Past and present water budget of Venus

A detailed analysis of Pioneer Venus large-probe neutral mass spectrometer (LNMS) data confirms an earlier report that the abundance of Venus deuterium relative to hydrogen is 2 orders of magnitude larger than that of terrestrial deuterium. These results have recently received confirmation from ground-based spectroscopic observations. The LNMS data can be analyzed to obtain height profiles for hydrogen compounds because of the very different isotopic signatures of Venus hydrogen and terrestrial hydrogen. The mixing ratio for water increases by a factor of 4 between 0 and 10 km to a value of 2.2 times the 36Ar mixing ratio (67 ppm) and drops to 10 ppm above 50 km. Preliminary analysis has not revealed the presence of any hydrogen constituent that can compensate for the decrease in water vapor mixing ratio below 10 km. No combination of gas phase and surface chemistry has been found to account for the strange behavior, and vertical transport alone is not feasible. These results are inexplicable unless they can be interpreted in terms of large-scale temporal and spatial variations (for which other evidence also exists). It is argued that present-day deuterium and hydrogen cannot be in a steady state with stochastic cometary inputs but that these results call for an early Venus endowed with at least 2 orders of magnitude more water above the surface than is presently there. From the isotope ratio measurement alone, however, how the water got there or how much was originally present cannot be discerned.

[1]  K. Hodapp,et al.  Ground-Based Near-Infrared Imaging Observations of Venus During the Galileo Encounter , 1991, Science.

[2]  T V Johnson,et al.  Galileo Infrared Imaging Spectroscopy Measurements at Venus , 1991, Science.

[3]  J. Pollack,et al.  The dark side of Venus: near-infrared images and spectra from the Anglo-Australian observatory. , 1991, Science.

[4]  J. Bell,et al.  Spectroscopic Observations of Bright and Dark Emission Features on the Night Side of Venus , 1991, Science.

[5]  T. Owen,et al.  Deuterium on Venus: Observations From Earth , 1991, Science.

[6]  D. Grinspoon,et al.  Vertical Distribution of Water in the Atmosphere of Venus: A Simple Thermochemical Explanation , 1990, Science.

[7]  David Crisp,et al.  The deep atmosphere of Venus revealed by high-resolution nightside spectra , 1990, Nature.

[8]  J. Kasting,et al.  CLIMATE EVOLUTION ON THE TERRESTRIAL PLANETS , 1989, Origin and Evolution of Planetary and Satellite Atmospheres.

[9]  D. Hunten,et al.  ESCAPE OF ATMOSPHERES AND LOSS OF WATER , 1989, Origin and Evolution of Planetary and Satellite Atmospheres.

[10]  JOHN S. Lewis,et al.  Cometary Water on Venus: Implications of stochastic impacts , 1988 .

[11]  G. Wetherill.  Accumulation of the terrestrial planets and implications concerning lunar origin , 1986 .

[12]  V. Krasnopolsky.  Total injection of water vapor into the Venus atmosphere , 1985 .

[13]  H. Revercomb,et al.  Net Thermal Radiation in the Atmosphere of Venus , 1985 .

[14]  V. I. Moroz,et al.  Composition of the Venus atmosphere below 100 km altitude , 1985 .

[15]  M. McElroy,et al.  Hydrogen on venus: Exospheric distribution and escape , 1984 .

[16]  L. Zasova,et al.  A new interpretation of the Venera 11 spectra of Venus I. The 0.94-μm water band , 1984 .

[17]  T. Ackerman,et al.  Response of Earth's atmosphere to increases in solar flux and implications for loss of water from Venus. , 1984, Icarus.

[18]  J. Kasting,et al.  Loss of Water from Venus. I. Hydrodynamic Escape of Hydrogen , 1983 .

[19]  G. H. Watkins.  The consequences of cometary and asteroidal impacts on the volatile inventories of the terrestrial planets , 1983 .

[20]  D. Hunten,et al.  Nonthermal escape of hydrogen and deuterium from Venus and implications for loss of water , 1982 .

[21]  A. Watson,et al.  Venus Was Wet: A Measurement of the Ratio of Deuterium to Hydrogen , 1982, Science.

[22]  R. Hodges,et al.  Charge exchange in the Venus ionosphere as the source of the hot exospheric hydrogen , 1981 .

[23]  Charles C. Counselman,et al.  Zonal and meridional circulation of the lower atmosphere of Venus determined by radio interferometry , 1980 .

[24]  J. Pollack,et al.  Pioneer Venus gas chromatography of the lower atmosphere of Venus , 1980 .

[25]  J. S. Lewis,et al.  Kinetic inhibition of CO and N2 reduction in the solar nebula , 1980 .

[26]  J. Pollack,et al.  Origin and evolution of planetary atmospheres , 1980 .

[27]  J. Hoffman,et al.  Pioneer Venus Sounder Probe Neutral Gas Mass Spectrometer , 1980, IEEE Transactions on Geoscience and Remote Sensing.

[28]  R. Prinn.  On the possible roles of gaseous sulfur and sulfanes in the atmosphere of Venus , 1979 .

[29]  M. McElroy,et al.  Composition and Structure of the Venus Atmosphere: Results from Pioneer Venus , 1979, Science.

[30]  J. Hoffman,et al.  Pioneer Venus large probe neutral mass spectrometer , 1979 .

[31]  D. Rapp,et al.  Total Cross Sections for Ionization and Attachment in Gases by Electron Impact. I. Positive Ionization , 1965 .

[32]  F. W. Lampe,et al.  Cross Sections for Ionization by Electrons , 1957 .