http://arxiv.org/abs/0705.3758 The habitability of super-Earths in Gliese 581 W. von Bloh, C. Bounama, M. Cunntz, S. Franck 4 pages, 2 figures, 1 table (Submitted on 25 May 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 biological productivity 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." this study attempted to estimate most probable conditions on Gliese581D which is near the outer border of habitable for the dim reddish primary Because of the planets large mass, several times earth mass, they judged that it would contain a lot of volatiles and would hold its atmosphere so they estimated a surface atm. pressure at least 5X earth normal. the planet is INSIDE the tidal locking radius for the system so it would keep one face always to the primary ("sun") figuring in the greenhouse effect, they decided it would not be too cold for liquid water. I found their analysis interesting and informative, suggesting how earth-mass planets discovered in the future may be analyzed for habitability.