By Joel Achenbach — "It is really an elegant bringing together of our exciting human spaceflight plan, scientific interest, being able to protect our planet, and utilizing the technology we had invested in and were already investing in," said Lori Garver, NASA's deputy administrator.
But the mission is viewed skeptically by many in the space community. At a July gathering of engineers and scientists at the National Academy of Sciences, veteran engineer Gentry Lee expressed doubt that the complicated elements of the mission could come together by 2021 and said the many uncertainties would boost costs.
"I'm trying very, very hard to look at the positive side of this, or what I would call the possible positive side," he said.
"It's basically wishful thinking in a lot of ways — that there's a suitable target, that you can find it in time, that you can actually catch it if you go there and bring it back," said Al Harris, a retired NASA planetary scientist who specializes in asteroids.
"Of course, there's always luck. But how much money do you want to spend on a chance discovery that might have a very low probability?" said Mark Sykes, a planetary scientist who chairs a NASA advisory group on asteroids.
If the target rock isn't scoped out well in advance, it could even turn out, on close inspection, to be something other than a small asteroid — say, a spent Russian rocket casing that's footloose around the sun.
NASA officials understand this and have recently been floating a different scenario, a Plan B. Instead of the robotic spacecraft trying to nab a small, little-understood and potentially unruly rock, the spacecraft could travel to a much larger, already-discovered asteroid and break off a chunk to bring back to lunar orbit, where astronauts would visit it.