A&A 476, 1365-1371 (2007)
The habitability of super-Earths in Gliese 581W. von Bloh1, C. Bounama1, M. Cuntz2, and S. Franck1
1 Potsdam Institute for Climate Impact Research, PO Box 60 12 03, 14412 Potsdam, Germany
2 Department of Physics, University of Texas at Arlington, Box 19059, Arlington, TX 76019, USA
(Received 24 May 2007 / Accepted 27 September 2007)
Aims.The planetary system around the M star Gliese 581 consists of a hot Neptune (Gl 581b) and two super-Earths (Gl 581c and Gl 581d). The habitability of this system with respect to the super-Earths is investigated following a concept that studies the long-term possibility of photosynthetic biomass production on a dynamically active planet.
Methods.A thermal evolution model for a super-Earth is used to calculate the sources and sinks of atmospheric carbon dioxide. The habitable zone is determined by the limits of photosynthetic life on the planetary surface. Models with different ratios of land / ocean coverage are investigated.
Results.The super-Earth Gl 581c is clearly outside the habitable zone, since it is too close to the star. In contrast, Gl 581d is a tidally locked habitable super-Earth near the outer edge of the habitable zone. Despite the adverse conditions on this planet, at least some primitive forms of life may be able to exist on its surface. Therefore, Gl 581d is an interesting target for the planned TPF/Darwin missions to search for biomarkers in planetary atmospheres.
Key words: stars: individual: Gl 581 -- stars: planetary systems -- astrobiology
© ESO 2007