The ultraviolet radiation environment of main sequence stars might be a factor in determining the suitability of extrasolar planets for biological evolution and the subsequent radiation of life in exposed habitats. Assuming the validity of the carbon-water chauvinism, the absorbance of DNA in the UV region of the spectrum is used as a theoretical biological dosimeter to elucidate in more detail the photobiological parameter space of anoxic planets orbiting F, G, and K main sequence stars. Planets within the habitable zones of K main sequence stars have particularly favorable UV environments, with biochemically effective irradiances an order of magnitude lower than those believed to have existed on the surface of Archean Earth. Even using the UV shielding and repair habits of present-day terrestrial organisms, the survivability of the photobiological environment of anoxic K star planets can be demonstrated. The biochemically effective irradiances received in the F star radiation environment are more severe, being 6 to 27 times higher than on Archean Earth. Nevertheless, a combination of UV mitigation strategies seen on the present-day Earth suggest that UV radiation is not a constraint on life even in the inner region of the habitable zone. Life in an ocean on an F-star planet could experience a UV radiation regime similar even to that for present-day Earth. These calculations, although limited by our assumptions on the course of biochemical evolution and the UV absorbance of complex extraterrestrial molecules, suggest that life can survive the UV radiation environments of most extrasolar planets. (C) 1999 Academic Press.
|Number of pages||9|
|Publication status||Published - Oct 1999|
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