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Cockell CS, Higgins PM, Johnstone AA. Biologically Available Chemical Energy in the Temperate but Uninhabitable Venusian Cloud Layer: What Do We Want to Know? ASTROBIOLOGY 2021; 21:1224-1236. [PMID: 33470900 DOI: 10.1089/ast.2020.2280] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The cloud layer has been hypothesized to be the most habitable region of Venus. In the lower clouds, both temperature and pressure fall within bounds that support reproduction of microbial life on Earth, although the water activity of the sulfuric acid cloud droplets makes the clouds uninhabitable to known life. In this study, we carried out an analysis of CHNOPS (carbon, hydrogen, nitrogen, oxygen, phosphorus, sulfur) elements and potential redox couples in the cloud layer, and we used a microbial energetic growth model to investigate quantitatively the chemical energy available for microbial growth from methanogenesis, sulfate reduction, and hydrogen oxidation at temperatures between 278 and 350 K. The purpose was to improve knowledge of how far the venusian cloud layer comes from being habitable. Hydrogen oxidation was favorable at all temperatures; however, negative Gibbs free energies for sulfate reduction and methanogenesis depended critically on the assumed concentrations of electron donors, acceptors, and products. Improved measurements and the investigation of new molecules will allow us to better assess quantitatively how far Venus comes from possessing a habitable cloud layer and what would need to be different to make it habitable. We identify specific required measurements. These data will advance our understanding of the habitability of planetary atmospheres on extrasolar greenhouse worlds and the habitability of Earth when the planet eventually enters a greenhouse state.
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Affiliation(s)
- Charles S Cockell
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom
| | - Peter M Higgins
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom
- Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK
| | - Andrew A Johnstone
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom
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Abstract
Astrobiology is focused on the study of life in the universe. However, lifeless planetary environments yield biological information on the variety of ways in which physical and chemical conditions in the universe preclude the possibility of the origin or persistence of life, and in turn this will help explain the distribution and abundance of life, or lack of it, in the universe. Furthermore, many places that humans wish to explore and settle in space are lifeless, and studying the fate of life in these environments will aid our own success in thriving in them. In this synthetic review, I have three objectives, as follows: (1) To discuss the biological value and use of lifeless environments, (2) To explore the diverse planetary bodies and environments that can be lifeless and to categorize them, and (3) To propose sets of biological experiments that can be undertaken in different categories of lifeless worlds and environments and suggest concepts for mission ideas to realize these goals. They include origin of life and microbial inoculation experiments in lifeless but habitable environments. I suggest that the biological study of lifelessness is an underappreciated area in planetary sciences.
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Affiliation(s)
- Charles S Cockell
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK
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McGouldrick K. Effects of variation in coagulation and photochemistry parameters on the particle size distributions in the Venus clouds. EARTH, PLANETS, AND SPACE : EPS 2017; 69:161. [PMID: 31997914 PMCID: PMC6956946 DOI: 10.1186/s40623-017-0744-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/04/2017] [Accepted: 11/14/2017] [Indexed: 06/10/2023]
Abstract
This paper explores the effects that variation in the coalescence efficiency of the Venus cloud particles can have on the structure of the Venus cloud. It is motivated by the acknowledgment of uncertainties in the measured parameters-and the assumptions made to account for them-that define our present knowledge of the particle characteristics. Specifically, we explore the consequence of allowing the coalescence efficiency of supercooled sulfuric acid in the upper clouds to tend to zero. This produces a cloud that occasionally exhibits an enhancement of small particles at altitude (similar to the upper hazes observed by Pioneer Venus and subsequently shown to be somewhat transient). This simulated cloud occasionally exhibits a rapid growth of particle size near cloud base, exhibiting characteristics similar to those seen in the controversial Mode 3 particles. These results demonstrate that a subset of the variations observed as near-infrared opacity variations in the lower and middle clouds of Venus can be explained by microphysical, in addition to dynamical, variations. Furthermore, the existence of a population of particles exhibiting less efficient coalescence efficiencies would support the likelihood of conditions suitable for charge exchange, hence lightning, in the Venus clouds. We recommend future laboratory studies on the coalescence properties of sulfuric acid under the range of conditions experienced in the Venus clouds. We also recommend future in situ measurements to better characterize the properties of the cloud particles themselves, especially composition and particle habits (shapes).
