors, the Plutofacing side being neutral in color and the opposite hemisphere being a reddish color similar to Pluto.     

长期施肥对稻田土壤活性有机碳和氮的影响

土壤活性有机碳、氮是土壤有机碳、氮中最活跃的组分,在土壤碳、氮循环过程中具有重要作用。以湖南3个长期定位试验点(桃源、宁乡、桃江)为研究对象,分析测定表层土壤MBC、MBN、DOC、DON,研究长期施肥对土壤活性有机碳、氮(MBC+DOC,MBN+DON)的影响。结果表明,长期施用化肥及配施有机肥均能提高土壤活性有机碳、氮的含量。与对应的无肥处理(CK)相比,长期单施化肥(NPK)使土壤活性有机碳、氮的提高幅度分别为3.3%~21.0%和3.3%~27.1%,长期有机肥施用提高幅度分别为48.7%~84.8%和17.9%~105.8%,且土壤活性有机碳、氮含量随有机肥施用量的提高而增加,3个试验点活性有机碳大小顺序为桃源>宁乡>桃江。土壤活性有机碳与土壤有机碳(SOC)的累积速率呈显著正相关关系(P<0.05),而与SOC的含量关系不大。桃源土壤粘粒含量较高可能是土壤SOC累积速率快的主要原因;宁乡和桃江的粘粒含量和有机碳投入量相差不大,桃江较高的初始SOC水平影响了SOC积累速率;桃源和宁乡试验点的土壤活性氮含量相差不大,约是桃江的1.8倍。与土壤全氮(TN)相比,全氮的积累速率与土壤活性氮的关系更为密切,两者间有极显著的相关关系(P<0.01)。     

Mass of pluto

Analysis of the observations of Neptune indicates a reciprocal mass of Pluto of 1,812,000 (0.18 Earth masses). If the density is the same as that of Earth, the diameter would be 7200 kilometers. If 6400 kilometers is accepted (from other sources) as the upper limit of the diameter, then Pluto must be at least 1.4 times as dense as Earth.     

The surface composition of charon: tentative identification of water ice

The 3 March 1987 Charon occultation by Pluto was observed in the infrared at 1.5, 1.7, 2.0, and 2.35 micrometers. Subtraction of fluxes measured between second and third contacts from measurements made before and after the event has yielded individual spectral signatures for each body at these wavelengths. Charon's surface appears depleted in methane relative to Pluto. Constancy of flux at 2.0 micrometers throughout the event shows that Charon is effectively black at this wavelength, which is centered on a very strong water absorption band. Thus, the measurements suggest the existence of water ice on Pluto's moon.     

IRAS Serendipitous Survey Observations of Pluto and Charon

On 16 August 1983 the Infrared Astronomical Satellite made two separate pointed observations of Pluto and its moon Charon. Because of the small angular displacement of the system between the times of measurement, the Pluto-Charon system was identified as a source in the Serendipitous Survey (SSC 14029+0518). Detections were made at 60 and 100 micrometers with color-corrected flux densities of 581 +/- 58 and 721 +/- 123 millijanskys, respectively. Pluto is best described as having a dark equatorial band, and brighter polar caps of methane ice extending to +/-45 degrees latitude, at most. An upper limit of approximately 9 meter-amagats is placed on the column abundance of a methane atmosphere on Pluto, which is comparable to recent upper limits based on independent ground-based spectroscopy.     

Impacts of atmospheric anthropogenic nitrogen on the open ocean

Increasing quantities of atmospheric anthropogenic fixed nitrogen entering the open ocean could account for up to about a third of the ocean's external (nonrecycled) nitrogen supply and up to approximately 3% of the annual new marine biological production, approximately 0.3 petagram of carbon per year. This input could account for the production of up to approximately 1.6 teragrams of nitrous oxide (N2O) per year. Although approximately 10% of the ocean's drawdown of atmospheric anthropogenic carbon dioxide may result from this atmospheric nitrogen fertilization, leading to a decrease in radiative forcing, up to about two-thirds of this amount may be offset by the increase in N2O emissions. The effects of increasing atmospheric nitrogen deposition are expected to continue to grow in the future.