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Brossier J, Gilmore MS, Toner K, Stein AJ. Distinct Mineralogy and Age of Individual Lava Flows in Atla Regio, Venus Derived From Magellan Radar Emissivity. JOURNAL OF GEOPHYSICAL RESEARCH. PLANETS 2021; 126:e2020JE006722. [PMID: 33959469 PMCID: PMC8098063 DOI: 10.1029/2020je006722] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Accepted: 02/18/2021] [Indexed: 06/12/2023]
Abstract
NASA's Magellan mission revealed that many Venus highlands exhibit low radar emissivity values at higher altitudes. This phenomenon is ascribed to the presence of minerals having high dielectric constants, produced or stabilized by temperature-dependent chemical weathering between the rocks and the atmosphere. Some large volcanoes on Venus have multiple reductions of radar emissivity at varying altitudes. The authors present morphological maps of major lava flow units at Maat, Ozza, and Sapas montes and compare them to radar emissivity. Sapas has a single reduction in emissivity values at 6,054.6 km, while Maat and Ozza have several reductions at altitudes of 6,052.5-6,056.7 km. Emissivity values are highly spatially correlated to individual lava flows indicating that minerals in the rocks control the emissivity signature. The emissivity patterns at these volcanoes require at least four individual ferroelectric mineral compositions in the rocks that are highly conductive at Curie temperatures of 693-731 K. These temperatures are compatible with chlorapatite and some perovskite oxides. Modeling the minimum volumes of ferroelectrics (10-100s ppm) shows the volume and type of ferroelectric may vary over the lifetime of a single volcano. The modeled volumes of ferroelectrics in Ozza and Sapas are greater than in Maat, consistent with the production of ferroelectrics via weathering over a longer period of time, and supporting the idea that Maat has younger volcanic activity. The stratigraphic relationship of Maat's youngest flows with impact craters may indicate the timeframe of the production of specific ferroelectrics via chemical weathering is over 9-60 Ma.
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Affiliation(s)
- J. Brossier
- Department of Earth and Environmental Sciences, Planetary Sciences Group, Wesleyan University, Middletown, CT, USA
| | - M. S. Gilmore
- Department of Earth and Environmental Sciences, Planetary Sciences Group, Wesleyan University, Middletown, CT, USA
| | - K. Toner
- Department of Earth and Environmental Sciences, Planetary Sciences Group, Wesleyan University, Middletown, CT, USA
| | - A. J. Stein
- Department of Earth and Environmental Sciences, Planetary Sciences Group, Wesleyan University, Middletown, CT, USA
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Brossier J, Gilmore MS. Variations in the radiophysical properties of tesserae and mountain belts on Venus: Classification and mineralogical trends. ICARUS 2021; 355:114161. [PMID: 33688099 PMCID: PMC7939048 DOI: 10.1016/j.icarus.2020.114161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Numerous studies show that major Venus highlands display anomalously high radar reflectivity and low radar emissivity relative to the planetary average. This is thought to be the result of the formation of minerals having high dielectric constants via weathering reactions occurring between the surface and the deep atmosphere in these elevated terrains, where temperatures are lower. These reactions are a function of rock composition, atmospheric composition, and degree of weathering, or age. Here, we examine the Magellan radar emissivity, altimetry and backscatter data for all mapped tesserae and mountain belts on Venus. We characterize and classify each contiguous highland according to its pattern of the variation of radar emissivity with increasing altitude. The highlands can be assigned to 7 distinct patterns of emissivity that correspond to at least 2 discrete types of mineralogy based on the altitude (and temperature) of the emissivity changes from the global average (excursions). The majority of the emissivity changes occur at altitudes above 6053 km (temperature below 726 K). The emissivity signature of the major tesserae of Aphrodite Terra, Beta Regio and Phoebe Regio are consistent with the presence of ferroelectric minerals in their rocks (Curie temperatures of ~700-720 K). Fortuna tesserae and the mountains belts (Maxwell, Freyja, Akna and Danu montes) in Ishtar Terra are consistent with the presence of semiconductor minerals. Some tesserae in Ishtar Terra (Clotho, Itzpapatotl and Jyestha tesserae) lie at altitudes over 6055 but lack the emissivity excursions seen in Fortuna tesserae and the mountains at same altitudes and thus may represent a third type of tessera composition. Finally, the spatial distribution of radar emissivity classes correlates to different geologic settings which may reflect differences in the mantle dynamics. Alternatively, this variability could be ascribed to changes in the atmospheric conditions.
