NASA’s fiscal 2014 budget request will include $100 million for a new mission to find a small asteroid, capture it with a robotic spacecraft and bring it into range of human explorers somewhere in the vicinity of the Moon.

Suggested last year by the Keck Institute for Space Studies at the California Institute of Technology, the idea has attracted favor at NASA and the White House Office of Science and Technology Policy. President Obama’s goal of sending astronauts to a near-Earth asteroid by 2025 can’t be done with foreseeable civil-space spending, the thinking goes. But by moving an asteroid to cislunar space — a high lunar orbit or the second Earth-Moon Lagrangian Point (EML2), above the Moon’s far side — it is conceivable that technically the deadline could be met.

The Keck study estimated it would cost about $2.65 billion to bring in a 500,000-kg (1.1 million-lb.) asteroid, using solar-electric propulsion to reach it and a deployable capture bag to enfold a carbonaceous asteroid measuring 7 meters across. Positioned at EML2, the small space rock would be close enough to reach with an Orion crew vehicle launched by a heavy-lift Space Launch System, and would give a crew a real objective for scientific study.

Members of the Keck team that drafted the proposal briefed it to a National Research Council human-spaceflight technical feasibility panel on March 28, noting that the mission would not pose a threat to Earth because the asteroid would have the density of “a dried mudball,” and would come in much more slowly than the slightly larger asteroid that exploded over Chelyabinsk, Russia, in February.

The hardest part, says Paul Dimotakis of Caltech, would be finding a suitable target, since it would be much smaller than the threatening near-Earth objects already being sought. One or more targets may already have been spotted and dismissed as noise by sky-scanning telescope algorithms, he says, and could be pulled out of existing databases with a software rewrite. In addition to size, makeup and spin, prospective targets would need to be on a heliocentric orbit that will return to Earth’s vicinity in the 2020s, to allow time to develop the mission.

The initial NASA request will be divided among the agency’s human exploration, science and space technology directorates to begin advancing technology already in the works.

That hardware and know-how would also be useful in developing a way to push a threatening asteroid off a collision course with Earth if that ever becomes necessary, says former Planetary Society chief Louis Friedman, another member of the Keck team. And it would be useful to private companies that are already developing long-term plans to exploit asteroids with robotic mining for water and metals.

“I certainly do see a role,” says Chris Lewicki, president and chief engineer of Planetary Resources, Inc. Lewicki says a captured asteroid could serve as a “test mine” that would “allow human operators to bridge the gap between current robotic capability and autonomy” and give expert researchers an opportunity to gain field experience.