A NASA robot ship will pluck a large boulder off an asteroid and sling it around the moon, becoming an ad hoc destination to prepare for future human missions to Mars, the U.S. space agency said on Wednesday.
The so-called Asteroid Redirect Mission is estimated to cost about $1.25 billion not including launch costs and is targeted for liftoff in December 2020. It would be followed five years later by a human expedition to the space rock, a modification of a plan proposed by President Barack Obama in 2010.
NASA also considered bagging a smaller asteroid and relocating the entire body into a high orbit around the moon.