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 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.

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. "[https://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 ==