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Affiliation(s)
- Kevin McGouldrick
- Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, 3665 Discovery Dr., Boulder, CO 80303 USA
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de Souza Bonfim V, Barbosa de Castilho R, Baptista L, Pilling S. SO 3 formation from the X-ray photolysis of SO 2 astrophysical ice analogues: FTIR spectroscopy and thermodynamic investigations. Phys Chem Chem Phys 2017; 19:26906-26917. [PMID: 28953271 DOI: 10.1039/c7cp03679e] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
In this combined experimental-theoretical work we focus on the physical and chemical changes induced by soft X-rays on sulfur dioxide (SO2) ice at a very low temperature, in an attempt to clarify and quantify its survival and chemical changes in some astrophysical environments. SO2 is an important constituent of some Jupiter moons and has also been observed in ices around protostars. The measurements were performed at the Brazilian Synchrotron Light Source (LNLS/CNPEM), in Campinas, Brazil. The SO2 ice sample (12 K) was exposed to a broadband beam of mainly soft X-rays (6-2000 eV) and in situ analyses were performed by IR spectroscopy. The X-ray photodesorption yield (upper limit) was around 0.25 molecules per photon. The values determined for the effective destruction (SO2) and formation (SO3) cross sections were 2.5 × 10-18 cm2 and 2.1 × 10-18 cm2, respectively. The chemical equilibrium (88% of SO2 and 12% of SO3) was reached after the fluence of 1.6 × 1018 photons cm-2. The SO3 formation channels were studied at the second-order Møller-Plesset perturbation theory (MP2) level, which showed the three most favorable reaction routes (ΔH < -79 kcal mol-1) in simulated SO2 ice: (i) SO + O2 → SO3, (ii) SO2 + O → SO3, and (iii) SO2 + O+ → SO3+ + e- → SO3. The amorphous solid environment effect decreases the reactivity of intermediate species towards SO3 formation, and ionic species are even more affected. The experimentally determined effective cross sections and theoretical reaction channels identified in this work allow us to better understand the chemical evolution of certain sulfur-rich astrophysical environments.
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Affiliation(s)
- Víctor de Souza Bonfim
- Universidade do Vale do Paraíba - UNIVAP/Laboratorio de Astroquimica e Astrobioloiga - LASA, São José dos Campos, SP, Brazil.
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Horinouchi T, Murakami SY, Satoh T, Peralta J, Ogohara K, Kouyama T, Imamura T, Kashimura H, Limaye SS, McGouldrick K, Nakamura M, Sato TM, Sugiyama KI, Takagi M, Watanabe S, Yamada M, Yamazaki A, Young EF. Equatorial jet in the lower to middle cloud layer of Venus revealed by Akatsuki. NATURE GEOSCIENCE 2017; 10:646-651. [PMID: 29887914 PMCID: PMC5990972 DOI: 10.1038/ngeo3016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
The Venusian atmosphere is in a state of superrotation where prevailing westward winds move much faster than the planet's rotation. Venus is covered with thick clouds that extend from about 45 to 70 km altitude, but thermal radiation emitted from the lower atmosphere and the surface on the planet's night-side escapes to space at narrow spectral windows of near-infrared. The radiation can be used to estimate winds by tracking the silhouettes of clouds in the lower and middle cloud regions below about 57 km in altitude. Estimates of wind speeds have ranged from 50 to 70 m/s at low- to mid-latitudes, either nearly constant across latitudes or with winds peaking at mid-latitudes. Here we report the detection of winds at low latitude exceeding 80 m/s using IR2 camera images from the Akatsuki orbiter taken during July and August 2016. The angular speed around the planetary rotation axis peaks near the equator, which we suggest is consistent with an equatorial jet, a feature that has not been observed previously in the Venusian atmosphere. The mechanism producing the jet remains unclear. Our observations reveal variability in the zonal flow in the lower and middle cloud region that may provide new challenges and clues to the dynamics of Venus's atmospheric superrotation.
