Of all the asteroids relatively close to Earth, a space rock called 1999 AO10 is the most attractive candidate for close-up inspection. But getting to it would be both ridiculously expensive and incredibly dangerous. Sending astronauts there and back would take roughly half a year, and potential rescue missions would be impossible. Astronauts would also be exposing their bodies to untold amounts of radiation once they're outside the Earth's magnetic field.
But there could be another way to study asteroids up close. NASA is reportedly considering a new mission proposed by the Keck Institute for Space Studies that would send a robotic spacecraft to grab a small asteroid, tow it back towards Earth, and then park it in the moon's orbit for us to study as we please. New Scientist reports:
The Keck team envisions launching a slow-moving spacecraft, propelled by solar-heated ions, on an Atlas V rocket. The craft would then propel itself out to a target asteroid, probably a small space rock about 7 metres wide. After studying it briefly, the robot would catch the asteroid in a bag measuring about 10 metres by 15 metres and head back towards the moon. Altogether it would take about six to 10 years to deliver the asteroid to lunar orbit.
Asteroids are a keen area of interest for researchers because they contain potentially harvestable valuables like platinum, and perhaps even oxygen, carbon, and hydrogen to fuel our rockets — which would effectively turn asteroids into gas stations for long-distance space travel. In total, the proposed plan would cost $2.6 billion, or just a shade more expensive than the Mars rover team's Curiosity mission.