It may be decades before humanity sets foot on Mars, but we're only five years away from sampling the vast stretches of interstellar space beyond our solar system for the first time, researchers say.

NASA's twin unmanned Voyager spacecraft, which were launched in 1977, are streaking toward the edge of the solar system at around 37,000 mph. At that rate, they'll probably pop out of our sun's sphere of influence and into interstellar space by 2016 or so, according to mission scientists.

"They are about to break free of the solar system," Ed Stone, Voyager project scientist at Caltech in Pasadena, Calif., said during a media teleconference April 28. "We are trying to get outside of our bubble, into interstellar space, to directly measure what is there."