A new type of asteroid, or at least a type that's been poorly studied before because of their difficulty to spot-- has been detected in orbits that cross Earth's own. Go HERE for the full article from New Scientist.
Basically, the scientists are guessing that these may to be the remnant cores of dead comets, having long since used up all the ice and other volatiles that made up their visible tails. They reflect less than 5%-10% of the light that strikes them. However, because they absorb so much more, they are able to be spotted much more easily in the infrared spectrum, such as in the photo above (image courtesy of NASA, btw.)
I think its a very cool discovery, considering they're like comet 'ghosts' haunting the space near Earth. As long as none of them hit us, of course.