'Definite Evidence' Of Alien Life Within 20-30 Years, NASA Chief Scientist Says

There will be "strong indications" of alien life within a decade and "definite evidence" of it within 20 to 30 years, NASA's chief scientist has said.

"We know where to look. We know how to look," Ellen Stofan said during a panel discussion Tuesday on NASA's search for alien life and habitable worlds. "In most cases, we have the technology, and we're on a path to implementing it."

But she was quick to add: "We are not talking about little green men. We are talking about little microbes."

Her colleague John Grunsfeld, a former astronaut and associate administrator for the agency's Science Mission Directorate, agreed.

"I think we're one generation away in our solar system, whether it's on an icy moon or on Mars, and one generation [away] on a planet around a nearby star," Grunsfeld said at the same discussion.

Jeffery Newmark, NASA's interim director of heliophysics, added: "It's definitely not an if, it's a when."

You can watch the full discussion below:

Scientists have been searching for extraterrestrial life for years. One way, as NPR's Geoff Brumfiel reported last year, was by searching for alien air pollution.

And recent discoveries suggest that several nearby planets — and their moons — could support some form of life. For example, Geoff reported last month, scientists said they thought there was a warm ocean on Saturn's moon Enceladus. NPR's Nell Greenfieldboyce reported last month that NASA scientists confirmed that Jupiter's moon Ganymede has a salty ocean below its surface. Scientists believe that the presence of water is one possible sign of life.