Should NASA be thinking about sending a manned mission to an asteroid?
This isn't as silly as it might sound. A major factor in landing on another object in space is what is called "delta-v" -- literally the difference in velocities of the two objects. Everything is moving, and if you leave a moving object -- oh, say, the Earth -- and want to land on another, you have to change your velocity enough to zero out the differences in your velocities. That means burning fuel, and that's a precious commodity.
So the best targets are ones that have very little delta-v from the Earth, and many asteroids fit the bill. They may be on similar orbits to the Earth, or there may be one part of the orbit where the asteroid is moving relatively slowly compared to the Earth. So in fact, getting to some asteroids may be easier than getting to the Moon, even if it means a longer trip!
MY old friend Dan Durda, who knows his stuff about such things, was recently interviewed on an Oklahoma TV station about this topic and as usual does a great job talking about it.
As far as a timetable goes... I wonder. We have to wait for the Orion rockets to be able to do this, and the Moon looms large in NASA's schedule. But I think slipping something like this in the docket is just what NASA should be doing. And we may see it happen around the same time we go back to the Moon.