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Affiliation(s)
- Takeshi Horinouchi
- Faculty of Environmental Earth Science, Hokkaido University, N10W5, Sapporo, Hokkaido 060-0810, Japan
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency
- Corresponding author: Takeshi Horinouchi,
| | - Shin-ya Murakami
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency
| | - Takehiko Satoh
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency
- Department of Space and Astronautical Science, School of Physical Sciences, SOKENDAI
| | - Javier Peralta
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency
| | | | - Toru Kouyama
- Artificial Intelligence Research Center, National Institute of Advanced Industrial Science and Technology
| | - Takeshi Imamura
- Graduate School of Frontier Sciences, the University of Tokyo
| | - Hiroki Kashimura
- Department of Planetology / Center for Planetary Science, Kobe University
| | - Sanjay S. Limaye
- Space Science and Engineering Center, the University of Wisconsin-Madison
| | - Kevin McGouldrick
- Laboratory for Atmospheric and Space Physics, University of Colorado Boulder
| | - Masato Nakamura
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency
| | - Takao M. Sato
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency
| | | | | | | | - Manabu Yamada
- Planetary Exploration Research Center, Chiba Institute of Technology
| | - Atsushi Yamazaki
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency
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Interior and Surface Dynamics of Terrestrial Bodies and their Implications for the Habitability. HABITABILITY OF OTHER PLANETS AND SATELLITES 2013. [DOI: 10.1007/978-94-007-6546-7_12] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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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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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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9
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Eymet V, Fournier R, Dufresne JL, Lebonnois S, Hourdin F, Bullock MA. Net exchange parameterization of thermal infrared radiative transfer in Venus' atmosphere. ACTA ACUST UNITED AC 2009. [DOI: 10.1029/2008je003276] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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10
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McGouldrick K, Baines KH, Momary TW, Grinspoon DH. Venus Express/VIRTIS observations of middle and lower cloud variability and implications for dynamics. ACTA ACUST UNITED AC 2008. [DOI: 10.1029/2008je003113] [Citation(s) in RCA: 9] [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 our continuing quest for knowledge, robots are powerful tools for accessing environments too dangerous or too remote for human exploration. Early systems functioned under close human supervision, effectively limited to executing preprogrammed tasks. However, as exploration moves to regions where communication is ineffective or unviable, robots will need to carry out complex tasks without human supervision. To enable such capabilities, robots are being enhanced by advances ranging from new sensor development to automated mission planning software, distributed robotic control, and more efficient power systems. As robotics technology becomes simultaneously more capable and economically viable, individual robots operated at large expense by teams of experts are increasingly supplemented by teams of robots used cooperatively under minimal human supervision.
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Affiliation(s)
- James G Bellingham
- Monterey Bay Aquarium Research Institute, 7700 Sandholdt Road, Moss Landing, CA 95039, USA.
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12
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Titov DV, Bullock MA, Crisp D, Renno NO, Taylor FW, Zasova LV. Radiation in the atmosphere of Venus. EXPLORING VENUS AS A TERRESTRIAL PLANET 2007. [DOI: 10.1029/176gm08] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
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13
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Geng J, Lunine JI, Atkinson GH. Absolute Intensities and Pressure-Broadening Coefficients of 2-mum CO(2) Absorption Features: Intracavity Laser Spectroscopy. APPLIED OPTICS 2001; 40:2551-2560. [PMID: 18357269 DOI: 10.1364/ao.40.002551] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The high detection sensitivity available from intracavity laser spectroscopy (ILS) is extended into the near infrared by solid-state laser systems operating with relatively narrow (~0.002 mum) bandwidths for three CO(2) absorption features of importance to an understanding of planetary atmospheres. The absolute intensities and pressure-broadening properties of the P(12), P(14), and P(16) lines of the ?-? band (12 degrees 1-00 degrees 0) of CO(2) (at 2.0129, 2.0136, and 2.0143 mum) are measured quantitatively by ILS with a Tm:YAG laser operating near 2.0 mum. The temperature dependencies of these absolute intensities and collisional-broadening parameters for these three CO(2) features are also measured over the 110-300 K range. The 3.0-km equivalent absorption path length available from the ILS Tm:YAG system is used to enhance detection sensitivity by more than a factor of 1.5 x 10(4) while maintaining a physical sample cell path length of ~20 cm. The enhanced detection sensitivity of ILS permits absolute intensities and collisional-broadening parameters to be measured from <1-Torr CO(2) over a series of temperatures, conditions that emulate those found in the atmospheres of Mars, Triton, and Venus.
