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1.
Laboratory simulation and tests of the inlet sampling system and columns of the Pioneer Venus gas chromatograph show that the sensitivity to argon is not diminished after the column regeneration step, argon isotopes are not separated, oxygen and sulfur dioxide are not produced in the inlet sampling system from sulfur trioxide, and sulfur trioxide is not formed from sulfur dioxide and oxygen. Comparisons of the volatile inventory of Venus and Earth imply similar efficiencies of early outgassing but a lower efficiency for later outgassing in the case of Venus. The high oxidation state of the Venus atmosphere in the region of cloud formation may prohibit the generation of elemental sulfur particles. 相似文献
2.
Esposito LW 《Science (New York, N.Y.)》1984,223(4640):1072-1074
Pioneer Venus ultraviolet spectra from the first 5 years of operation show a decline (by more than a factor of 10) in sulfur dioxide abundance at the cloud tops and in the amount of submicron haze above the clouds. At the time of the Pioneer Venus encounter, the values for both parameters greatly exceeded earlier upper limits. However, Venus had a similar appearance in the late 1950's, implying the episodic injection of sulfur dioxide possibly caused by episodic volcanism. The amount of haze in the Venus middle atmosphere is about ten times that found in Earth's stratosphere after the most recent major volcanic eruptions, and the thermal energy required for this injection on Venus is greater by about an order of magnitude than the largest of these recent Earth eruptions and about as large as the Krakatoa eruption of 1883. The episodic behavior of sulfur dioxide implies that steady-state models of the chemistry and dynamics of cloud-top regions may be of limited use. 相似文献
3.
Results from the Pioneer Venus sounder probe neutral mass spectrometer indicate that there is no difference in the isotopic ratios of carbon and oxygen between Venus and Earth to within +/- 5 percent. The mixing ratio of nitrogen is 3.5(+3)(-2) percent with an isotopic ratio within 20 percent of that of Earth. The ratio of argon-36 to argon-40 is 85 percent, and the ratio of argon-38 to argon-36 is 20 percent. The mixing ratios of argon-36 and argon-40 are approximately 40 and 50 parts per million, respectively, with an error of about a factor of 2 (mainly toward a lesser amount) resulting from uncertainty in the response of the ion pump to rare gases. Hydrogen chloride cannot account for more than a few percent of the 36 mass peak, and therefore the large excess of primordial argon is a reasonable conclusion. The ratio of neon-20 to argon-36 of 0.5 +/- 0.3 is definitely terrestrial in character rather than solar. These results indicate that there is a large excess of all primordial noble gases on Venus relative to Earth. There appears to be a considerably higher abundance of sulfur compounds below 20 kilometers than in or above the main cloud layer. The 32 and 60 mass peaks show a sharp increase below 22 kilometers, indicating the possible production of sulfur and carbon oxysulfide (COS) at the expense of sulfur dioxide. 相似文献
4.
Ultraviolet spectroscopy of the Venus cloud tops reveals absorption features attributed to sulfur dioxide in the atmosphere above the cloud tops. Measurements of scattered sunlight at 2663 angstroms show evidence for horizontal and vertical inhomogeneities in cloud structure. Images of the planet at SO(2) absorption wavelengths show albedo features similar to those seen at 3650 angstroms from Mariner 10. Airglowv emissions are consistent with an exospheric temperatuire of approximately 275 K, and a night airglows emission has been detected, indicating the precipitation of energy into the dark thermosphere. 相似文献
5.
Hoffman JH Hodges RR McElroy MB Donahue TM Kolpin M 《Science (New York, N.Y.)》1979,203(4382):800-802
Initial examination of data from the neutral mass spectrometer on the Pioneer Venus sounder probe indicates that the abundances of argon-36, argon-38, and neon-20 in the Venus atmosphere are much higher than those of the corresponding gases in Earth's atmosphere, although the abundance of radiogenic argon-40 is apparently similar for both planets. The lower atmosphere of Venus includes significant concentrations of various gaseous sulfur compounds. The inlet leak to the mass spectrometer was temporarily blocked by an apparently liquid component of the Venus clouds during passage through the dense cloud layer. Analysis of gases released during the evaporation of the droplets shows the presence of water vapor to some compound or compounds of sulfur. 相似文献
6.
Data from the Pioneer Venus cloud particle size spectrometer experiment has revealed the Venus cloud system to be a complicated mixture of particles of various chemical composition distinguishable by their multimodal size distributions. The appearance, disappearance, growth, and decay of certain size modes has aided the preliminary identification of both sulfuric acid and free sulfur cloud regions. The discovery of large particles > 30 micrometers, significant particle mass loading, and size spectral features suggest that precipitation is likely produced; a peculiar aerosol structure beneath the lowest cloud layer could be residue from a recent shower. 相似文献
7.
