Planet: Difference between revisions

The Moon, Io, and Europa have compositions similar to the terrestrial planets; the others are made of ice and rock like the dwarf planets, with [[Tethys (moon)|Tethys]] being made of almost pure ice. Europa is often considered an icy planet, though, because its surface ice layer makes it difficult to study its interior.<ref name=planetarysociety/><ref>{{cite book |first=John S. |last=Lewis |date=2004 |title=Physics and Chemistry of the Solar System |page=425 |edition=2nd |publisher=Academic Press |isbn=978-0-12-446744-6}}</ref> Ganymede and Titan are larger than Mercury by radius, and Callisto almost equals it, but all three are much less massive. Mimas is the smallest object generally agreed to be a [[Geophysical definition of planet|geophysical planet]], at about six&nbsp;millionths of Earth's mass, though there are many larger bodies that may not be geophysical planets (e.g. {{dp|Salacia}}).<ref name=Grundy2019/>