Methane-derived marine carbonates of pleistocene age

In some calcium carbonate-bearing sandstones from the edge of the continental shelf off the northeast United States, the deltaC(13) range is from -30 and -60 per mil for both aragonite and high-magnesium calcite. The deltaC(13) of co-existing shells of Modiolus sp. is normal (+ 1.7 to -2.7 per mil). The deltaO(18) values of around + 3.5 per mil in all samples suggest deposition at temperatures around 0 degrees C. Quaternary methane oxidized either chemically or microbiologically to carbon dioxide is the probable source of carbon in these carbonates.     

Mariners 6 and 7: radio occultation measurements of the atmosphere of Mars

Radio occultation measurements with Mariners 6 and 7 provided refractivity data in the atmosphiere of Mars at four points above its surface. For an atmosphere consisting predominantly of carbon dioxide, surface pressures between 6 and 7 millibars are obtained at three of the points of measurement, and 3.8 at the fourth, indicating an elevation of 5 to 6 kilometers. The temperature profile measured by Mariner 6 near the equator in the daytime indicates temperatures in the stratosphere about 100 degrees K warmer than those predicted by theory. The measurements of Mariner 6 taken at 79 degrees N at the beginning of polar night indicate that conditions are favorable for the condensation of carbon dioxide at almost all altitudes. Mariner 7 measurements taken at 58 degrees S in daytime and 38 degrees N at night also show that carbon dioxide condensation is possible at altitudes above about 25 kilometers. Measurements of the electron density in the ionosphere show that the upper atmosphere is substantially warmer than it was in 1965, possibly because of increased solar activity and closer proximity to the sun.     

Carbon dioxide hydrate and floods on Mars

Ground ice on Mars probably consists largely of carbon dioxide hydrate, CO(2) . 6H(2)O. This hydrate dissociates upon release of pressure at temperatures between 0 degrees and 10 degrees C. The heat capacity of the ground would be sufficient to produce up to 4 percent (by volume) of water at a rate equal to that at which it can be drained away. Catastrophic dissociation of carbon dioxide hydrate during some past epoch when the near surface temperature was in this range would have produced chaotic terrain and flood channels.     

Is ozone trapped in the solid carbon dioxide polar cap of Mars?

Laboratory experiments show that solid carbon dioxide is an effective trap for ozone at temperatures as high as 156 degrees K. Ultraviolet reflection-absorption spectra of ozone in solid carbon dioxide at 127 degrees K indicate that the ozone observed over the polar cap of Mars may be trapped in solid carbon dioxide.     

Oil shales and carbon dioxide

During retorting of oil shales in the western United States, carbonate minerals are calcined, releasing significant amounts of carbon dioxide. Residual organic matter in the shales may also be burned, adding more carbon dioxide to the atmosphere. The amount of carbon dioxide produced depends on the retort process and the grade and mineralogy of the shale. Preliminary calculations suggest that retorting of oil shales from the Green River Formation and burning of the product oil could release one and one-half to five times more carbon dioxide than burning of conventional oil to obtain the same amount of usable energy. The largest carbon dioxide releases are associated with retorting processes that operate at temperatures greater than about 600 degrees C.     

Carbon, carbides, and methane in an apollo 12 sample

Total carbon in the Apollo 12 sample 12023 fines was 110 micrograms per gram of sample with a carbon isotopic abundance delta(13)C (relative to the Pee Dee belemnite standard) of +12 per mil. Hydrolysis of the fines with deuterium chloride yielded undeuterated methane along with deuterated hydrocarbons, thus confirming the presence of 7 to 21 micrograms of carbon per gram of sample as carbide and about 2 micrograms of carbon per gram of sample as indigenous methane. After vacuum pyrolysis of the fines to 1100 degrees C the following gases were detected in the relative abundance: carbon monoxide carbon dioxide methane. Variations of the delta(13)C value with the pyrolysis temperature indicated the presence of carbon with more than one range of isotopic values. The observed delta(13)C value of +14 per mil for lunar carbide is much higher than that of carbide in meteorites. These results suggest that lunar carbide is either indigenous to the moon or a meteoritic contribution that has been highly fractionated isotopically.     

