Extrasolar Planets || Impact of Stellar Activity on the Evolution of Planetary Atmospheres and Habitability
✍ Scribed by Dvorak, Rudolf
- Publisher
- Wiley-VCH Verlag GmbH & Co. KGaA
- Year
- 2007
- Weight
- 291 KB
- Category
- Article
- ISBN
- 3527406719
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✦ Synopsis
In order to understand the principles that generated earth's long-time habitable environment, compared with other terrestrial planets like Venus and Mars and possible terrestrial exoplanets, with orbits inside the habitable zones of late-type stars, one has to understand the evolutionary influence of the solar/stellar radiation and particle environment on planetary atmospheres. We show that the spectral type of a host star plays a major role in all atmospheric processes, where the photochemistry and evolution of planetary atmospheres, as well as their planetary water inventories must be studied within the context of the evolving stellar energy and particle fluxes. Only stable and dense enough atmospheres allow water to be liquid over geological time periods and protect the planetary surface from hostile radiation which may eventually result in the evolution of biospheres. It is shown that atmospheric expansion as well as thermal and nonthermal escape processes depend on the evolution of the stellar x-ray and EUV flux, and on the solar/stellar plasma flows. Model calculations indicate that earth-like exoplanets within close-in habitable zones of dwarf stars (< 0.05 AU) which are exposed to coronal mass ejections, may lose atmospheres equivalent to surface pressure values from tens to hundreds of bars, depending on the strength of their magnetic dynamo and absorbed XUV radiation.