"NASA is developing its first-ever mission to identify, capture and redirect a near-Earth asteroid to a stable orbit around the moon, where astronauts will explore it in the 2020s, returning with samples." (YouTube/NASA)

NASA's proposed Asteroid Redirect Mission has been buzzing for awhile now, but unfortunately the space agency has gone with their decidedly less sexy plan b: Instead of trying to pull an entire small asteroid into an inflatable container to whip it into orbit around the moon, they're going to retrieve a boulder from a larger asteroid and try to redirect that.

[Read more: NASA's mission improbable]

At a NASA news conference Wednesday, NASA associate administrator Robert Lightfoot announced that the boulders had it.

"This animation illustrates one of two robotic mission concepts under consideration for NASA's Asteroid Redirect Mission. In this concept, the Asteroid Redirect Vehicle descends to the surface of a large asteroid and robotically collects a boulder from its surface. " (NASA)

He explained that this option would allow NASA to design and use technologies that will be better suited to a much-desired mission to Mars. It's true that he and his colleagues hope that the Asteroid Redirect Mission will help protect Earth from any future catastrophic collisions. But frankly, our track record for not getting hit with giant asteroids is pretty good, so it's not surprising that NASA wants to put its dollars into building things we can take to Mars.

[NASA wants to send its scientists to Mars (using holographic glasses)]

"The systems [to capture a whole asteroid] weren’t quite as extensible to what we'd need on our trip to Mars," he explained. The spacecraft should launch in 2020, he said, and should take about two years to reach the target asteroid — tentatively named asteroid 2008 ev5, though NASA won't have to make a final selection until 2019 — where it could spend as long as 400 days.

Once the boulder is secured, the ARV will mechanically push off, or “hop,” from the surface and then use thrusters to ascend from the asteroid’s surface. (NASA)

The choice of option b does make sense. The bigger asteroid is a larger target, and it's going to have lots of boulders to pick from, so it's a safer mission. Instead of hoping that the robotic spacecraft sent up in 2020 can redirect a small asteroid in a single attempt, NASA scientists can breathe easy (well, slightly easier) as a robotic arm detaches and plucks one of any number of boulders away. "We're going to have multiple targets," Lightfoot said, "so that was the better value in my opinion."

[New images from Rosetta reveal the ‘fried ice cream’ surface of a comet]

Now that we're not hauling a whole asteroid out of whack, the really exciting stuff happens in 2025 or so: NASA will send a manned mission up into the moon's orbit on an Orion rocket. Once they've reached the boulder, astronauts will go out on a spacewalk and take samples of it. Sampling an asteroid is great, because these icy, dusty rocks were born very close to the earliest days of our solar system and still contain many of the molecules prevalent at the time. That's why we're looking so closely at comets like the one Rosetta is orbiting.


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