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Escape of hydrogen from venus
Science (New York, N.Y.)
|March 26, 1982
Summary
Oxygen ion recombination in Venus' exosphere creates fast oxygen atoms, driving hydrogen escape. This process increases the deuterium-to-hydrogen ratio over time, suggesting a significant past water abundance.
Area of Science:
- Planetary Science
- Atmospheric Chemistry
- Exosphere Dynamics
Background:
- Recombination of O(2)(+) ions is a key process in Venus' upper atmosphere.
- This process generates fast oxygen atoms that can interact with other atmospheric components.
Purpose of the Study:
- To investigate the role of O(2)(+) recombination in hydrogen escape from Venus.
- To analyze the implications for the deuterium-to-hydrogen ratio and past water abundance.
Main Methods:
- Analysis of atmospheric escape mechanisms.
- Modeling of ion-molecule reactions and atomic collisions in the exosphere.
- Interpretation of data from space missions like Pioneer Venus.
Main Results:
- Recombination of O(2)(+) leads to the escape of approximately 10(7) hydrogen atoms/cm²/s.
- Deuterium escape is negligible, causing the D/H ratio to increase over time.
- The observed mass-2 ion by Pioneer Venus is likely D(+), indicating a contemporary D/H ratio of ~10(-2).
Conclusions:
- The high contemporary D/H ratio implies an initial ratio of 5 x 10(-5).
- This suggests an original water (H2O) abundance of at least 800 g/cm² in Venus' early atmosphere.
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