Wikipedia:Today's featured article/May 18, 2004

A comet is a relatively small object similar to an asteroid but composed largely of ice. In the Solar System the orbits of comets extend past that of Pluto; of the comets which enter the inner Solar System, most have relatively highly elliptical orbits. Often described as "dirty snowballs", comets are composed largely of frozen carbon dioxide, methane and water with dust and various mineral aggregates mixed in. Comets are thought of as debris leftover from the condensation of a solar nebula. (more...)

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