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14
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BORYSOW MARCINGRUSZKAALEKSANDRA. Computer simulation of the far infrared collision induced absorption spectra of gaseous CO2. Mol Phys 1998. [DOI: 10.1080/002689798168709] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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16
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Meadows VS, Crisp D. Ground-based near-infrared observations of the Venus nightside: The thermal structure and water abundance near the surface. ACTA ACUST UNITED AC 1996. [DOI: 10.1029/95je03567] [Citation(s) in RCA: 249] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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17
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Gruszka M, Borysow A. Spectral moments of collision‐induced absorption of CO2 pairs: The role of the intermolecular potential. J Chem Phys 1994. [DOI: 10.1063/1.467542] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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19
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20
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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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21
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Crisp D, Allen DA, Grinspoon DH, Pollack JB. The dark side of Venus: near-infrared images and spectra from the Anglo-Australian observatory. Science 1991; 253:1263-6. [PMID: 11538493 DOI: 10.1126/science.11538493] [Citation(s) in RCA: 64] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Near-infrared images and spectra of the night side of Venus taken at the Anglo-Australian Telescope during February 1990 reveal four new thermal emission windows at 1.10, 1.18, 1.27, and 1.31 micrometers, in addition to the previously discovered windows at 1.74 and 2.3 micrometers. Images of the Venus night side show similar bright and dark markings in all windows, but their contrast is much lower at short wavelengths. The 1.27-micrometers window includes a bright, high-altitude O2 airglow feature in addition to a thermal contribution from the deep atmosphere. Simulations of the 1.27- and 2.3 micrometers spectra indicate water vapor mixing ratios near 40 +/- 20 parts per million by volume between the surface and the cloud base. No large horizontal gradients in the water vapor mixing ratios were detected at these altitudes.
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Affiliation(s)
- D Crisp
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena 91109, USA
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22
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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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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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Pollack JB, Kasting JF, Richardson SM, Poliakoff K. The case for a wet, warm climate on early Mars. ICARUS 1987; 71:203-224. [PMID: 11539035 DOI: 10.1016/0019-1035(87)90147-3] [Citation(s) in RCA: 144] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Theoretical arguments are presented in support of the idea that Mars possessed a dense CO2 atmosphere and a wet, warm climate early in its history. Calculations with a one-dimensional radiative-convective climate model indicate that CO2 pressures between 1 and 5 bars would have been required to keep the surface temperature above the freezing point of water early in the planet's history. The higher value corresponds to globally and orbitally averaged conditions and a 30% reduction in solar luminosity; the lower value corresponds to conditions at the equator during perihelion at times of high orbital eccentricity and the same reduced solar luminosity. The plausibility of such a CO2 greenhouse is tested by formulating a simple model of the CO2 geochemical cycle on early Mars. By appropriately scaling the rate of silicate weathering on present Earth, we estimate a weathering time constant of the order of several times 10(7) years for early Mars. Thus, a dense atmosphere could have persisted for a geologically significant time period (approximately 10(9) years) only if atmospheric CO2 was being continuously resupplied. The most likely mechanism by which this might have been accomplished is the thermal decomposition of carbonate rocks induced directly and indirectly (through burial) by intense, global-scale volcanism. For plausible values of the early heat flux, the recycling time constant is also of the order of several times 10(7) years. The amount of CO2 dissolved in standing bodies of water was probably small; thus, the total surficial CO2 inventory required to maintain these conditions was approximately 2 to 10 bars. The amount of CO2 in Mars' atmosphere would eventually have dwindled, and the climate cooled, as the planet's internal heat engine ran down. A test for this theory will be provided by spectroscopic searches for carbonates in Mars' crust.
