Finding extraterrestrial life-as-we-know-it is an incredibly difficult prospect. For starters, we need not only to find another relatively small rocky planet orbiting around a star that hangs light years away. No, that planet must also orbit in the “Goldilocks Zone”—not too close to its star that any water would be blasted away, but not too far that the surface would be frozen and dead. For all that, we’ve actually found a few promising candidates so far. But now, to make things even more difficult, says Ian Steadman for Wired UK, our theoretical bastion of other-worldly life might also need to have an asteroid belt hanging just a smidgeon further out in its solar system. Here is how the thinking goes:
According to the theory of punctuated equilibrium, evolution goes faster and further when life has to make rapid changes to survive new environments — and few things have as dramatic an effect on the environment as an asteroid impact. If humans evolved thanks to asteroid impacts, intelligent life might need an asteroid belt like our own to provide just the right number of periodic hits to spur evolution on.
The persistent peppering of Earth with small-scale asteroids was an important source of raw resources (water, rare elements). Big asteroids provided just enough of a bumpy ride to give evolution a kick.
In his famous Drake Equation, Frank Drake proposed a means of mathematically calculating the number of other intelligent species in the universe. If an asteroid belt in just the right place is a key feature of finding intelligent life, the number of possibilities the equation yields could shrink. (Check out the BBC‘s interactive Drake Equation calculator.)
In a survey of 520 gas giant exoplanets, says Steadman, scientists found that only 19 of them had the right solar system-setup to mesh with the asteroid-belt hypothesis.
More from Smithsonian.com:
Choose Your Own Alien Adventure – The Drake Equation Gets Interactive
Meet Earth’s New Companion Asteroid