The Blurry Line Between Comets and Asteroids

What the evidence has continued to show is that there is no clean dividing line between asteroids and comets, even though the two categories represent genuinely different things in terms of origin and composition. A comet is not a single homogenous body. It is often an aggregated, heterogeneous mass, and within that conglomerate there can be components that are virtually indistinguishable from asteroids, particularly once volatiles have been driven off through repeated passes near the sun. A devolatilized cometary nucleus can end up looking, behaving, and impacting very much like an asteroid would, which means that when you are trying to classify the object responsible for a particular impact event, the categories themselves start to become less useful than the actual physical characteristics of what struck.