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Affiliation(s)
- J B Pollack
- NASA Ames Research Center, Moffett Field, California 94035, USA
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25
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Kasting JF, Pollack JB. Effects of high CO2 levels on surface temperature and atmospheric oxidation state of the early Earth. JOURNAL OF ATMOSPHERIC CHEMISTRY 1984; 1:403-428. [PMID: 11541984 DOI: 10.1007/bf00053803] [Citation(s) in RCA: 88] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
One-dimensional radiative-convective and photochemical models are used to examine the effects of enhanced CO2 concentrations on the surface temperature of the early Earth and the composition of the prebiotic atmosphere. Carbon dioxide concentrations of the order of 100-1000 times the present level are required to compensate for an expected solar luminosity decrease of 25-30%, if CO2 and H2O were the only greenhouse gases present. The primitive stratosphere was cold and dry, with a maximum H2O volume mixing ratio of 10(-6). The atmospheric oxidation state was controlled by the balance between volcanic emission of reduced gases, photo-stimulated oxidation of dissolved Fe+2 in the oceans, escape of hydrogen to space, and rainout of H2O2 and H2CO. At high CO2 levels, production of hydrogen owing to rainout of H2O2 would have kept the H2 mixing ratio above 2x10(-4) and the ground-level O2 mixing ratio below 10(-11), even if no other sources of hydrogen were present. Increased solar UV fluxes could have led to small changes in the ground-level mixing ratios of both O2 and H2.
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Affiliation(s)
- J F Kasting
- NASA Ames Research Center, Moffett Field, CA 94035, USA
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Kasting JF, Pollack JB, Ackerman TP. Response of Earth's atmosphere to increases in solar flux and implications for loss of water from Venus. ICARUS 1984; 57:335-355. [PMID: 11541985 DOI: 10.1016/0019-1035(84)90122-2] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
A one-dimensional radiative-convective model is used to compute temperature and water vapor profiles as functions of solar flux for an Earth-like atmosphere. The troposphere is assumed to be fully saturated, with a moist adiabatic lapse rate, and changes in cloudiness are neglected. Predicted surface temperatures increase monotonically from -1 to 111 degrees C as the solar flux is increased from 0.81 to 1.45 times its present value. Surface temperatures corresponding to high solar fluxes may be underestimated, however, owing to neglect of H2O continuum absorption outside of the 8- to 12-micrometers window region. These results imply that the surface temperature of a primitive water-rich Venus should have been at least 80-100 degrees C and may have been much higher. The existence of liquid water at the surface depends on poorly known aspects of H2O continuum absorption and on uncertainties concerning relative humidity and cloudiness. In any case, water vapor should have been a major atmospheric constituent at all altitudes, leading to the rapid hydrodynamic escape of hydrogen. The oxygen left behind by this process was presumably consumed by reactions with reduced minerals in the crust. Both the loss of oxygen and the presently observed enrichment of the deuterium-to-hydrogen ratio are most easily explained if oceans of liquid water were initially present.
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Affiliation(s)
- J F Kasting
- Space Science Division, NASA Ames Research Center, Moffett Field, California 94035, USA
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Suomi VE, Sromovsky LA, Revercomb HE. Net radiation in the atmosphere of Venus: Measurements and interpretation. ACTA ACUST UNITED AC 1980. [DOI: 10.1029/ja085ia13p08200] [Citation(s) in RCA: 28] [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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Tomasko MG, Smith PH, Suomi VE, Sromovsky LA, Revercomb HE, Taylor FW, Martonchik DJ, Seiff A, Boese R, Pollack JB, Ingersoll AP, Schubert G, Covey CC. The thermal balance of venus in light of the Pioneer Venus Mission. ACTA ACUST UNITED AC 1980. [DOI: 10.1029/ja085ia13p08187] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Schubert G, Covey C, Genio AD, Elson LS, Keating G, Seiff A, Young RE, Apt J, Counselman CC, Kliore AJ, Limaye SS, Revercomb HE, Sromovsky LA, Suomi VE, Taylor F, Woo R, von Zahn U. Structure and circulation of the Venus atmosphere. ACTA ACUST UNITED AC 1980. [DOI: 10.1029/ja085ia13p08007] [Citation(s) in RCA: 164] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Seiff A, Kirk DB, Young RE, Blanchard RC, Findlay JT, Kelly GM, Sommer SC. Measurements of thermal structure and thermal contrasts in the atmosphere of Venus and related dynamical observations: Results From the four Pioneer Venus Probes. ACTA ACUST UNITED AC 1980. [DOI: 10.1029/ja085ia13p07903] [Citation(s) in RCA: 252] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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