Deep-sea authigenic calcite and dolomite

Crystals of calcite and, in one case, of dolomite up to 90 microm in size are dispersed in pelagic red clay at several sites on the floor of the South Pacific Ocean. They were analyzed by microscopic, x-ray diffraction, electron x-ray microprobe, and oxygen isotopic techniques. These carbonates are authigenic and were probably precipitated from hydrothermal solutions connected with deep-sea volcanic activity.     

Deposition of conformal copper and nickel films from supercritical carbon dioxide

Device-quality copper and nickel films were deposited onto planar and etched silicon substrates by the reduction of soluble organometallic compounds with hydrogen in a supercritical carbon dioxide solution. Exceptional step coverage on complex surfaces and complete filling of high-aspect-ratio features of less than 100 nanometers width were achieved. Nickel was deposited at 60 degrees C by the reduction of bis(cyclopentadienyl)nickel and copper was deposited from either copper(I) or copper(II) compounds onto the native oxide of silicon or metal nitrides with seed layers at temperatures up to 200 degrees C and directly on each surface at temperatures above 250 degrees C. The latter approach provides a single-step means for achieving high-aspect-ratio feature fill necessary for copper interconnect structures in future generations of integrated circuits.     

A high-resolution record of holocene climate change in speleothem calcite from cold water cave, northeast iowa

High-precision uranium-thorium mass spectrometric chronology and (18)O-(13)C isotopic analysis of speleothem calcite from Cold Water Cave in northeast Iowa have been used to chart mid-Holocene climate change. Significant shifts in dagger(18)O and dagger(13)C isotopic values coincide with well-documented Holocene vegetation changes. Temperature estimates based on (18)O/(16)O ratios suggest that the climate warmed rapidly by about 3 degrees C at 5900 years before present and then cooled by 4 degrees C at 3600 years before present. Initiation of a gradual increase in dagger(13)C at 5900 years before present suggests that turnover of the forest soil biomass was slow and that equilibrium with prairie vegetation was not attained by 3600 years before present.     

Geomicrobiology of deep-sea hydrothermal vents

During the cycling of seawater through the earth's crust along the mid-ocean ridge system, geothermal energy is transferred into chemical energy in the form of reduced inorganic compounds. These compounds are derived from the reaction of seawater with crustal rocks at high temperatures and are emitted from warm (相似文献   

Search for organic and volatile inorganic compounds in two surface samples from the chryse planitia region of Mars

Two surface samples collected from the Chryse Planitia region of Mars were heated to temperatures up to 500 degrees C, and the volatiles that they evolved were analyzed with a gas chromatograph-mass spectrometer. Only water and carbon dioxide were detected. This implies that organic compounds have not accumulated to the extent that individual components could be detected at levels of a few parts in 10(9) by weight in our samples. Proposed mechanisms for the accumulation and destruction of organic compounds are discussed in the light of this limit.     

Infrared Radiation from the Atmosphere over the Arctic Ocean

The emission spectrum of the atmosphere over the Arctic Ocean was observed during a period when atmosphere and snow surface temperatures were about -40 degrees C. The main contributions to the emission in the 5-to 21-micron range came from ozone and carbon dioxide, with water vapor playing a minor part.     

Volatile-rich lunar soil: evidence of possible cometary impact

A subsurface Apollo 16 soil, 61221, is much richer in volatile compounds than soils from any other locations or sites as shown by thermal analysis-gas release measurements. A weight loss of 0.03 percent during the interval 175 degrees to 350 degrees C was associated with the release of water, carbon dioxide, methane, hydrogen cyanide, hydrogen, and minor amounts of hydrocarbons and other species. These volatile components may have been brought to this site by a comet, which may have formed North Ray crater.     

Blood function in the hydrothermal vent vestimentiferan tube worm

Extracellular hemoglobin in the whole blood of Riftia pachyptila has a high oxygen affinity (P50 = 1.8 millimeters of mercury at 3 degrees C), a moderate decrease in oxygen affinity at higher temperatures (P50 = 2.7 millimeters of mercury at 14 degrees C), a small effect of carbon dioxide on oxygen affinity (Delta log P50/Delta pH =-0.12), and a high oxygen carrying capacity (up to 11 milliliters of oxygen per 100 milliliters of blood). These characteristics are compatible with the high oxygen demand of chemoautotrophic metabolism in the variable vent environment.     