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Affiliation(s)
- Jeremy Brossier
- Department of Earth and Environmental Sciences, Planetary Sciences Group, Wesleyan University, 265 Church St., Middletown, CT 06459, USA
| | - Martha S. Gilmore
- Department of Earth and Environmental Sciences, Planetary Sciences Group, Wesleyan University, 265 Church St., Middletown, CT 06459, USA
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Solomon SC, Head JW. Venus banded terrain: Tectonic models for band formation and their relationship to lithospheric thermal structure. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/jb089ib08p06885] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Mahieux A, Vandaele AC, Robert S, Wilquet V, Drummond R, Montmessin F, Bertaux JL. Densities and temperatures in the Venus mesosphere and lower thermosphere retrieved from SOIR on board Venus Express: Carbon dioxide measurements at the Venus terminator. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/2012je004058] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Abstract
Titan's dense and cold nitrogen atmosphere contains a small amount of methane under conditions at least approaching those at which one or both constituents would condense. The possibility of methane and nitrogen rain clouds and global methane oceans has been discussed widely. From specific features of radio occultation and other Voyager results, however, it is concluded that nitrogen does not condense on Titan and that Titan has neither global methane oceans nor a global cloud of liquid methane droplets. Certain results indirectly support the conjecture that methane does not condense at any location. However, other considerations favor a methane ice haze high in the troposphere, and liquid and solid methane might exist on the surface and as low clouds at polar latitudes.
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Abstract
Observations of thermal radio emission from the surface of Venus, made by the Pioneer Venus radar mapper at a wavelength of 17 centimeters, show variations that are dominated by changes in surface emissivity. The regions of lowest emissivity (0.54 +/- 0.05 for the highland areas of Aphrodite Terra and Theia Mons) correspond closely to regions of high radar reflectivity reported earlier. These results support the inference of inclusions of material with high electrical conductivity in the surface rock of these areas.
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Blamont JE, Young RE, Seiff A, Ragent B, Sagdeev R, Linkin VM, Kerzhanovich VV, Ingersoll AP, Crisp D, Elson LS, Preston RA, Golitsyn GS, Ivanov VN. Implications of the VEGA Balloon Results for Venus Atmospheric Dynamics. Science 2010; 231:1422-5. [PMID: 17748085 DOI: 10.1126/science.231.4744.1422] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Both VEGA balloons encountered vertical winds with typical velocities of 1 to 2 meters per second. These values are consistent with those estimated from mixing length theory of thermal convection. However, small-scale temperature fluctuations for each balloon were sometimes larger than predicted. The approximate 6.5-kelvin difference in temperature consistently seen between VEGA-1 and VEGA-2 is probably due to synoptic or planetary-scale nonaxisymmetric disturbances that propagate westward with respect to the planet. There is also evidence from Doppler data for the existence of solar-fixed nonaxisymmetric motions that may be thermal tides. Surface topography may influence atmospheric motions experienced by the VEGA-2 balloon.
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Lebonnois S, Hourdin F, Eymet V, Crespin A, Fournier R, Forget F. Superrotation of Venus' atmosphere analyzed with a full general circulation model. ACTA ACUST UNITED AC 2010. [DOI: 10.1029/2009je003458] [Citation(s) in RCA: 153] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Tellmann S, Pätzold M, Häusler B, Bird MK, Tyler GL. Structure of the Venus neutral atmosphere as observed by the Radio Science experiment VeRa on Venus Express. ACTA ACUST UNITED AC 2009. [DOI: 10.1029/2008je003204] [Citation(s) in RCA: 138] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Peralta J, Hueso R, Sánchez-Lavega A, Piccioni G, Lanciano O, Drossart P. Characterization of mesoscale gravity waves in the upper and lower clouds of Venus from VEX-VIRTIS images. ACTA ACUST UNITED AC 2008. [DOI: 10.1029/2008je003185] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Schubert G, Bougher SW, Covey CC, Del Genio AD, Grossman AS, Hollingsworth JL, Limaye SS, Young RE. Venus atmosphere dynamics: A continuing enigma. EXPLORING VENUS AS A TERRESTRIAL PLANET 2007. [DOI: 10.1029/176gm07] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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15
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Forbes JM. Wave coupling in terrestrial planetary atmospheres. ACTA ACUST UNITED AC 2002. [DOI: 10.1029/130gm11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
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Oberbeck VR, McKay CP, Scattergood TW, Carle GC, Valentin JR. The role of cometary particle coalescence in chemical evolution. ORIGINS LIFE EVOL B 2001; 19:39-55. [PMID: 11536611 DOI: 10.1007/bf01808286] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Important prebiotic organic compounds might have been transported to Earth in dust or produced in vapor clouds resulting from atmospheric explosions or impacts of comets. These compounds coalesced in the upper atmosphere with particles ejected from craters formed by impacts of large objects. Coalescence during exposure to UV radiation concentrated organic monomers and enhanced formation of oligomers. Continuing coalescence added material to the growing particles and shielded prebiotic compounds from prolonged UV radiation. These particles settled into the lower atmosphere where they were scavenged by rain. Aqueous chemistry and evaporation of raindrops containing nomomers in high temperature regions near the Earth's surface also promoted continued formation of oligomers. Finally, these oligomers were deposited in the oceans where continued prebiotic evolution led to the most primitive cell. Results of our studies suggest that prebiotic chemical evolution may be an inevitable consequence of impacting comets during the late accretion of planets anywhere in the universe if oceans remained on those planetary surfaces.
