Thermal Escape from Super Earth Atmospheres in the Habitable Zones of M Stars
Abstract
A fundamental question for exoplanet habitability is the long-term stability of the planet's atmosphere. We numerically solve a one-dimensional multi-component hydrodynamic thermosphere/ionosphere model to examine the thermal and chemical responses of the primary CO2 atmospheres of heavy super Earths (6-10 Earth masses) in the habitable zones of typical low-mass M stars to the enhanced soft X-ray and ultraviolet (XUV) fluxes associated with the prolonged high-activity levels of M stars. The results show that such atmospheres are stable against thermal escape, even for M stars XUV enhancements as large as 1000 compared to the present Earth. It is possible that the CO2-dominant atmospheres of super Earths in the habitable zones of M stars could potentially contain modest amount of free oxygen as a result of more efficient atmosphere escape of carbon than oxygen instead of photosynthesis.
- Publication:
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The Astrophysical Journal
- Pub Date:
- September 2009
- DOI:
- 10.1088/0004-637X/703/1/905
- Bibcode:
- 2009ApJ...703..905T
- Keywords:
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- planetary systems;
- planets and satellites: general