50 to 100 Super Earths expected to be discovered in the next five years

Wednesday, December 02, 2009

Space.com has a good article on Super Earths today. Super Earths are a class of planet that have only recently been discovered, and whether they are suitable places for life or not is still a matter of debate. Due to plate tectonics some think for example that only planets with a mass anywhere from 0.5 to 2.5 times Earth should be able to support life, but then again Venus is a good example of a planet just about our size with almost no plate tectonics at all, so with that type of variation it's still hard to tell just what type of planet makes the best candidate for supporting life.

And by the way, theoretically there should be no reason why one of these planets not even orbiting a star (a so-called rogue planet) shouldn't be able to have life either, since a planet without a star would have an easy time retaining a thick atmosphere and plate tectonics would keep the planet warm for long enough for life to develop. In fact, without any nearby asteroids and comets after being thrown out of its solar system there would be no danger to life from these impacts either.



Back to the article: it also contains some speculation on whether habitability of these planets might be a solution to the Fermi Paradox, the fact that even though the universe should technically be teeming with life here and there we have yet to find any evidence of it or be contacted by intelligent life. If Super Earths are the standard by which life develops and we are an exception (without a lucky strike giving us our Moon the climate on Earth would be far too varied for life to exist anywhere but in the ocean), then that would mean that your average planet with life throughout the universe would be based on a planet much larger than ours, and with a fairly heavier gravity. Let's take the famous Gliese 581 c as an example, shown on the right. It has a mass over five times that of Earth, and a surface gravity probably 2.2 times that of ours, and a diameter about 50% greater than ours. 50% may not sound like a big difference but it results in a surface area about 2.2 times that of ours, which is the equivalent of adding on another seven North Americas, plus the water dividing these extra continents. In addition to that, the extra heavy gravity would make space travel much harder to achieve in the beginning, and if life on these planets is water-based then it would also have all that extra area to explore as well. It's possible that perhaps our Earth is just too small an area to keep an inquisitive species like ours interested, whereas other worlds with life on them take that much longer to fully explore.

But then again, this is all just speculation and we still really have no idea what passes for normal even in our tiny corner of the universe. Discover another few thousand planets and we may be able to begin making some tenuous conclusions.

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