In this report the fluxes measured by the solar flux radiometer (LSFR) of the Pioneer Venus large probe are compared with calculations for model atmospheres. If the large particles of the middle and lower clouds are assumed to be sulfur, strong, short-wavelength absorption results in a net flux profile significantly different from the LSFR net flux measurements. Models in which the smallest particles are assumed to be sulfur gave flux profiles consistent with the measurements if an additional source of absorption is included in the upper cloud. The narrowband data from 0.590 to 0.665 micrometer indicate an absorption optical depth of about 0.05 below the cloud bottom. The broadband data imply that either this absorption extends over a considerable wavelength interval (as might be the case for dust) or that a very strong absorption band lies on one side of the narrowband filter (as suggested by early Venera 11 and Venera 12 reports). Thermal balance calculations based on the measured visible fluxes indicate high surface temperature for reasonable assumptions of cloud opacity and water vapor abundance. The lapse rate becomes convective within the middle cloud. For water mixing ratios of 2.0 x 10(-4) below the clouds we find a subadiabatic region extending from the cloud bottom to altitudes near 35 kilometers. 相似文献
8.
Preliminary results of the nephelometer experiments conducted aboard the large sounder, day, north, and night probes of the Pioneer Venus mission are presented. The vertical structures of the Venus clouds observed simultaneously at each of the four locations from altitudes of from 63 kilometers to the surface are compared, and similarities and differences are noted. Tentative results from attempting to use the data from the nephelometer and cloud particle size spectrometer on the sounder probe to identify the indices of refraction of cloud particles in various regions of the Venus clouds are reported. Finally the nephelometer readings for the day probe during impact on the surface of Venus are presented. 相似文献
9.
Travis LD Coffeen DL Del Genio AD Hansen JE Kawabata K Lacis AA Lane WA Limaye SS Rossow WB Stone PH 《Science (New York, N.Y.)》1979,205(4401):74-76
Ultraviolet images of Venus over a 3-month period show marked evolution of the planetary scale features in the cloud patterns. The dark horizontal Y feature recurs quasi-periodically, at intervals of about 4 days, but it has also been absent for periods of several weeks. Bow-shaped features observed in Pioneer Venus images are farther upstream from the subsolar point than those in Mariner 10 images. 相似文献
10.
Tomasko MG Doose LR Palmer J Holmes A Wolfe W Castillo ND Smith PH 《Science (New York, N.Y.)》1979,203(4382):795-797
The solar flux radiometer aboard the Pioneer Venus large probe operated successfully during its descent through the atmosphere of Venus. Upward, downward, and net fluxes from 0.4 to 1.0 micrometers were obtained at more than 390 levels between 185 millibars (at an altitude of approximately 61 kilometers) and the surface. Fluxes from 0.4 to 1.8 micrometers were also obtained between 185 millibars and about the level at which the pressure was 2 atmospheres. Data from 80 to 185 millibars should be available after additional decoding by the Deep Space Network. Upward and downward intensities in a narrower band from 0.59 to 0.66 micrometers were also obtained throughout the descent in order to constrain cloud properties. The measurements indicate three cloud regions above the 1.3-atmosphere level (at an altitude of approximately 49 kilometers) and a clear atmosphere beneath that level. At the 67 degrees solar zenith of the probe entry site, some 15 watts per square meter are absorbed at the surface by a dark ground, which implies that about 2 percent of the solar energy incident on the planet is absorbed at the ground. 相似文献
11.
The 2.3-gigahertz log-amplitude fluctuations observed in the radio links of the Pioneer Venus entry probes during Venus encounter have been used to study turbulence in the Venus atmosphere. The deduced estimates of the upper bound of structure constant c(n) of the refractive index fluctuations (c(n) less, similar 4 x 10(-8) cm(-(1/3))) are inconsistent with similar entry probe measurements by Veneras 4 to 8 but are consistent with the radio occultation measurements by flyby (Mariners 5 and 10) and orbiting (Venerat 9) spacecraft. The Pioneer Venus measurements therefore provide a resolution of the long-standing order of magnitude discrepancy between these earlier measurements of c(n). 相似文献
12.
Taylor FW Diner DJ Elson LS McCleese DJ Martonchik JV Delderfield J Bradley SP Schofield JT Gille JC Coffey MT 《Science (New York, N.Y.)》1979,205(4401):65-67
Further results from the Venus orbiter radiometric temperature experiment (VORTEX) on the Pioneer orbiter are presented. These are used to characterize the three-dimensional temperature field, the cloud structure, and the dynamics of the 60-to 130-kilometer altitude region of the Venus atmosphere. One of the new discoveries is a "dipole" structure at high latitudes, with two hot spots rotating around the pole, surrounded by banks of cold cloud. 相似文献
13.
