Now that the ESA has landed on a comet, NASA wants to do them one better: capture an entire asteroid (or a piece of one) and put it in orbit around the moon in 2019. But the space agency has now said that it's delaying a decision on exactly how the Asteroid Redirect Mission will do that until 2015. Option A involves bagging and capturing an entire meteorite about 30 feet across, while option B would see them landing on larger target, Philae-style, and digging out a boulder-sized chunk (see the video below). In both cases, it will be towed back to the moon and placed in orbit there. Astronauts launching from the upcoming Space Launch System (SLS) in an Orion capsule will then intercept the orbiting meteorite in 2020, retrieve samples and return to Earth.
While you might be thinking "what could possibly go wrong?", the chosen rock would be far too small to harm Earth. Rather, the mission would help scientists figure out how to defend our planet from meteorites, while learning more about their composition and preparing for deep space missions -- specifically, the planned mission to Mars. NASA delayed the decision because the Asteroid Redirect Mission committee is still torn about option B. While it's clearly more complex than option A, NASA also feels it could learn a lot more skills that would help it on a future Mars mission. Either way, the delay in the decision isn't expected to greatly affect the 2019 launch date.