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Affiliation(s)
- V R Oberbeck
- NASA Ames Research Center, Moffett Field, CA 94035, USA
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Magalhães JA, Schofield JT, Seiff A. Results of the Mars Pathfinder atmospheric structure investigation. ACTA ACUST UNITED AC 1999. [DOI: 10.1029/1998je900041] [Citation(s) in RCA: 122] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Baker RD, Schubert G, Jones PW. High Rayleigh number compressible convection in Venus' atmosphere: Penetration, entrainment, and turbulence. ACTA ACUST UNITED AC 1999. [DOI: 10.1029/1998je900029] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Seiff A, Kirk DB, Knight TCD, Young RE, Mihalov JD, Young LA, Milos FS, Schubert G, Blanchard RC, Atkinson D. Thermal structure of Jupiter's atmosphere near the edge of a 5-μm hot spot in the north equatorial belt. ACTA ACUST UNITED AC 1998. [DOI: 10.1029/98je01766] [Citation(s) in RCA: 250] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Seiff A, Tillman JE, Murphy JR, Schofield JT, Crisp D, Barnes JR, LaBaw C, Mahoney C, Mihalov JD, Wilson GR, Haberle R. The atmosphere structure and meteorology instrument on the Mars Pathfinder lander. ACTA ACUST UNITED AC 1997. [DOI: 10.1029/96je03320] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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23
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Zhang S, Bougher SW, Alexander MJ. The impact of gravity waves on the Venus thermosphere and O2IR nightglow. ACTA ACUST UNITED AC 1996. [DOI: 10.1029/96je02035] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Pettengill GH, Ford PG, Simpson RA. Electrical Properties of the Venus Surface from Bistatic Radar Observations. Science 1996; 272:1628-31. [PMID: 8662473 DOI: 10.1126/science.272.5268.1628] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
A bistatic radar experiment in 1994, involving reception on Earth of a specularly reflected, linearly polarized 13-centimeter-wavelength signal transmitted from the Magellan spacecraft in orbit around Venus, has established that the surface materials viewed at low and intermediate altitudes on Venus have a relative dielectric permittivity of 4.0 ± 0.5. However, bistatic results for the Maxwell Montes highlands imply an electrically lossy surface with an imaginary dielectric permittivity of -i 100 ± 50, probably associated with a specific conductivity of about 13 mhos per meter. Candidates for highlands surface composition include ferroelectrics, a thin frost of elemental tellurium, or a plating of magnetite or pyrites.
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Affiliation(s)
- GH Pettengill
- G. H. Pettengill and P. G. Ford, Center for Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. R. A. Simpson, Center for Radar Astronomy, Stanford University, Stanford, CA 94305, USA
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25
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Suleiman SH, Kolodner MA, Steffes PG. Laboratory measurement of the temperature dependence of gaseous sulfur dioxide (SO2) microwave absorption with application to the Venus atmosphere. ACTA ACUST UNITED AC 1996. [DOI: 10.1029/95je03728] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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26
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Crisp D, Meadows VS, Bézard B, de Bergh C, Maillard JP, Mills FP. Ground-based near-infrared observations of the Venus nightside: 1.27-μm O2(a1Δg) airglow from the upper atmosphere. ACTA ACUST UNITED AC 1996. [DOI: 10.1029/95je03136] [Citation(s) in RCA: 118] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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27
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Abstract
The dominant large-scale pattern in the clouds of Venus has been described as a "gamma" or "Psi" and tentatively identified by earlier workers as a Kelvin wave. A detailed calculation of linear wave modes in the Venus atmosphere verifies this identification. Cloud feedback by infrared heating fluctuations is a plausible excitation mechanism. Modulation of the large-scale pattern by the wave is a possible explanation for the Y. Momentum transfer by the wave could contribute to sustaining the general circulation.
