Comet Elst-Pizarro is a remarkable body in that it displays characteristics of both asteroids and comets http://www.spacedaily.com/reports/Main_Belt_Comets_May_Have_Been_Source_Of_Earths_Water.html Main-Belt Comets May Have Been Source Of Earths Water, Space Daily, Mar 23, (2006)., and is the prototype of main-belt comets. Its orbit keeps it within the asteroid main belt, while it displays a dust tail like a comet while near perihelion.