COMETS A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z                    HOME ABOUT CATEGORIES SITE MAP COPYRIGHT ADVERTISE CONTACT entire Web this site nucleus (cometary) Artist's impression of a comet's nucleus The central and relatively small part of a comet. It is often described as a "dirty snowball" since it is made up of about 75 percent ices (including frozen water, ammonia and carbon dioxide) and about 25 percent dust and rock. Related entry    • Halley's Comet Related category    • COMETS Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) BACK TO TOP