By now, you may have heard about Gliese 581g, a newly discovered extrasolar planet only about 20 light-years from us. What's special about this planet is that it's in the habitable zone (also known as the Goldilocks zone, where water could be liquid) and could possibly support life. It's also a rocky planet with an atmosphere (I haven't seen data on the composition of this) and gravity comparable to Earth's. According to this article on CNN, some scientists think it's a given that there really is life on Gliese 581g. Personally, I think they should confirm first that there really is water on that planet. I haven't seen a report stating that they have detected water on Gliese 581g, so if you've seen one, please provide a link.
(Of course, there may be types of life out there that don't require liquid water, but for purposes of this blog post, let's stick to lifeforms that operate on similar principles to Terran life.)
If there is life on this planet, what would it be like? Let's extrapolate from what we know about this planet so far:
It orbits a red dwarf star which is cooler than our sun but has a much longer life span. I don't know enough about astronomy or physics to state how the light given off by the red dwarf would differ from sunlight, other than to say it would be different. Plants (or plant-like creatures) might have to use a different wavelength of light than they do here. This would mean that they would use some other energy-capturing protein besides chlorophyll, so they might not be green. Also, if the type of light given off by the red dwarf doesn't provide enough energy, life on Gliese 581g might rely on thermal vents or other sources of energy instead.
The planet is tidally locked, with one side always facing its star and the other always facing away. Although the overall temperature of the planet is similar to Earth's (highest average temperature of -12ºC or 10ºF), I don't know what the temperature is on the warm side or what the variation is from equator to pole. Is this planet tilted on its axis? Does it have seasons? Its year is only about 37 Earth days, so seasons would only be a week or so long. Any life on this planet would have to adapt to this short span, suggesting that life might have a shorter life span as well and move at a fast pace.
As you can see, there's still a lot of data missing that would tell us more about what type of life this planet could support. Can anyone think of science fiction books or stories set on a planet orbiting a red dwarf? If so, please share the titles/authors with us. It would be very interesting to see how well science fiction matches science's findings.