TY - JOUR
T1 - The Oxidation State of the Lower Atmosphere and Surface of Venus
AU - Fegley, Bruce
AU - Zolotov, Mikhail Yu
AU - Lodders, Katharina
N1 - Funding Information:
This work was supported by NASA Grants NAGW-2867 and NAGW-4485 and NATO Outreach CRG 960252. We thank Peter Gierasch for helpful discussions, Vladimir Krasnopolsky, and Tom Donahue for constructive reviews.
PY - 1997/2
Y1 - 1997/2
N2 - We present a comprehensive study of the redox state of the lower atmosphere and surface of Venus. This study constrains the CO concentration and oxygen fugacity at the surface of Venus. It incorporates: (1) gas phase thermochemical equilibrium and kinetic calculations to model the chemistry of the near-surface atmosphere, (2) a reanalysis of the thermodynamics of the CONTRAST experiment on the Venera 13 and 14 landers, (3) carefully selected thermodynamic data to model the stability of magnetite and hematite on the surface of Venus, and (4) the Venera 9 and 10 lander spectral reflectance data presented by Pieters et al. (1986, Science 234, 1379-1383). The results of our work predict that: (1) the CO concentration at 0 km (735 K) is in the range of 3-20 parts per million by volume, (2) the oxygen fugacity (fO2) at 0 km is in the range of 10-217 to 10-20.0 bars, (3) the fO2 of the atmosphere at 0 km is indistinguishable, within the uncertainties of the thermodynamic data, from the magnetite-hematite phase boundary, (4) gas phase thermochemical equilibrium is reached only, if at all, in the lowest levels of the atmosphere below about 0.7 km (730 K), (5) a disequilibrium region which is more oxidizing than predicted by thermochemical equilibrium exists at higher elevations, and (6) hematite forms at higher elevations due to the more oxidizing conditions in the disequilibrium region. Finally, we suggest experimental, observational, and theoretical studies which can be used to test our predictions and to provide a foundation for the design of experiments on future spacecraft lander missions to Venus.
AB - We present a comprehensive study of the redox state of the lower atmosphere and surface of Venus. This study constrains the CO concentration and oxygen fugacity at the surface of Venus. It incorporates: (1) gas phase thermochemical equilibrium and kinetic calculations to model the chemistry of the near-surface atmosphere, (2) a reanalysis of the thermodynamics of the CONTRAST experiment on the Venera 13 and 14 landers, (3) carefully selected thermodynamic data to model the stability of magnetite and hematite on the surface of Venus, and (4) the Venera 9 and 10 lander spectral reflectance data presented by Pieters et al. (1986, Science 234, 1379-1383). The results of our work predict that: (1) the CO concentration at 0 km (735 K) is in the range of 3-20 parts per million by volume, (2) the oxygen fugacity (fO2) at 0 km is in the range of 10-217 to 10-20.0 bars, (3) the fO2 of the atmosphere at 0 km is indistinguishable, within the uncertainties of the thermodynamic data, from the magnetite-hematite phase boundary, (4) gas phase thermochemical equilibrium is reached only, if at all, in the lowest levels of the atmosphere below about 0.7 km (730 K), (5) a disequilibrium region which is more oxidizing than predicted by thermochemical equilibrium exists at higher elevations, and (6) hematite forms at higher elevations due to the more oxidizing conditions in the disequilibrium region. Finally, we suggest experimental, observational, and theoretical studies which can be used to test our predictions and to provide a foundation for the design of experiments on future spacecraft lander missions to Venus.
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U2 - 10.1006/icar.1996.5628
DO - 10.1006/icar.1996.5628
M3 - Article
AN - SCOPUS:0031071113
SN - 0019-1035
VL - 125
SP - 416
EP - 439
JO - Icarus
JF - Icarus
IS - 2
ER -