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Solomon SC, Smrekar SE, Bindschadler DL, Grimm RE, Kaula WM, McGill GE, Phillips RJ, Saunders RS, Schubert G, Squyres SW, Stofan ER. Venus tectonics: An overview of Magellan observations. ACTA ACUST UNITED AC 1992. [DOI: 10.1029/92je01418] [Citation(s) in RCA: 231] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Pettengill GH, Ford PG, Wilt RJ. Venus surface radiothermal emission as observed by Magellan. ACTA ACUST UNITED AC 1992. [DOI: 10.1029/92je01356] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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32
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Klose KB, Wood JA, Hashimoto A. Mineral equilibria and the high radar reflectivity of Venus mountaintops. ACTA ACUST UNITED AC 1992. [DOI: 10.1029/92je01865] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Crisp D, McMuldroch S, Stephens SK, Sinton WM, Ragent B, Hodapp KW, Probst RG, Doyle LR, Allen DA, Elias J. Ground-Based Near-Infrared Imaging Observations of Venus During the Galileo Encounter. Science 1991; 253:1538-41. [PMID: 17784098 DOI: 10.1126/science.253.5027.1538] [Citation(s) in RCA: 63] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Near-infrared images of Venus, obtained from a global network of ground-based observatories during January and February 1990, document the morphology and motions of the night-side near-infrared markings before, during, and after the Galileo Venus encounter. A dark cloud extended halfway around the planet at low latitudes (>+/-40 degrees ) and persisted throughout the observing program. It had a rotation period of 5.5 +/- 0.15 days. The remainder of this latitude band was characterized by small-scale (400 to 1000 kilometers) dark and bright markings with rotation periods of 7.4 +/- 1 days. The different rotation periods for the large dark cloud and the smaller markings suggests that they are produced at different altitudes. Mid-latitudes (+/-40 degrees to 60 degrees ) were usually occupied by bright east-west bands. The highest observable latitudes (+/-60 degrees to 70 degrees ) were always dark and featureless, indicating greater cloud opacity. Maps of the water vapor distribution show no evidence for large horizontal gradients in the lower atmosphere of Venus.
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Bell JF, Crisp D, Lucey PG, Ozoroski TA, Sinton WM, Willis SC, Campbell BA. Spectroscopic Observations of Bright and Dark Emission Features on the Night Side of Venus. Science 1991; 252:1293-6. [PMID: 17842954 DOI: 10.1126/science.252.5010.1293] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Near-infrared spectra of a bright and a dark thermal emission feature on the night side of Venus have been obtained from 2.2 to 2.5 micrometers (microm) at a spectral resolution of 1200 to 1500. Both bright and dark features show numerous weak absorption bands produced by CO(2), CO, water vapor, and other gases. The bright feature (hot spot) emits more radiation than the dark feature (cold spot) throughout this spectral region, but the largest contrasts occur between 2.21 and 2.32 microm, where H(2)SO(4) clouds and a weak CO(2) band provide the only known sources of extinction. The contrast decreases by 55 to 65 percent at wavelengths longer than 2.34 microm, where CO, clouds, and water vapor also absorb and scatter upwelling radiation. This contrast reduction may provide direct spectroscopic evidence for horizontal variations in the water vapor concentrations in the Venus atmosphere at levels below the cloud tops.
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Steffes PG, Klein MJ, Jenkins JM. Observations of the microwave emission of Venus from 1.3 to 3.6 cm. ICARUS 1990; 84:83-92. [PMID: 11538401 DOI: 10.1016/0019-1035(90)90159-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Laboratory measurements of Steffes (1986) have suggested that the intensity and shape of the microwave spectrum of Venus might be especially sensitive to the subcloud abundance of constituents such as SO2 and gaseous H2SO4. It was likewise suggested that some variations of the shape of the emission spectrum might occur between 1.5 and 3 cm (10 to 20 GHz), a wavelength range which had previously only been sparsely observed. As a result, coordinated observations of Venus emission were conducted at four wavelengths between 1.35 cm (22.2 GHz) and 3.6 cm (8.42 GHz) using the 43-m NRAO antenna at Green Bank, West Virginia, and the 64-m antenna at NASA's Deep Space Communication Complex, Goldstone, California. In this paper, we report the methodology and results of these observations, and compare the results with other observations and with calculated emission spectra. We conclude that the observed emission spectrum is consistent with an average subcloud abundance of gaseous H2SO4 in equatorial and midlatitude regions which is approximately 5 ppm. It is suggested that additional measurements of atmospheric microwave opacity be made with the Pioneer-Venus Orbiter Radio Occultation experiment to search for temporal and spatial variations in gaseous H2SO4 abundance in the Venus atmosphere. An upper limit for the subcloud abundance of SO2 is also determined.
