NASA thinks we will find signs of alien life in as little as 10 years—and "definitive evidence" in about 20. But it won't be the human-hating advanced races we've seen depicted in Hollywood dramas. There's a good chance this alien life will simply turn out to be microbes.

Chief scientist of NASA, Ellen Stofan, made the bold claim while speaking during a panel discussion.

"We know where to look," Stofan said. "We know how to look. In most cases we have the technology and we're on a path to implementing it. And so I think we're definitely on the road."

We've seen environments all over our solar system that suggest microbial life can be supported off-Earth. Mars may have been a hotbed for activity, while Europa, Ganymede, and Enceladus have all shown evidence of environments conducive to these little microorganisms. We don't know for sure that these moons or planets harbor life, but NASA feels these are our best shots.

NASA has some aggressive plans over the next few decades to follow up on its early discoveries, with the ultimate goal of sending humans to Mars. It might not be the paradise of our own blue marble, but the potential for life could solve some major mysteries about what's out there in the universe.

Are we alone? We're closer than ever to figuring that out.