Super-Earth discovered

Last April, a Swiss observatory made an amazing find: Gliese 581C, an extrasolar planet with a livable temperature. We've known for 10 years that there are planets outside our solar system, but this planet is something new.

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To give you some perspective, here are the average temperatures of our nearest and dearest planets:

Mercury: 290 F. Venus: 452 F. Earth: 56 F. Mars: -81 F. Jupiter: -238 F.

In comparison, Gliese 581C has an average temperature of 104 F. That's hot, but livable.

So why do we talk of colonizing our barren moon? Why keep sending probes to Mercury and Mars if the only livable planet (that we know of) is outside our solar system?

Here's why: Gliese 581C is 24 light years away. In other words, 24 years at lightspeed (or 10,000 years by current rocket technology). And for all we know the planet was destroyed 24 years ago.

It's fun to imagine, though. Assuming, we find a way to travel much faster and reach the planet within a human lifespan or two, what would it be like to live on Gliese 581C? Click here to find out.

Bottom line: There's no such thing as a replacement Earth.