Abstract
Because there is no necessary connection between the time required to remove the volatile component of a cometary nucleus by solar heating (physical lifetime) and the dynamical lifetime of a comet, it is possible that a comet may evolve into an observable object of asteroidal appearance. Almost all comets have dynamical lifetimes much shorter than their physical lifetimes and in these cases complete loss of volatiles will not occur. Mechanisms do exist, however, whereby a small but significant fraction of comets will have longer dynamical lifetimes, permitting them to evolve first into Jupiter-family short period comets and then into comets with relatively safe decoupled orbits interior to Jupiter’s orbit. Observed Jupiter-family objects of asteroidal appearance (e.g., 1983SA) are much more likely to be of cometary rather than asteroidal origin. “Decoupling” is facilitated by several mechanisms: perturbations by the terrestrial planets, perturbations by Jupiter and the other giant planets (including resonant perturbations) and non-gravitational orbital changes caused by the loss of gas and dust from the comet. The dynamical time scale for decoupling is probably 105–106 years and almost all decoupled comets are likely to be of asteroidal appearance. Once decoupled, the orbits of the resulting Apollo-Amor objects will evolve on a longer (107–108 year) time scale, and the orbital evidence for these objects having originally been comets rather than asteroids will nearly disappear. Statistically, however, a large fraction of the bodies in deep Earth-crossing orbits with semi-major axes ≳ 2.2 AU are likely to be cometary objects in orbits that have not yet diffused into the steady state distribution. For plausible values of the relevant parameters, estimates can be made of the number of cometary Apollo-Amor “asteroids,” the observed number of Earth-crossing active and inactive short period comets, and the production rate of short period comets. These estimates are compatible with other theoretical and observational inferences that suggest the presence of a significant population of Apollo objects that formerly were active comets.
Keywords
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
Preview
Unable to display preview. Download preview PDF.
References
Arnold, J. R. (1965) The origin of meteorites as small bodies. II. The model, III. General considerations, Astrophys. J. 141, 1536–1556.
Campins, H., A’Hearn, M. F., Schleicher, D. G., and Millis, R. L. (1988) The nucleus of comet P/Tempel 2, Bull. Amer. Astron. Soc. 20 (abstract).
Duncan, M., Quinn, T., and Tremaine, S. (1987) The formation and extent of the solar system comet cloud, Astrophys. J. 94, 1330–1338.
Duncan, M., Quinn, T., and Tremaine, S. D. (1988) The origin of short period comets, Astrophys. J. 328, L69–L73.
Everhart, E. (1972) The origin of short period comets, Astrophys. Lett. 10, 131–135.
Everhart, E. (1977) The evolution of comet orbits as perturbed by Uranus and Neptune, in A. H. Delsemme (ed.), Comets, Asteroids, Meteorites University of Toledo, Toledo, pp. 99–104.
Fernández, J. A. (1980) On the existence of a cometary belt beyond Neptune, Mon. Not. Roy. Astron. Soc. 192, 481–491.
Fernández, J. A., and W.-H. Ip (1983) On the time evolution of the cometary influx in the region of the terrestrial planets, Icarus 54, 377–387.
Fernández, J. A. (1985) Dynamical capture and physical decay of short-period comets, Icarus 64, 308–319.
Grieve, R. A. F., and Dence, M. R. (1979) The terrestrial cratering record II. The crater production rate, Icarus 38, 230–242.
Havnes, O. (1967) The effect of repeated close approaches to Jupiter on short-period comets, Icarus 12, 331–337.
Hills, J. G. (1981) Comet showers and the steady-state infall of comets from the Oort cloud, Astron. J. 86, 1730–1740.
Lecar, M., and Franklin, F. A. (1973) On the original distribution of the asteroids, I, Icarus 20, 422–436.
Marsden, B. G. (1985) Nongravitational forces on comets: The first fifteen years, in A. Carusi and G. B. Valsecchi (eds.), Dynamics of Comets: Their Origin and Evolution D. Reidel Publ. Co., Dordrecht, pp. 343–352.
Marsden, B. G. (1986) I.A.U. Catalogue of cometary orbits. Smithsonian Astrophysical Obs., Cambridge, Mass.
Milani, A., Hahn, G., Carpino, M., and Nobili, A. M. (1989) Dynamics of planet-crossing asteroids: Classes of orbital behaviour. Project Spaceguard, Icarus 78, 212–269.
Öpik, E. J. (1951) Collision probabilities with the planets and the distribution of interplanetary matter, Proc. Roy. Irish Acad. 54A, 165–199.
Öpik, E. J. (1961) The survival of comets and cometary material, Astron. J. 66, 381–382.
Öpik, E. J. (1963) Survival of comet nuclei and the asteroids, Advan. Astron. Astrophys. 2, 219–262.
Scholl, H., and Froeschlé, C. H. (1986) The effects of the secular resonances v 16 and v 5 on asteroid orbits, Astron. Astrophys. 170, 134–144.
Sekanina, Z. (1969) Dynamical and evolutionary aspects of gradual deactivation and disintegration of short-period comets, Astron. J. 74, 1223–1234.
