New spacecraft and bigger space telescopes will bring us closer than we've ever been to finding alien life in space beyond our Earth, NASA scientists say.

That goal is closer than most people might think, panelists at a discussion on the search for extraterrestrial life held by NASA in Washington said.

"We believe we're very, very close in terms of technology and science to actually finding the other Earth and our chance to find signs of life on another world," said Sara Seager, a professor of planetary science and physics at the Massachusetts Institute of Technology.

Seager was joined on the discussion panel by some of NASA's premier experts, including the space agency's chief scientist Ellen Stofan and NASA associate administrator, John Grunsfeld, a former astronaut.

"Finding Earth's twin, that's kind of the holy grail," Grunsfeld said.

Also contributing to the discussion was John Mather, the senior project scientist on the James Webb Space Telescope that is expected to launch in 2018 and which will look for evidence of life on nearby exoplanets.

Specifically, it will search for the presence of gases in exoplanet atmospheres that could only be a byproduct of life.

The telescope will consist of 18 hexagonal mirror segments that will work together as one giant 21-foot-wide mirror, the largest ever launched into space.

With that mirror, almost three times as large the mirror in the Hubble Space Telescope, the Webb telescope will be the most powerful ever built, but even it cannot guarantee success, the panelists acknowledged.

"With the James Webb, we have the first capability of finding life on other planets, but we have to get lucky; we have to beat the odds," Seager said.

And the result may take some time, experts said, suggesting the search for extraterrestrial life could be a mult-generational effort possible only with the cooperation of many different nations and their scientific organizations.

"Putting together the partnership that can find Earth 2.0 is a challenge worthy of a great generation," says Webb telescope project scientist Matt Mountain of the Space Telescope Science Institute in Baltimore.

The challenge is something NASA firmly believed is worthwhile, the space agency's head Charles Bolden says.

"Do we believe there is life beyond Earth?" he asked in his introductory remarks at the panel conference. "I would venture to say that most of my colleagues here today say it is improbable that in the limitless vastness of the universe we humans stand alone."