Search for interstellar superheavy hydrogen

Models for fundamental physical interactions allow for the existence of stable or nearly stable elementary particles much heavier than the proton. Stellar spectra were searched for a positively charged superheavy particle, X(+), which, with a bound electron, should appear as apparently superheavy neutral hydrogen in the interstellar medium. An upper limit for the abundance of X relative to normal hydrogen in the line of sight toward the bright star gamma Cassiopeiae is 2 x 10(-8).     

Chemical signatures for superheavy elementary particles

Models of unified fundamental interactions suggest the existence of many particles in the mass range 10 x 10(9) to 100 x 10(12) electron volts. Among these may be charged particles, X(+/-), that are stable or nearly so. The X(+,)s would form superheavy hydrogen, while the X(-,)s would bind to nuclei. Chemical isolation of naturally occurring technetium, promethium, actinium, protactinium, neptunium, or americium would indicate the presence of superheavy particles in the forms RuX(-), SmX(-), (232)ThX(-), (235,236,238)UX(-), (244)PuX(-), or (247)CmX(-). Other substances worth searching for include superheavy elements with the chemical properties of boron, fluorine, manganese, beryllium, scandium, vanadium, lithium, neon, and thallium.     

Barium isotopes in allende meteorite: evidence against an extinct superheavy element

Carbon and chromite fractions from the Allende meteorite that contain isotopically anomalous xenon-131 to xenon-136 (carbonaceous chondrite fission or CCF xenon) at up to 5 x 10(11) atoms per gram show no detectable isotopic anomalies in barium-130 to barium-138. This rules out the possibility that the CCF xenon was formed by in situ fission of an extinct superheavy element. Apparently the CCF xenon and its carbonaceous carrier are relics from stellar nucleosynthesis.     

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.     

Superheavy elements: a crossroads

The failure to synthesize superheavy elements by using complete fusion reactions is most likely understandable in terms of the low survival probabilities of the superheavy precursors formed in these reactions or (in some cases) the failure to achieve complete fusion. Further attempts to synthesize these elements by using complete fusion or deep inelastic transfer reactions, or both, are discussed in light of these results.     

Abundance of alkali metals, alkaline and rare earths, and strontium-87/ strontium-86 ratios in lunar samples

The variation in trace element abundance patterns indicates that lunar igneous rocks are the product of extensive igneous fractionation. Variations in the Sr(87)/ Sr(86) ratio indicate that these rocks crystallized 3.5+/-0.3 x 10(9) years ago.     

Isotopic abundances of actinide elements in lunar material

The abunldanzces of uranium and thorium were measured mass spectrometrically as 0.59 +/- 0.02 and 2.24 +/- 0.06 parts per million, respectively, in the fines of Apollo 11 builk sample. The ratio (235)U/(238)U was 0.007258 +/- 0.000016, in agreement with terrestrial uranium. The following upper limits were set: (236)U/(238)U相似文献   

Escape of hydrogen from venus

Recombination of O(2)(+) represents a source of fast oxygen atoms in Venus' exosphere, and subsequent collisions of oxygen atoms with hydrogen atoms lead to escape of about 10(7) hydrogen atoms per square centimeter per second. Escape of deuterium atoms is negligible, and the ratio of deuterium to hydrogen should increase with time. It is suggested that the mass-2 ion observed by Pioneer Venus is D(+), which implies a ratio of deuterium to hydrogen in the contemporary atmosphere of about 10(-2), an initial ratio of 5 x 10(-5) and an original H(2)O abundance not less than 800 grams per square centimeter.     

Deuterated methane observed on saturn

Absorptions for the V(2) band of deuterated methane (CH(3)D) have been observed in the 5-micron spectrum of Saturn, obtained with a Fourier transform spectrometer. Analysis of the band yields a CH(3)D abundance of 2.6 +/- 0.8 centimeter-amagat and a temperature of 175 +/- 30 K for the mean level of spectroscopic line formation. This temperature indicates that a substantial portion of Saturn's flux at 5 microns is due to thermal radiation, and that we are therefore looking fairly deep into its atmosphere, as is the case for the Jupiter 5-micron window. This CH(3)D abundance leads to a deuteriumlhydrogen ratio of about 2 x 10(-5) in Saturn's atmosphere. This ratio is much lower than the terrestrial value but comparable to that determined for Jupiter and may be taken as representative of the deuteriumlhydrogen ratio in the solar system at the time of its formation.     

