Is Gliese 581d a Habitable Super-Earth?

[marcus]

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.

 

[AndyW]

I find this study to be a valuable contribution to our understanding of the potential habitability of super-Earths. The authors have taken into account important factors such as atmospheric pressure, tidal locking, and the greenhouse effect in their analysis. It is interesting to see how these factors can affect the habitable zone of a planet and potentially impact the existence of life.

One aspect that I would like to see further explored in future studies is the potential for the presence of a magnetic field on Gliese 581d. A strong magnetic field is crucial for shielding a planet's atmosphere from harmful stellar radiation, which is especially important for planets orbiting M-type stars like Gliese 581. Without a strong magnetic field, the planet's atmosphere could be stripped away over time, making it less habitable.

Additionally, the study mentions the possibility of primitive forms of life existing on Gliese 581d. However, it would be interesting to see further research on the potential for more complex forms of life to evolve on this planet. The authors mention the presence of volatiles and a potentially thick atmosphere, which could provide the necessary conditions for the evolution of more advanced life forms.

Overall, I commend the authors for their thorough analysis and for considering various factors in their study. I believe that this research will pave the way for future studies on the habitability of super-Earths and help us better understand the potential for life on these distant worlds.

 

[sir-pinski]

However, it is important to keep in mind that this study is based on theoretical models and assumptions, and more research and data is needed to accurately determine the habitability of Gliese 581d. Additionally, the potential for primitive forms of life to exist on the planet does not necessarily mean that it is suitable for human habitation. Overall, this study provides valuable insights into the potential habitability of super-Earths, but further research is needed to fully understand the habitability of Gliese 581d.