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Affiliation(s)
- P G Steffes
- School of Electrical Engineering, Georgia Institute of Technology, Atlanta 30332-0250, USA
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36
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Crisp D, Sinton WM, Hodapp KW, Ragent B, Gerbault F, Goebel JH, Probst RG, Allen DA, Pierce K, Stapelfeldt KR. The Nature of the Near-Infrared Features on the Venus Night Side. Science 1989; 246:506-9. [PMID: 17788700 DOI: 10.1126/science.246.4929.506] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Near-infrared images of the Venus night side show bright contrast features that move from east to west, in the direction of the cloud-top atmospheric superrotation. Recently acquired images of the Venus night side along with earlier spectroscopic observations allow identification of the mechanisms that produce these features, their level of formation, and the wind velocities at those levels. The features are detectable only at wavelengths near 1.74 and 2.3 micrometers, in narrow atmospheric windows between the CO(2) and H(2)O bands. The brightest features have brightness temperatures near 480 Kelvin, whereas the darkest features are more than 50 Kelvin cooler. Several factors suggest that this radiation is emitted by hot gases at altitudes below 35 kilometers in the Venus atmosphere. The feature contrasts are produced as this thermal radiation passes through a higher, cooler, atmospheric layer that has horizontal variations in transparency. The 6.5-day east-west rotation period of the features indicates that equatorial wind speeds are near 70 meters per second in this upper layer. Similar wind speeds have been measured by entry probes and balloons at altitudes between 50 and 55 kilometers in the middle cloud layer. The bright features indicate that there are partial clearings in this cloud deck. The presence of these clearings could decrease the efficiency of the atmospheric greenhouse that maintains the high surface temperatures on Venus.
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LeCompte MA, Paxton LJ, Stewart AIF. Analysis and interpretation of observations of airglow at 297 nm in the Venus thermosphere. ACTA ACUST UNITED AC 1989. [DOI: 10.1029/ja094ia01p00208] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Grimm RE, Solomon SC. Viscous relaxation of impact crater relief on Venus: Constraints on crustal thickness and thermal gradient. ACTA ACUST UNITED AC 1988. [DOI: 10.1029/jb093ib10p11911] [Citation(s) in RCA: 90] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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39
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Mayr HG, Harris I, Kasprzak WT, Dube M, Varosi F. Gravity waves in the upper atmosphere of Venus. ACTA ACUST UNITED AC 1988. [DOI: 10.1029/ja093ia10p11247] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Abstract
In June 1985, two instrumented balloons were placed in the atmosphere of Venus as part of the VEGA mission. Each balloon traveled about 30 percent of the way around the planet at a float altitude near 54 kilometers. In situ sensors measured pressure, temperature, vertical wind velocity, cloud particle backscatter, ambient light level, and frequency of lightning. A ground-based network of 20 radio antennas tracked the balloons by very long baseline interferometry (VLBI) techniques to monitor the Venus winds. The history, organization, and principal characteristics of this international balloon experiment are described.
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Linkin VM, Kerzhanovich VV, Lipatov AN, Shurupov AA, Seiff A, Ragent B, Young RE, Ingersoll AP, Crisp D, Elson LS, Preston RA, Blamont JE. Thermal Structure of the Venus Atmosphere in the Middle Cloud Layer. Science 1986; 231:1420-2. [PMID: 17748084 DOI: 10.1126/science.231.4744.1420] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
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.
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42
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Dickinson RE, Bougher SW. Venus mesosphere and thermosphere: 1. Heat budget and thermal structure. ACTA ACUST UNITED AC 1986. [DOI: 10.1029/ja091ia01p00070] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Head JW, Wilson L. Volcanic processes and landforms on Venus: Theory, predictions, and observations. ACTA ACUST UNITED AC 1986. [DOI: 10.1029/jb091ib09p09407] [Citation(s) in RCA: 175] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Hedin AE, Niemann HB, Kasprzak WT, Seiff A. Global empirical model of the Venus thermosphere. ACTA ACUST UNITED AC 1983. [DOI: 10.1029/ja088ia01p00073] [Citation(s) in RCA: 245] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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