Target Hunting 
NASA’s last few long-range plans for human exploration of the solar system targeted a couple of easy-to-find destinations: the Moon and the planet Mars. But the most recent plan is a little different. It targets a near-Earth asteroid -- a chunk of rock whose orbit comes close to Earth’s orbit around the Sun. Just which asteroid to target, though, hasn’t been specified yet. And in fact, one recent study says that no one has even found a good target.
The study was conducted by a team led by Mikael Granvik of the University of Hawaii.
The team specified several criteria for a “good” target.
It has to be easy to reach and to get home from, for example; if it’s too far away, you can’t get there and back with current rockets. It has to be in an orbit that would allow astronauts to stay for a while. It has to be big enough to easily track, and to have enough surface gravity to keep astronauts from drifting off into space. And it has to be easy to explore, with a fairly smooth surface.
The team analyzed the orbits of all the known big near-Earth asteroids, and found that not a single one meets all of those criteria.
So the team proposed that NASA launch an infrared observatory to hunt for possible targets. It would orbit the Sun at the same distance as Venus, allowing it to scan all the space beyond Earth’s orbit.
But another team says we might not have to go far at all to find such a target. More about that tomorrow.
Script by Damond Benningfield, Copyright 2010