Venera

Sulfur and H2SO4 detected in the atmosphere of the planet Venus by USSR Venera 8 (subsequently confirmed... 

Venera Z. Latypova Kazan State University, Kazan, Russia... 

Several Soviet Venera and Vega spacecraft landed on the surface of Venus in the early 1980s, and survived for a few minutes before succumbing to the stifling heat. X-ray fluorescence chemical analyses for a number of major elements in surface samples were reported. Chemical and isotopic analyses of the Venus atmosphere were made by Pioneer Venus, Venera, and other orbiters. 

Surkov Yu. A., Barsukov V. L., Moskalyeva L. P., Kharyukova V. P., and Kemurdzhian A. L. (1984) New data on the composition, structure, and properties of Venus rock obtained by Venera 13 and Venera 14. Proc. 15th Lunar Planet. Sci. Conf J. Geophys. Res. 89, 393-402. 

In the early 1970s, Earth-based measurements of the polarization and refractive index of the cloud particles led to their identification as droplets of concentrated (—75% by mass) sulfuric acid (Esposito et al., 1983). Several years later. Barker (1979) discovered SO2 at Venus cloud tops. Almost simultaneously, instmments on the Pioneer Venus and Venera 11-12 missions also observed SO2. 

The Pioneer Venus mission provided the first radar imaging and altimetry of Venus surface from synthetic aperture radar on an orbiting spacecraft. Subsequently, the Venera 15 and 16 orbiters also carried out radar imaging and altimetry of part of Venus northern hemisphere. Orbital spacecraft radar observations of Venus culminated with the very successful Magellan mission in the early 1990s. 

One important point should be emphasized here. This is the paucity of spacecraft data on the chemical composition and thermal structure of Venus lower atmosphere below —22 km altitude (von Zahn et al., 1983). About 80% of Venus atmospheric mass is below this altitude. Furthermore, altitudes of 0-12 km span the region where the atmosphere is interacting with the surface. However, with three exceptions we have no data on the chemical composition of Venus nearsurface atmosphere. First is the older measurements of CO2 and N2 from crude chemical experiments on the Venera 4-6 landers. Second, the water-vapor profile measured by the Pioneer Venus large probe neutral mass spectrometer. Third, the measurements of water-vapor and gaseous sulfur by spectrophotometer experiments on the Venera II-I4 landers. The gas chromatograph and mass spectrometer experiments on... 

June 12, 1967 Venera 4, atm. probe First successful atmospheric probe on Oct. 18, 1967 showed CO2 is major gas see Jastrow and Rasool (1969)... 

Aug. 17, 1970 Venera 7, lander Dec. 15, 1970, first soft landing on Venus, measured atmospheric composition, pressure, and temperature, survived 23 min (Marov, 1972)... 

Mar. 27, 1972 Venera 8, lander July 22, 1972 landing, first analysis of surface K, U, Th measured by -y-ray analysis, survived for 50 min... 

June 14, 1975 Venera 10, orbiter lander Orbit insertion on Oct. 23, 1975, landed Oct. 25, 1975, survived 65 min see references for Venera 9. 

Sep. 14, 1978 Venera 12, flybys probes Venera 12 flyby probe entry Dec. 21, 1978, atmospheric science from 2 probes, no TV or surface analyses (Hunten et al, 1983 Rrasnopolsky 1986, papers in Cosmic Res. 17(5) Sept./Oct. 1979)... 

Oct. 30, 1981 Venera 13, flyby probe Landed March 1, 1982, first color TV images and X-ray fluorescence analyses of surface, survived 127 min... 

June 7, 1983 Venera 16, orbiter Oct. 14, 1983, orbit entry. Radar imaging from N. pole to 30° N, radar altimetry, and atm. spectroscopy expts. (Barsukov et al., 1992 Bougher et al., 1997)... 

Other books of interest include Lewis and Prinn (1984), which emphasizes the use of observational data for understanding the origin, evolution, and present-day chemistry of planetary atmospheres. Krasnopolsky (1986) focuses on chemistry of the atmospheres of Mars and Venus. He also reviews the atmospheric composition, thermal structure, and cloud measurements by the Soviet Venera and Vega missions. Chamberlain and Hunten (1987) is the classic... 

In addition to the gases fisted in Table 3, Earth-based and spacecraft microwave spectroscopy indicates that H2SO4 vapor (with a mixing ratio of several tens of ppmv) is present below the clouds. Sulfur trioxide, as yet unobserved, is also expected to be present below the clouds in equilibrium with H2SO4 vapor. Spectrophotometers on Venera 11-14 found absorption of blue sunlight in Venus lower atmosphere. This is attributed to elemental sulfur vapor with a total mixing ratio (for all aUotropes) of —20 ppbv in Venus lower atmosphere. 

Venus atmosphere is so dry that Earth-based and spacecraft measurements of the water-vapor abundance are extremely difficult. Historically, many of the in situ water-vapor measurements gave values much higher than the actual water-vapor content. However, reliable values are now available from several sources including the Pioneer Venus mass spectrometer, spectrophotometer experiments on Venera 11-14, Earth-based FTIR spectroscopy of Venus lower atmosphere on the nightside, and IR observations during the Galileo and Cassini flybys of Venus. 

A long-standing question is whether or not the water-vapor abundance in Venus lower atmosphere varies with altitude. Initial interpretation of spectrophotometer experiments on the Venera 11-14 spacecraft suggested a monotonic decrease from —200 ppmv at 50 km to —20 ppmv at the... 

Nephelometers, which use scattered light to measure particle size and number density, on Venera 9-11 and Pioneer Venus showed that the cloud layers are composed of three different types of particles. The first type are aerosols of 0.3 p.m diameter (mode-1 particles), which occur in the... 

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