By Joel Achenbach — Just about any mission to an asteroid, even a "near-Earth" asteroid (one that's in an orbit that comes close to Earth, as opposed to the asteroids beyond the orbit of Mars, in the Asteroid Belt) would take hundreds of days. But the new Orion capsule can support astronauts for only about three weeks.
NASA, therefore, needed a fallback to the Obama-style asteroid mission. Hence the Asteroid Redirect Mission.
"He said humans to an asteroid," Bolden told The Washington Post. "There are a lot of different ways to do that. There are probably thousands of ways. I think we have come up with the most practical way, given budgetary constraints today. We're bringing the asteroid to us."
Humans have never moved an object out of its natural orbit. Two years ago, engineers and scientists at the Keck Institute for Space Studies in Pasadena, Calif., proposed doing just that with a small asteroid, citing potential scientific interest. The idea caught on in the corridors at NASA.
"It's not as crazy as it seemed at the beginning," said Charles Elachi, the longtime director of NASA's famed Jet Propulsion Laboratory, operated in Pasadena by Caltech. Elachi's people honed the mission and declared it feasible. These are engineers who know what they're doing: Elachi's office is sprinkled with models of spacecraft that landed on Mars, circled Jupiter and Saturn, probed distant moons and zoomed to the edge of interstellar space.
What the laboratory doesn't have is a firm target for the asteroid mission. These objects are small, and appear fleetingly in telescopes, leaving behind minimal information about their size and composition. Without knowing the albedo — the shininess — of the object, it's impossible to know how big it is when that streak of light appears in the telescope.