Atmospheric studies of habitability in the Gliese 581 system

Abstract

The M-type star Gliese 581 is orbited by at least one terrestrial planet candidate in the habitable zone, i.e. GL 581 d. Orbital simulations have shown that additional planets inside the habitable zone of GL 581 would be dynamically stable. Recently, two further planet candidates have been claimed, one of them in the habitable zone. In view of the ongoing search for planets around M stars which is expected to result in numerous detections of potentially habitable Super-Earths, we take the GL 581 system as an example to investigate such planets. In contrast to previous studies of habitability in the GL 581 system, we use a consistent atmospheric model to assess surface conditions and habitability. Furthermore, we perform detailed atmospheric simulations for a much larger subset of potential planetary and atmospheric scenarios than previously considered. A 1D radiative-convective atmosphere model is used to calculate temperature and pressure profiles of model atmospheres, which we assumed to be composed of molecular nitrogen, water, and carbon dioxide. In these calculations, key parameters such as surface pressure and CO2 concentration as well as orbital distance and planetary mass are varied. Results imply that surface temperatures above freezing could be obtained, independent of the here considered atmospheric scenarios, at an orbital distance of 0.117 AU. For an orbital distance of 0.146 AU, CO2 concentrations as low as 10 times the present Earth's value are sufficient to warm the surface above the freezing point of water. At 0.175 AU, only scenarios with CO2 concentrations of 5% and 95% were found to be habitable. Hence, an additional Super-Earth planet in the GL 581 system in the previously determined dynamical stability range would be considered a potentially habitable planet.

5 pages, 4 figures, accepted in Astronomy&Astrophysics

References in corpus (9)

• Habitable planets around the star Gl 581?
• A ground-based transmission spectrum of the super-Earth exoplanet GJ1214b
• Five Planets Orbiting 55 Cancri
• Observational evidence for a metal rich atmosphere on the super-Earth GJ1214b
• Is Gliese 581d habitable? Some constraints from radiative-convective climate modeling
• Warming the early Earth - CO2 reconsidered
• Bayesian re-analysis of the radial velocities of Gliese 581. Evidence in favour of only four planetary companions
• Model Spectra of the First Potentially Habitable Super-Earth - Gl581d
• Habitability of the Goldilocks Planet Gliese 581g: Results from Geodynamic Models

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