THERMALLY DRIVEN ATMOSPHERIC ESCAPE
Accurately determining the escape rate from a planet's atmosphere is critical for determining its evolution. A large amount of Cassini data is now available for Titan's upper atmosphere and a wealth of data is expected within the next decade on escape from Pluto, Mars, and extra-solar planets. Escape can be driven by upward thermal conduction of energy deposited well below the exobase, as well as by nonthermal processes produced by energy deposited in the exobase region. Recent applications of a model for escape driven by upward thermal conduction, called the slow hydrodynamic escape model, have resulted in surprisingly large loss rates for the atmosphere of Titan, Saturn's largest moon. Based on a molecular kinetic simulation of the exobase region, these rates appear to be orders of magnitude too large. Therefore, the slow hydrodynamic model is evaluated here. It is shown that such a model cannot give a reliable description of the atmospheric temperature profile unless it is coupled to a molecular kinetic description of the exobase region. Therefore, the present escape rates for Titan and Pluto must be re-evaluated using the atmospheric model described here.
- OSTI ID:
- 21452906
- Journal Information:
- Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 716; ISSN ASJOAB; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
AMBIENT TEMPERATURE
ATMOSPHERES
ENERGY TRANSFER
EVOLUTION
HEAT TRANSFER
HYDRODYNAMIC MODEL
MARS PLANET
MATHEMATICAL MODELS
PARTICLE MODELS
PLANETS
PLUTO PLANET
SATELLITE ATMOSPHERES
SATURN PLANET
SOLAR SYSTEM EVOLUTION
STATISTICAL MODELS
THERMAL CONDUCTION
THERMODYNAMIC MODEL