Mercury's Atmosphere from Mariner 10: Preliminary Results

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.     

A meteoritic component rich in volatile elements: its characterization and implications

An unusual carbon-rich material found in the Abee meteorite is highly enriched in volatile elements, by factors of 10(4) relative to the case for nonvolatile elements. Volatile-rich material of this type might form in the solar nebula toward the end of accretion, when small amounts of residual dust acquire all the uncondensed volatile elements. The mercury enrichment factor of 8500 could explain the paradox of the excess abundance of this element in meteorites.     

The ancient lunar core dynamo

Lunar paleomagnetism provides evidence for the existence of an ancient lunar magnetic field generated in an iron core. Paleointensity experiments give a surface field of 1.3 gauss, 4.0 x 10(9) years ago, subsequently decreasing exponentially. Thermodynamic arguments give a minimum value of the heat source in the core at that time: known sources, radioactive and other, are quantitatively implausible, and it is suggested that superheavy elements were present in the early moon.     

Exinct superheavy element in meteorites: attempted characterization

If the unexplained fission xenon component in meteorites is due to a volatile superheavy element, this element must have had a heat of vaporization of 54 +/- 3 kilocalories per mole and a normal boiling point of 2500 degrees +/- 400 degrees K. The prime candidates are elements 111 and 115, followed by 113, 114, 112, and 116. Elements 105 to 110 are not volatile enough and can therefore be excluded.     

Magnetic properties of lunar sample 10048-22

The natural remanent magnetization (3.7 x 10(4) electromagnetic units per cubic centimeter) and the susceptibility per cubic centimeter (6.3 x 10(-13)) of an 18.5-gram breccia specimen were determined with instrumentation and techniques currently used in paleomagnetism. The relatively low magnetic stability of the rock in the earth's field and in alternating demagnetizing fields precludes considering it as a reliable carrier of paleomagnetism. A magnetic balance study yields an unusually high Curie temperature (750 degrees C) which is possibly diagnostic of metallic Fe containing less than 5 percent nickel. The estimated relative abundance of the iron in the sample is about 0.5 percent.     

Voyager radio science observations of neptune and triton

The Voyager 2 encounter with the Neptune system included radio science investigations of the masses and densities of Neptune and Triton, the low-order gravitational harmonics of Neptune, the vertical structures of the atmospheres and ionospheres of Neptune and Triton, the composition of the atmosphere of Neptune, and characteristics of ring material. Demanding experimental requirements were met successfully, and study of the large store of collected data has begun. The initial search of the data revealed no detectable effects of ring material with optical depth tau [unknown] 0.01. Preliminary representative results include the following: 1.0243 x 10(26) and 2.141 x 10(22) kilograms for the masses of Neptune and Triton; 1640 and 2054 kilograms per cubic meter for their respective densities; 1355 +/- 7 kilometers, provisionally, for the radius of Triton; and J(2) = 3411 +/- 10(x 10(-6)) and J(4) = -26(+12)(-20)(x10(-6)) for Neptune's gravity field (J>(2) and J(4) are harmonic coefficients of the gravity field). The equatorial and polar radii of Neptune are 24,764 +/- 20 and 24,340 +/- 30 kllometers, respectively, at the 10(5)-pascal (1 bar) pressure level. Neptune's atmosphere was probed to a pressure level of about 5 x 10(5) pascals, and effects of a methane cloud region and probable ammonia absorption below the cloud are evident in the data. Results for the mixing ratios of helium and ammonia are still being investigated; the methane abundance below the clouds is at least 1 percent by volume. Derived temperature-pressure profiles to 1.2 x 10(5) pascals and 78 kelvins (K) show a lapse rate corresponding to "frozen" equilibrium of the para- and ortho-hydrogen states. Neptune's ionosphere exhibits an extended topside at a temperature of 950 +/- 160 K if H(+) is the dominant ion, and narrow ionization layers of the type previously seen at the other three giant planets. Triton has a dense ionosphere with a peak electron concentration of 46 x 10(9) per cubic meter at an altitude of 340 kilometers measured during occultation egress. Its topside plasma temperature is about 80 +/- 16 K if N(2)(+) is the principal ion. The tenuous neutral atmosphere of Triton produced distinct signatures in the occultation data; however, the accuracy of the measurements is limited by uncertainties in the frequency of the spacecraft reference oscillator. Preliminary values for the surface pressure of 1.6 +/- 0.3 pascals and an equivalent isothermal temperature of 48 +/- 5 K are suggested, on the assumption that molecular nitrogen dominates the atmosphere. The radio data may be showing the effects of a thermal inversion near the surface; this and other evidence imply that the Triton atmosphere is controlled by vapor-pressure equilibrium with surface ices, at a temperature of 38 K and a methane mixing ratio of about 10(-4).     