Role of seasonality in the evolution of climate during the last 100 million years

A simple climate model has been used to calculate the effect of past changes in the land-sea distribution on the seasonal cycle of temperatures during the last 100 million years. Modeled summer temperatures decreased over Greenland by more than 10 degrees C and over Antarctica by 5 degrees to 8 degrees C. For the last 80 million years, this thermal response is comparable in magnitude to estimated atmospheric carbon dioxide effects. Analysis of paleontological data provides some support for the proposed hypothesis that large changes due to seasonality may have sometimes resulted in an ice-free state due to high summer temperature rather than year-round warmth. Such "cool" non-glacials may have prevailed for as much as one-third of the last 100 million years.     

Time and metamorphic petrology: calcite to aragonite experiments

Although the equilibrium phase relations of many mineral systems are generally well established, the rates of transformations, particularly in polycrystalline rocks, are not. The results of experiments on the calcite to aragonite transformation in polycrystalline marble are different from those for earlier experiments on powdered and single-crystal calcite. The transformation in the polycrystalline samples occurs by different mechanisms, with a different temperature dependence, and at a markedly slower rate. This work demonstrates the importance of kinetic studies on fully dense polycrystalline aggregates for understanding mineralogic phase changes in nature. Extrapolation of these results to geological time scales suggests that transformation of calcite to aragonite does not occur in the absence of volatiles at temperatures below 200 degrees C. Kinetic hindrance is likely to extend to higher temperatures in more complex transformations.     

Reaction of plutonium dioxide with water: formation and properties of PuO(2+x)

Results show that PuO(2+x), a high-composition (x 相似文献   

Temperature measurements in carbonatite lava lakes and flows from oldoinyo lengai, Tanzania

The petrogenesis of carbonatites has important implications for mantle processes and for the magmatic evolution of mantle melts rich in carbon dioxide. Oldoinyo Lengai, Tanzania, is the only active carbonatite volcano on Earth. Its highly alkalic, sodium-rich lava, although different in composition from the more common calcium-rich carbonatites, provides the opportunity for observations of the physical characteristics of carbonatite melts. Temperature measurements on active carbonatitic lava flows and from carbonatitic lava lakes were carried out during a period of effusive activity in June 1988. Temperatures ranged from 491 degrees to 519 degrees C. The highest temperature, measured from a carbonatitic lava lake, was 544 degrees C. These temperatures are several hundred degrees lower than measurements from any silicate lava. At the observed temperatures, the carbonatite melt had lower viscosities than the most fluid basaltic lavas. The unusually low magmatic temperatures were confirmed with 1-atmosphere melting experiments on natural samples.     

Thermoluminescence of lunar samples

Appreciable natural thermoluminescence with glow curve peaks at about 350 degrees centigrade for lunar fines and breccias and above 400 degrees centigrade for crystalline rocks has been recognized in lunar samples. Plagioclase has been identified as the principal carrier of thermoluminescence, and the diference in peak temperatures indicates compositional or structural differences between the feldspars of the different rock types. The present thermoluminescence in the lunar samples is probably the result of a dynamic equilibrium between acquisition from radiation and loss in the lunar thermal environment. A progressive change in the glow curves of core samples with depth below the surface suggests the use of thermoluminescence disequilibrium to detect surfaces buried by recent surface activity, and it also indicates that the lunar diurnal temperature variation penetrates to at least 10.5 centimeters.     

Summer ice and carbon dioxide

The extent of Antarctic pack ice in the summer, as charted from satellite imagery, decreased by 2.5 million square kilometers between 1973 and 1980. The U.S. Navy and Russian atlases and whaling and research ship reports from the 1930's indicate that summer ice conditions earlier in this century were heavier than the current average. Surface air temperatures along the seasonally shifting belt of melting snow between 55 degrees and 80 degrees N during spring and summer were higher in 1974 to 1978 than in 1934 to 1938. The observed departures in the two hemispheres qualitatively agree with the predicted impact of an increase in atmospheric carbon dioxide. However, since it is not known to, what extent the changes in snow and ice cover and in temperature can be explained by the natural variability of the climate system or by other processes unrelated to carbon dioxide, a cause-and-effect relation cannot yet be established.