Most Earth-like planet to date
Solar Voyager : Current Events in Space Exploration

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  nkalanaga

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Posted: 2010-October-01 at 11:21pm | IP Logged Quote nkalanaga

More reasons to favor life:

"Life" doesn't require sunlight.  There could easily be chemosynthetic life in the oceans on both day and night sides.  In fact, the night side would have an advantage, as many red dwarfs are flare stars when young, and the flares wouldn't bother the night side.  Gl 581 seems to be an old star, so that isn't an issue now, but could give the night side a head start.

Gravity wouldn't be an issue for water-dwelling life, or most terrestrial microbes and plants.  Only things that try to stand up off the surface have to worry about it, and there are plenty of ways to accomplish that.  Humans might not comfortable, but there could well be sizable natives. 100 Kg millipedes, anyone?

I do agree that "100% chance of life" is rather optimistic, though, for a world we've never seen!

N Kalanaga
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  pogona

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Posted: 2010-October-02 at 8:26am | IP Logged Quote pogona

yes, but for what we now sunlight is one of the most efficient energy supliers, chemosynthetic life is less eficient, and may end with the nutrients of the water if the nutrients aren't caught from gases of the atmoshpere, of course there could be life, but we can't now in what stage of evolution, what I do think we can expect is to find they work in a similar way as on earth
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  nkalanaga

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Posted: 2010-October-02 at 10:50pm | IP Logged Quote nkalanaga

Most ocean floor chemosynthetic life depends on the geological activity of the world, not the atmosphere.  Being larger than Earth, Gl 581g should have a larger core, and be active longer.  Thus, the ocean floor would be an ideal place of life.  Admittedly, it would also be almost impossible to detect that life, which is why we didn't know about Earth's deep-sea chemosynthesizers until relatively recently. 

You're probably right about shallow water or land life, unless the world is very active (like Io?), which it probably isn't.  So, if we landed there, and there were no photosynthesizers, we probably wouldn't see much, if any, evidence of life. 

Photosynthesis may have started here on the seafloor, as there are photosynthetic organisms around the same deep-sea vents.  Even with no visible light, they manage to collect infrared from the hot rocks and water.  If the same types appeared at Gl 581g, they would be ideally suited to colonozing the shallower water, and ultimately the land, as the sunlight contains a much higher proportion of infrared that Sol's.  Even that doesn't mean an oxygen atmosphere, as there are photosynthesizers that don't release oxygen, but it should produce some type of detectable change in the atmosphere. 

"Advanced life" is another issue entirely.  Multicellular life is a relatively recent development on Earth, and may or may not be as common as "life".  But that's another subject entirely...  The best estimate of Gl 581's age seems to be about 4.3 billion years, so there has been time for advanced life to appear, if life has evolved at the same rate as on Earth, if there's any life at all. 

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  cheatsguy777

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Posted: 2010-November-25 at 9:47pm | IP Logged Quote cheatsguy777

I heard about the system when Gliese 581 C first was discovered, and it seemed like an earth until they found D, which seemed like an earth until they found G. maybe H or J will be even more earthlike than this one!

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