03 February, 1998. The once-clear distinction between comets and asteroids has become somewhat blurred. An asteroid, a solid body with no tail, has been seen coming in from the Oort comet cloud, while some bodies that seem to be asteroids are probably dead comets. The asteroid may have been kicked out of the asteroid belt by Jupiter.

The asteroid Mathilde, recently observed by the NEAR spacecraft, has a very low density, only 1.5 grams per cubic centimeter, the density and its darkness more typical of a comet than a rocky asteroid. It may, however, be a rubble-pile of fused asteroidal debris created in an ancient impact.