Sekanina, Z. (1971) A core-mantle model for cometary nuclei and asteroids of possible cometary origin, in T. Gehreis (ed.), Physical Studies of Minor Planets, NASA SP-267, pp. 423–428.
Shoemaker, E. M. (1977) Astronomically observable crater-forming projectiles, in D. J. Roddy, R. O. Pepin and R. B. Merrill (eds.), Impact and Explosion Cratering Pergamon Press, New York, pp. 617–628.
Shoemaker, E. M., Williams, J. G., Helin, E. F., and Wolfe, R. F. (1979) Earth-crossing asteroids: orbital classes, collision rates with Earth, and origin, in T. Gehreis (ed.), Asteroids, Univ. of Arizona Press, Tucson, pp. 253–282.
Shoemaker, E. M., and Wolfe, R. F. (1984) Evolution of the Uranus-Neptune planetesimal swarm, Lunar Planet. Sci. XV, 780–781.
Stagg, C. R., and Bailey, M. E. (1989) Stochastic capture of short-period comets, Mon. Not. Roy. Astron. Soc. In press.
Torbett, M. V. (1989) Chaotic motion in a comet disk beyond Neptune: The delivery of short-period comets, Preprint.
Weissman, P. R. (1980) Physical loss of long-period comets, Astron. Astrophys. 85, 191–196.
Weissman, P. R. (1986) The Oort cloud and the galaxy, in R. Smoluchowski, J. N. Bahcall and M. S. Matthews (eds.), The Galaxy and the Solar System, Univ. of Arizona Press, Tucson, pp. 204–237.
Weissman, P. R., A’Hearn, M. F., McFadden, L. A., and Rickman, H. (1989) Evolution of comets into asteroids, in press, in R. Binzel, T. Gehrels and M. S. Matthews (eds.), Asteroids II, Univ. of Arizona Press, Tucson.
Weissman, P. R. (1989) The cometary impactor flux at the Earth. Preprint of ms. submitted to Proceedings of the conference on global catastrophes in Earth history, Snowbird, Utah, October 1988. In press.
Wetherill, G. W. (1968a) Dynamical studies of asteroidal and cometary orbits and their relation to the origin of meteorites, in L. H. Ahrens (ed.), Origin and Distribution of the Elements, Pergamon, Oxford, pp. 423–443.
Wetherill, G. W. (1968b) Relationships between orbits and sources of chondritic meteorites, in P. Millman (ed.), Meteorite Research, D. Reidel Publ. Co., Dordrecht, pp. 573–589.
Wetherill, G. W. (1979) Steady-state population of Apollo-Amor objects, Icarus 37, 96–112.
Wetherill, G. W. (1985) Asteroidal source of ordinary chondrites, Meteoritics 20, 1–22.
Wetherill, G. W. (1987) Dynamic relationships between asteroids, meteorites, and Apollo-Amor objects, Phil. Trans. Roy. Soc. of London A323, 323–337.
Wetherill, G. W. (1988) Where do the Apollo objects come from? Icarus 76, 1–18.
Wetherill, G. W. (1989) Cratering of the terrestrial planets by Apollo objects, Meteoritics 24, 15–22.
Wetherill, G. W., and Williams, J. G. (1968) Evaluation of the Apollo asteroids as sources of stone meteorites, J. Geophys. Res. 73, 635–648.
Wetherill, G. W., and Williams, J. G. (1979) Origin of Differentiated Meteorites, in L. H. Ahrens (ed.), Origin and Distribution of the Elements Pergamon, Oxford, pp. 19–31.
Whipple, F. L. (1950) A comet model I. The acceleration of comet Encke, Astrophys. J. 111, 375–394.
Whipple, F. L. (1951) A comet model II. Physical relations for comets and meteors, Astrophys. J. 113, 464–474.
Williams, J. G. (1973) Meteorites from the asteroid belt? (abstract), Eos 54, 233.
Williams, J. G. and Faulkner, J. (1981) The positions of secular resonant surfaces, Icarus 46, 390–399.
Wisdom, J. (1983) Chaotic behavior and the origin of the 3/1 Kirkwood gap, Icarus 56, 51–74.
Wisdom, J. (1985) Meteorites may follow a chaotic route to Earth, Nature 315, 731–733.
Yeomans, D. K. (1988) A new look at cometary nongravitational forces, Bull. Am. Astron. Soc. 20, 841–842.
Author information
Authors and Affiliations
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 1991 Springer Science+Business Media Dordrecht
About this chapter
Cite this chapter
Wetherill, G.W. (1991). End Products of Cometary Evolution: Cometary Origin of Earth-Crossing Bodies of Asteroidal Appearance. In: Newburn, R.L., Neugebauer, M., Rahe, J. (eds) Comets in the Post-Halley Era. Astrophysics and Space Science Library, vol 167. Springer, Dordrecht. https://doi.org/10.1007/978-94-011-3378-4_22
Download citation
DOI: https://doi.org/10.1007/978-94-011-3378-4_22
Publisher Name: Springer, Dordrecht
Print ISBN: 978-94-010-5494-2
Online ISBN: 978-94-011-3378-4
eBook Packages: Springer Book Archive