Photochemical processes in planetary atmospheres are strongly influenced by catalytic effects of minor constituents. Catalytic cycles in the atmospheres of Earth and Venus are closely related. For example, chlorine oxides (CIOx) act as catalysts in the two atmospheres. On Earth, they serve to convert odd oxygen (atomic oxygen and ozone) to molecular oxygen. On Venus they have a similar effect, but in addition they accelerate the reactions of atomic and molecular oxygen with carbon monoxide. The latter process occurs by a unique combination of CIOx catalysis and sulfur dioxide photosensitization. The mechanism provides an explanation for the very low extent of carbon dioxide decomposition by sunlight in the Venus atmosphere. 相似文献
14.
Backscattering data for the nephelometer experiments conducted aboard the Pioneer Venus mission probes, including data up to the highest altitudes measured by the probes, are presented. A few small signals were detected below the main cloud deck. Ambient radiation was measured at near-ultraviolet and visible wavelengths; the variation of extinction of near-ultraviolet with altitude is inferred. Ambient radiance decreased more rapidly at 530 than at 745 nanometers in the lower atmosphere. 相似文献
15.
Linkin VM Kerzhanovich VV Lipatov AN Shurupov AA Seiff A Ragent B Young RE Ingersoll AP Crisp D Elson LS Preston RA Blamont JE 《Science (New York, N.Y.)》1986,231(4744):1420-1422
Thermal structure measurements obtained by the two VEGA balloons show the Venus middle cloud layer to be generally adiabatic. Temperatures measured by the two balloons at locations roughly symmetric about the equator differed by about 6.5 kelvins at a given pressure. The VEGA-2 temperatures were about 2.5 kelvins cooler and those of VEGA-1 about 4 kelvins warmer than temperatures measured by the Pioneer Venus Large Probe at these levels. Data taken by the VEGA-2 lander as it passed through the middle cloud agreed with those of the VEGA-2 balloon. Study of individual frames of the balloon data suggests the presence of multiple discrete air masses that are internally adiabatic but lie on slightly different adiabats. These adiabats, for a given balloon, can differ in temperature by as much as 1 kelvin at a given pressure. 相似文献
16.
Donahue TM 《Science (New York, N.Y.)》1979,205(4401):41-44
A summary is presented of the scientific results obtained during the first 120 days of the Pioneer Venus orbiter mission and produced by analysis of multiprobe data as of about 1 April 1979. The summary is essentially a guide to the material presented in the reports devoted to Pioneer Venus results in this issue of Science. 相似文献
17.
Colin L 《Science (New York, N.Y.)》1979,203(4382):743-745
This report is an introduction to the accompanying collection of initial results from the successful Pioneer Venus orbiter and mutiprobe missions that encountered Venus on 4 December and 9 December 1978, respectively. The mission features are briefly described and furnish data accumulated over the first 30 days of the mission. 相似文献
18.
Pérez-DE-Tejada H 《Science (New York, N.Y.)》1980,207(4434):981-983
A latitudinal circulation model of solar wind flow in the near wake of Venus is presented. It is shown that solar wind fluxes entering through the polar terminator can be viscously forced to lower latitudes. The resulting motion produces a downstream elongation of the nightside polar ionosphere out to the downstream extension of the middle- and low-latitude ionopause. The geometry suggested by this flow circulation model provides a simple explanation of the ionospheric bulge inferred from the Pioneer Venus observations. 相似文献
19.
An image of the infrared emission from the Earth-facing hemisphere of Venus was obtained at the time the Pioneer Venus probes penetrated the atmosphere. The thermal structure of the atmosphere at the 85-millibar level included regions of rapidly varying polar features, a solar-related postdawn warm area, and a nonsolar-fixed nighttime warm area. The probes succeeded in entering each of these three thermal regions. 相似文献
20.
The multimodal microstructure of the Venus cloud system has been examined. In addition to confirmed H(2)SO(4) droplets and suspected elemental sulfur, a highly concentrated aerosol population has been observed extending above, within, and below the cloud system. These aerosols appear to cycle through the cloud droplets, but can never be removed by the weak precipitation mechanisms present. All cloud particles are likely laced with aerosol contaminants. Sedimentation and decomposition of H(2)SO(4) in the droplets of the lower cloud region contribute more than 7 watts per square meter of heat flux equaling one-fourth of the solar net flux at 50 kilometers. 相似文献