Comets can come from two sources, the Oort Cloud, or the Kuiper Belt. Is there a significant compositional difference between the two?
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asked Nov 12, 2013 at 1:54
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1$\begingroup$ This sounds like a better fit for Astronomy than the subject of "space exploration." $\endgroup$– Robert CartainoCommented Nov 12, 2013 at 13:58
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1 Answer
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A way of looking at this question is to look at the processes that affect comets in these two regions. (Hence, this is a 'part answer')
The reason, according to the article The evolution of comets in the Oort cloud and Kuiper belt, is because recent data and research suggest that the comets in these regions are not pristine examples of the early solar system, to paraphrase the main ideas in the article which relate to compositions:
Comets from the Oort cloud would have some of their supervolatiles lost due to heating from passing stars and supernovae events.
Whereas the more densely packed Kuiper Belt would have more cratering and UV damage, from collisions of relative proximity to the Sun respectively. Specifically for Kuiper belt objects, the authors suggest that
It also now seems inevitable that most comets from the Kuiper belt, although they are constructed of ancient material, cannot themselves be ancient—instead they must be ‘recently’ created chips off larger Kuiper belt objects, formed in violent ($km/s$ class) impacts, rather than the gentle environment required for cometary accretion in the early solar nebula.
Both types would be affected by cosmic rays and dust.
One major conclusion of the article Comet Chemistry: Obtaining Clues to the Formation and Evolution of the Solar System with High-Resolution Infrared Spectroscopy (Dello Russo et al. 2006) is that
Data suggest compositional differences between long-period (Oort cloud) comets and Jupiter-family (mostly Kuiper Belt) comets, with a greater percentage of Jupiter-family comets showing depleted carbon-chain and volatile abundances.
This is based on their assertion that Oort cloud cometary material was originally with the gas giant planets and were expelled outwards, from the article:
Other comets formed in the giant planets region were ejected out to great distances and formed the Oort cloud, a spherical reservoir of comets thousands of astronomical units from the Sun. On the other hand, comets that formed outside the orbit of Neptune are thought to have remained near the plane of the solar system close to their formation region. These comets make up a reservoir known as the Kuiper Belt.