Changes

== Life span ==

== Life span ==

Comets have remarkably short life spans. Most periodic comets, particularly in Jupiter's family, have life spans of 10,000<ref name=icr>Humphreys, D. Russell. "[http://www.icr.org/article/1842/ ICR Article: Evidence for a Young World]." [[Institute for Creation Research]], n.d. Accessed July 20, 2008</ref> to 12,000 years.<ref name=Brown/> A comet may make a limited number of orbits before all its volatile substances sublimate away, leaving behind an asteroid-like rock. Certain asteroid-like objects, called ''damocloids'', in highly eccentric orbits around the sun might be inactive comets. 21 such objects are known.<ref name=Jewitt/> Some authorities estimate that half of all near-earth [[asteroid]]s are in fact cometary remnants.<ref name=Arnett/>

Comets have remarkably short life spans. Most periodic comets, particularly in Jupiter's family, have life spans of 10,000<ref name=icr>Humphreys, D. Russell. "[http://www.icr.org/article/1842/ ICR Article: Evidence for a Young World]." [[Institute for Creation Research]], n.d. Accessed July 20, 2008</ref> to 12,000 years.<ref name=Brown/> A comet may make a limited number of orbits before all its volatile substances sublimate away, leaving behind an asteroid-like rock. Certain asteroid-like objects, called ''damocloids'', in highly eccentric orbits around the sun might be inactive comets. 21 such objects are known.<ref name=Jewitt/> Some authorities estimate that half of all near-earth [[asteroid]]s are in fact cometary remnants.<ref name=Arnett/> Comets in near circular orbits in the Kuiper belt and in the Oort Clouds however, tend to have much longer lifespans, hypothesized to be well in the millions of years.

== Origin ==

== Origin ==