Discovery of sodium in the atmosphere of mercury

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.     

A search for iridium abundance anomalies at two late cambrian biomere boundaries in Western utah

Iridium concentrations have been measured in samples taken across two Late Cambrian biomere boundaries (crisis zones) in search of evidence for possible elemental abundance anomalies similar to the one observed at the Cretaceous-Tertiary boundary. Sampling was performed in uplifted marine limestone deposits in the House Range of western Utah. Although the two trilobite-brachiopod extinction boundaries could be assigned to +/-4 millimeters of vertical section by laboratory examination of the rocks, only background amounts of iridium (2 x 10(-12) to 17 x 10(-12) gram per gram of whole rock) were observed.     

中国近岸海域船舶压载水浮游植物特征分析

船舶压载水作为不同海域之间浮游植物传播的重要途径,可能会引发一系列生态风险。2015年4月到2016年7月选取停靠在上海洋山港且上一压载地为中国近岸海域的6艘船舶,分析船舶压载水浮游植物。共采集到浮游植物3门22种,包括硅藻门17种、甲藻门4种、金藻门1种,优势种为硅藻。其中渤海海域压载水浮游植物2门5种,包括硅藻门4种、甲藻门1种,丰度为9.66×10~2cells/L;黄海海域3门10种,包括硅藻门7种、甲藻门2种、金藻门1种,丰度为8.955×10~2cells/L;东海海域2门4种包括硅藻门3种、金藻门1种,丰度为6.83×10~2cells/L;南海海域2门11种包括硅藻门6种、甲藻门5种,丰度为22.915×10~2cells/L。调查发现到港船舶压载水中浮游植物与其压载地的浮游植物间存在差异,压载水中浮游植物种类组成可能受压载地当地受气团、季节等因素影响。压载水中少量物种为传入其他海区的外来物种或其它海区的赤潮种。     

Detection of molecular oxygen on Mars

Molecular oxygen was detected in martian spectra near 7635 angstroms and its abundance measured both during and after the 1971 dust storm. Its column abundance in the clear martian atmosphere is about 10.4 +/- 1.0 centimeters amagat, giving a mixing ratio of molecular oxygen to carbon dioxide of 1.3 x 10-(3). The mixing ratio of molecular oxygen to carbon monoxide (1.4 +/- 0.3) is quite different from the value of 0.5 that would result from the photolysis of a pure carbon dioxide atmosphere, which indicates that there is or was a net source of oxygen relative to carbon (probably water) in the martian atmosphere.     

Terrestrial ages of four allan hills meteorites: consequences for antarctic ice

The terrestrial ages of three Allan Hills meteorites are between 3 x 10(4) and 3 x 10(5) years and one is (1.54(-0.28)(+0.14)) x 10(6) years old. The Antarctic ice sheet is therefore older than (1.54(-0.28)(+0.14)) x 10(6) years and the meteorite accumulation process at Allan Hills probably began between 3 x 10(4) and 3 x 10(5)years ago.