Water on Venus: New Insights from Tremolite Decomposition

Johnson, Natasha M.

doi:10.1006/icar.2000.6392

Cited by 40 publications

(18 citation statements)

References 27 publications

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“…Present Venus is an extremely dry planet containing very little H 2 O vapor (about 200-300 ppm Hoffman et al 1980;Moroz et al 1979;Johnson and Fegley 2000) in its atmosphere. The analysis of the Pioneer Venus Large-probe Neutral Mass Spectrometer (LNMS) data indicated that Venus' atmosphere is enriched in D over H relative to Earth by a factor of ∼120 ± 40, implying that Venus was once more "wet".…”

Section: Solar Wind Induced Atmosphere Erosion and Water Loss Over Vementioning

confidence: 98%

A Comparative Study of the Influence of the Active Young Sun on the Early Atmospheres of Earth, Venus, and Mars

et al. 2007

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Because the solar radiation and particle environment plays a major role in all atmospheric processes such as ionization, dissociation, heating of the upper atmospheres, and thermal and non-thermal atmospheric loss processes, the long-time evolution of planetary atmospheres and their water inventories can only be understood within the context of the evolving Sun. We compare the effect of solar induced X-ray and EUV (XUV) heating on the upper atmospheres of Earth, Venus and Mars since the time when the Sun arrived at the Zero-Age-Main-Sequence (ZAMS) about 4.6 Gyr ago. We apply a diffusive-gravitational equilibrium and thermal balance model for studying heating of the early thermospheres by photodissociation and ionization processes, due to exothermic chemical reactions and cooling by IR-radiating molecules like CO 2 , NO, OH, etc. Our model simulations result in extended thermospheres for early Earth, Venus and Mars. The exospheric temperatures obtained for all the three planets during this time period lead to diffusion-limited hydrodynamic escape of atomic hydrogen and high Jeans' escape rates for heavier species like H 2 , He, C, N, O, etc. The duration of this blow-off phase for atomic hydrogen depends essentially on the mixing ratios of CO 2 , N 2 and H 2 O in the atmospheres and could last from ∼100 to several hundred million years. Furthermore, we study the efficiency of various non-thermal atmospheric loss processes on Venus and Mars and investigate the possible protecting effect of the early martian magnetosphere against solar wind induced ion pick up Yu.N. Kulikov et al. erosion. We find that the early martian magnetic field could decrease the ion-related nonthermal escape rates by a great amount. It is possible that non-magnetized early Mars could have lost its whole atmosphere due to the combined effect of its extended upper atmosphere and a dense solar wind plasma flow of the young Sun during about 200 Myr after the Sun arrived at the ZAMS. Depending on the solar wind parameters, our model simulations for early Venus show that ion pick up by strong solar wind from a non-magnetized planet could erode up to an equivalent amount of ∼250 bar of O + ions during the first several hundred million years. This accumulated loss corresponds to an equivalent mass of ∼1 terrestrial ocean (TO (1 TO ∼1.39 × 10 24 g or expressed as partial pressure, about 265 bar, which corresponds to ∼2900 m average depth)). Finally, we discuss and compare our findings with the results of preceding studies.

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Section: Solar Wind Induced Atmosphere Erosion and Water Loss Over Vementioning

confidence: 98%

A Comparative Study of the Influence of the Active Young Sun on the Early Atmospheres of Earth, Venus, and Mars

et al. 2007

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“…The five spectral windows can be effectively used to distinguish ferric (hematitite) and ferrous minerals (e.g., the pyroxenes augite and hypersthene; olivine). The hydrous mineral tremolite-thought to be stable on geologic timescales on Venus (Johnson and Fegley, 2000)-also displays a detectable absorption feature in the available near-IR windows. Both wollastonite-a CO 2 buffer mineral thought to be regulating the CO 2 surface pressure (cf.…”

Section: Observations and Analysismentioning

confidence: 98%

“…Recently, tremolite has been identified as a hydrous mineral that can survive decomposition over geologic time in the venusian environment (Johnson and Fegley, 2000). Its identification would serve as compelling evidence that Venus once had much more water than it has today and that the planet then lost most of its water over time.…”

Section: Observations and Analysismentioning

confidence: 99%

Detection of Sub-Micron Radiation from the Surface of Venus by Cassini/VIMS

Baines

Bellucci²,

Bibring³

et al. 2000

Icarus

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“…Those three sets of XRF major element analyses from the surface of Venus all suggest the presence of basaltic rock types along with variable amounts of S, either primary or secondary from atmospheric interactions. The most common models predict that the surface of Venus should be rich in the minerals anhydrite, olivine, pyroxene and wollastonite or the assemblage calcite + quartz, depending on elevation and temperature [e.g., [14][15][16][17]. These models also predict that the iron minerals hematite or magnetite will be present.…”

Section: Samplesmentioning

confidence: 99%