Editing Asteroid belt (section)

===Main-belt comets===
{{Main|Main-belt comet}}
Several otherwise unremarkable bodies in the outer belt show [[comet]]ary activity. Because their orbits cannot be explained through the capture of classical comets,  many of the outer asteroids are thought to be icy, with the ice occasionally exposed to sublimation through small impacts. Main-belt comets may have been a major source of the Earth's oceans because the deuterium-hydrogen ratio is too low for classical comets to have been the principal source.<ref>{{cite web|url=https://www.youtube.com/watch?v=B1W4NTmI5Bk| archive-url=https://ghostarchive.org/varchive/youtube/20211030/B1W4NTmI5Bk| archive-date=2021-10-30|title=Interview with David Jewitt|publisher=YouTube.com|date=2007-01-05|access-date=2011-05-21}}{{cbignore}}</ref>