NASA Scientist Believes We're on the Brink of Discovering Aliens

— -- Not only does NASA's chief scientist believe alien life forms likely exist, but she said the space agency knows where to look and could discover signs of extraterrestrial life within the next decade.

Speaking on a panel discussion on Tuesday about water in the universe, NASA's chief scientist Ellen Stofan said she believes the first indications of alien life could come by 2025 -- with more concrete evidence of extraterrestrial life coming in 20 to 30 years.

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

While Stofan predicts mankind is likely not alone in the universe, she said she expects alien life won't be "little green men."

"We are talking about little microbes," she said.

Water is one of the necessary elements in NASA's quest to find habitable planets and life forms beyond Earth. It's been found in surprising places, including the icy moons of Jupiter and Saturn.

By exploring these other worlds, it's only a matter of time before NASA could strike on evidence proving the existence of alien life.