Diversity of Comets: Formation Zones and Dynamical Paths

Author: Weissman, P.R.

Source: Space Science Reviews, Volume 90, Number 1, 1 January 1999 , pp. 301-311(11)

Publisher: Springer

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The past dozen years have produced a new paradigm with regard to the source regions of comets in the early solar system. It is now widely recognized that the likely source of the Jupiter-family short-period comets (those with Tisserand parameters, T > 2 and periods, P, generally < 20 years) is the Kuiper belt in the ecliptic plane beyond Neptune. In contrast, the source of the Halley-type and long-period comets (those with T < 2 and P > 20 years) appears to be the Oort cloud. However, the comets in the Oort cloud almost certainly originated elsewhere, since accretion is very inefficient at such large heliocentric distances. New dynamical studies now suggest that the source of the Oort cloud comets is the entire giant planets region from Jupiter to Neptune, rather than primarily the Uranus-Neptune region, as previously thought. Some fraction of the Oort cloud population may even be asteroidal bodies formed inside the orbit of Jupiter. These comets and asteroids underwent a complex dynamical random walk among the giant planets before they were ejected to distant orbits in the Oort cloud, with possible interesting consequences for their thermal and collisional histories. Observational evidence for diversity in cometary compositions is limited, at best.

Keywords: Kuiper belt; Oort cloud; dynamical evolution; formation zones; physical processing

Document Type: Regular Paper

Affiliations: Jet Propulsion Laboratory, Earth and Space Sciences Division, Mail stop 183-601, 4800 Oak Grove Drive, Pasadena, CA 91109 USA

Publication date: January 1, 1999

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