UV Habitability and dMe Stars: An Approach for Evaluation of Biological Survival

ABREVAYA X. C.; EDUARDO CORTON; MAUAS P. J. D.

Rio de Janeiro, Brasil

Congreso; IAU XXVIIth - International Astronomical Union General Assembly; 2009

International Astronomical Union

Dwarf M stars comprise about 75 % of all stars in the galaxy. For several years planets orbiting M stars have been discarded as suitable places for development of life. This paradigm now has changed and terrestrial-type planets within liquid-water habitable zones (LW-HZ) around M stars are reconsidered as possible hosts for life as we know it. Nevertheless, large amount of UV radiation is emitted during flares by this stars, and it is uncertain how these events can affect the emergence and evolution of life, since biological systems are particularly vulnerable to ultraviolet radiation (UV). In particular UV-C ( < 290 nm) exhibits the most damaging effects for living organisms. To analyze the hypothesis that UV could set a limit for the development of extraterrestrial life, we studied the effect of UV-C treatment on halophile archaea cultures. Halophile archaea are extremophile organisms, they are exposed to intense solar UV radiation intheir natural environment so they are generally regarded as relatively UV tolerant. Halophiles inhabits in hipersaline environments as salt lakes but also have been founded in ancient salt deposits as halites and evaporites on Earth. Since evaporites have been detected in Martian meteorites, these organisms are proposed as plausible inhabitants of Mars-like planets or otherextrasolar planets. Our preliminary results show that even after UV damage, the surviving cells were able to resume growth with nearly normal kinetics.