“By 2020, or even a little before that, we’ll know if there are other Earths out there,” states Laurance Doyle, Ph.D. The astrophysicist is part of the NASA Kepler spacecraft science team monitoring 170,000 of the brightest stars in our galactic neighborhood based on the recent discovery of numerous planets around stars other than the Sun. Launched in 2009, they’re watching for a pattern of three small, annual reductions in brightness that would indicate an Earth-sized planet orbiting another star.

“If we don’t find any Earths… then we can say, ‘Wow, Earth is really rare. We need to take care of it,’” says Doyle, who is also a principal investigator at the SETI Institute and president of the nonprofit Planet Quest. If the scientists do find another Earth-like planet, the next step would be to search for signs of biological life by checking to see if free oxygen is present in the atmosphere.

Sources: Principia Purpose and NASA.gov