European Team of Astronomers Say Gliese 581 May be Habitable

[gokuDX7 2,871]

http://www.dailygalaxy.com/my_weblog/2007/12/return-to-earth.html

More than 10 years after the discovery of the first extra-solar planet, a European team of astronomers have confirmed that one of the planets might indeed be located within the habitable zone around the star Gliese 581.

Until a few years ago, most of the newly discovered exo-planets were Jupiter-mass, probably gaseous, planets. Recently, astronomers have announced the discovery of several planets that are potentially much smaller super-Earths with a minimum mass lower than 10 Earth masses.

In April, a European team announced in Astronomy & Astrophysics the discovery of two new planets orbiting the M star Gliese 581 (a red dwarf), with masses of at least 5 and 8 Earth masses. Given their distance to their parent star, these new planets -Gliese 581c and Gliese 581d- were the first ever possible candidates for habitable planets.

The expression “super-Earths”, which is often used to refer to exoplanets in the 2-10 Earth-mass range, might be confusing, as it indeed suggests that these planets are rocky planets that differ from the Earth only by their mass. But Gliese 581 c and d could very well be big icy planets, with a very different composition from the Earth.

Unlike Jupiter-mass giant planets that are mainly gaseous, terrestrial planets are expected to be extremely diverse: some will be dry and airless, while others will have much more water and gases than the Earth. Only the next generation of telescopes will allow us to tell what these new worlds and their atmospheres are made of and to search for possible indications of life on these planets. Early in the next decade, scientists will launch a new kind of telescope, the interferometry space telescope, which uses the interference of light beams to enhance the resolving power of telescopes. However, theoretical investigations are possible today and can be a great help in identifying targets for these future observations.

Two international teams, one led by Franck Selsis and the other by Werner von Bloh investigated the possible habitability of these two super-Earths from two different points of view.compute the properties of a planet’s atmosphere at various distances from the star. If the planet is too close to the star, the water reservoir is vaporized, so Earth-like life forms cannot exist. The outer boundary corresponds to the distance where gaseous CO2 is then unable to produce the strong greenhouse effect required to warm a planetary surface above the freezing point of water. The major uncertainty for the precise location of the habitable zone boundaries comes from clouds that cannot currently be modeled in detail.

W. von Bloh and his colleagues studied a narrower region of the habitable zone where Earth-like photosynthesis is possible. This photosynthetic biomass production depends on the atmospheric CO2 concentration, as much as on the presence of liquid water on the planet. Using a thermal evolution model for the super-Earths, they have computed the sources of atmospheric CO2 (released through ridges and volcanoes) and its sinks (the consumption of gaseous CO2 by weathering processes).

The main aspect of their model is the persistent balance hat exists on Earth between the sink of CO2 in the atmosphere-ocean system and its release through plate-tectonics. In this model, the ability to sustain a photosynthetic biosphere strongly depends on the age of the planet, because a planet that is too old might not be active anymore, that is, would not release enough gaseous CO2. In this case, the planet would no longer be habitable.

Both teams found that, while Gliese 581 c is too close to the star to be habitable, the planet Gliese 581 d might be habitable. However, the environmental conditions on planet d might be too harsh to allow complex life to appear. Planet d is tidally locked, like the Moon in our Earth-Moon system, meaning that one side of the planet is permanently dark. Thus, strong winds may be caused by the temperature difference between the day and night sides of the planet. Since the planet is located at the outer edge of the habitable zone, life forms would have to grow with reduced stellar irradiation and a singularly odd climate.

However, even under these strange conditions, it might still be habitable if its atmosphere is dense enough. In any case, habitable conditions on planet d should be very different from what we encounter on Earth.....

I wonder if we will find any life on it? I can just see them finding the flying monsters from Pitch black on it lol.

[Pchan 5,162]

That's some sweet news ...

[DeathscytheX 9,732]

Its amazing how scientists can tell you everything about these planets just by the color they appear in an electron scope. Too bad we don't have the tech to blast a probe over there in our life time.

They never did mention anything about that military hypersonic test flight after it was announced it was going to happen last may.