It sounds almost like a late 90s sci-fi flick: NASA sends a spacecraft to an asteroid, plucks a boulder off its surface with a robotic claw, and brings it back in orbit around the moon. Then, brave astronaut heroes go and study the space rock up closeand bring samples back to Earth.

Except its not a movie: Thats the real-life idea for the Asteroid Redirect Mission, which NASA announced today. Other than simply being an awesome space version of the claw arcade game (you know you really wanted that stuffed Pikachu), the mission will let NASA test technology and practice techniques needed for going to Mars.

The mission, which will cost up to$1.25 billion, is slated to launch in December 2020. It will take about two years to reach the asteroid(the most likely candidate is aquarter-mile-wide rock called 2008 EV5). The spacecraft will spend up to 400 days there, looking for a good boulder. After picking onemaybe around 13 feet in diameterit will bring the rockover to the moon.In 2025, astronauts will fly NASAs still-to-be-built Orion to dock with the asteroid-carrying spacecraft and study the rock up close.

Although the mission would certainly give scientists an up-close opportunity to look at an asteroid, itsmain purpose is as a testing ground for a Mars mission. The spacecraft will test a solar electronic propulsion system, which uses the power from solar panels to pump out charged particles to provide thrust. Its slower than conventional rockets, but a lot more efficient. You cant lug a lot of rocket fuel to Mars.

Overall, the mission gives NASA a chance at practicing precise navigation and maneuvering techniques that theyll need to master for a Mars mission. Such a trip will also require a lot more cargo, so grabbing and maneuvering a big space rock is good practice. Entering lunar orbit and docking with another spacecraft would also be helpful, as the orbit might be a place for a deep-space habitat, a rendezvous point for astronauts to pick up cargo or stop on their way to Mars.

Andyou knew this part was coming, Armageddonfansthe mission might teach NASA something about preventing an asteroid from striking Earth. After grabbing the boulder, the spacecraft will orbit the asteroid. With the added heft from the rock, the spacecraftsextra gravity would nudge the asteroid, creating a slight change in trajectory that NASA could measure from Earth. Were not talking about a large deflection here, says Robert Lightfoot, an associate administrator at NASA. But the idea is that a similar technique could push a threatening asteroid off a collision course with Earth.

NASA chose this mission concept over one that wouldve bagged an entire asteroid. In that plan, the spacecraft wouldve captured the space rockby enclosing it in a giant, flexible container. The claw concept won out because its rendezvous and soft-landing on the asteroid will allow NASA to test and practice more capabilities in preparation for a Mars mission, Lightfoot says. The claw wouldve also given more chances at grabbing a space rock, whereas it was all or nothing with the bag idea. Its a one-shot deal, he says. It is what it is when we get there. But the claw concept offers some choices. Ive got three to five opportunities to pull one of the boulders off, he says. Not bad odds. Better than winning that Pikachu.

Excerpt from:

NASAs Plan to Give the Moon a Moon