Abstract
The observed frequency of passages of Earth-crossing long-period (LP) comets (P > 200 yr) is about three per year for comets brighter than absolute magnitude H10 ~ 10.5. About one out of six LP comets is estimated to be new, i.e., making its first passage through the inner planetary region. The sample of observed LP comets shows an excess of retrograde orbits that may be accounted for by the shorter dynamical lifetimes of comets on direct orbits due to planetary perturbations. The original semimajor axes of new comets concentrate in the range 7 × 103 ≳ a orig ≳ 4 × 104 AU, which tells us about the region of the Oort cloud where forces other than planetary perturbations act with the greatest efficiency. Yet the distribution of original semimajor axes cannot tell us anything about the existence of a dense inner core of the Oort cloud. Besides planetary perturbations, passing stars, molecular clouds and the galactic tidal force also influence the dynamical evolution of Oort cloud comets. The observed distribution of the aphelion points of near-parabolic comets shows such a dependence on the galactic latitude. Molecular clouds and stars penetrating very deeply in the Oort cloud are found to give rise to major enhancements in the influx rate of new comets, known as comet showers, at average intervals of a few 107 yr.
An important issue to solve concerns how the frequency of comet passages varies with time, in particular as regards to the current level of comet appearances. Should we be passing through a highly intense phase, most aphelia of the incoming Oort comets would concentrate on the sky area where the strong perturber exerted its greatest effect. By contrast, the observed galactic latitude dependence of the aphelia suggests a dominant influence of the vertical galactic tidal force as compared with random strong perturbers. This seems to indicate that the frequency of comet passages is currently at, or near, its quiescent level. Whether intense comet showers are reflected in the impact cratering record is still a debatable issue. A periodicity of ~ 26–30 Myr in the impact cratering rate is quite uncertain, owing to the small size of the sample of well-dated craters and the noise from background impact craters from asteroids.
The family of short-period (SP) comets (orbital periods P < 20 yr) has long been regarded as the dynamical end-state of new comets on low-inclination orbits captured by Jupiter. However, if SP comets came from a spherical population of comets (e.g., incoming new comets), we should expect to find a percentage of them on retrograde orbits, which contradicts the observations. An alternative hypothesis for the origin of most SP comets is that they come from a trans-Neptunian comet belt. Extensive searches aimed at detecting faint slow-moving objects are required to assess the size of the comet population in the outer planetary region. Modeling of the transfer rate of comets from an outer belt to SP orbits gives transient populations between Saturn and Neptune on the order of 106 — 107 bodies. This is roughly comparable to the upper limit set by the most recent searches of outer solar system bodies.
The impact crater production rate of comets, at the present time, can be estimated to be on the order of 10% of the value corresponding to asteroidal impacts. These estimates, however, are subject to large uncertainties in the brightness-mass relation of comets and crater scaling law. The Earth could have received about 2 × 1020 g of cometary material over the last 4 billion years — if the injection rate of new comets remained constant in the time interval. Within the context of H2O inventory, the cometary influx should have rather minor effects. On the other hand, because of the paucity of H2O content in the atmospheres of Venus and Mars, cometary impact could strongly modulate their water contents.
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References
Allen, C.W. (1963) Astrophysical Quantities (second edition), Athlone Press, London, p.155.
Alvarez, L.W., Alvarez, W., Asaro, F., and Miches, H.V. (1980) “Extraterrestrial cause for the Cretaceous-Tertiary extinction,” Science 208, 1095–1108.
Alvarez, W., and Muller, R.A. (1984) “Evidence from crater ages for periodic impacts on the Earth,” Nature 308, 718–720.
Antonov, V.A., and Latyshev, I.N. (1972) “Determination of the form of the Oort cometary cloud as the Hill surface in the galactic field,” in G.A. Chebotarev, E.I. Kazimirchak-Polonskaya and B.G. Marsden (eds.), The Motion, Evolution of Orbits, and Origin of Comets, IAU Symp. No. 45, Reidel, Dordrecht, Springer-Verlag, New York, pp. 341–345.
Bahcall, J.N. (1984) “Self-consistent determination of the total amount of matter near the Sun,” Astrophys. J. 276, 169–181.
Bahcall, J.N., and Soneira, R.M. (1981) “The distribution of stars to V = 16th magnitude near the north galactic pole: Normalization, clustering properties, and counts in various bands,” Astrophys. J. 246, 122–135.
Bailey, M.E. (1983) “The structure and evolution of the Solar System comet cloud,” Mon. Not. Roy. Astron. Soc. 204, 603–633.
Bailey, M.E. (1986) “The near-parabolic flux and the origin of short period comets,” Nature 324, 350–352.
Bailey, M.E., and Stagg, C.R. (1988) “Cratering constraints on the inner Oort cloud; steady-state models,” Mon. Not. Roy. Astron. Soc. 235, 1–32.
Biermann, L. (1978) “Dense interstellar clouds and comets,” in A. Reiz and T. Anderson (eds.), Astronomical Papers Dedicated to Bengt Stromgren, Copenhagen Observatory, p. 327.
Biermann, L., Huebner, W.F., and Lüst, R. (1983) “Aphelion clustering of ‘new’ comets: Star tracks through Oort’s cloud,” Proc. Natl. Acad. Sci. USA 80, 5151–5155.
Bilo, E.H., and van de Hulst, H.C. (1960) “Methods for computing the original orbits of comets,” BuU. Astron. Inst. Neth. 15, 119–127.
Bogart, R.S., and Noerdlinger, P.D. (1982) “On the distribution of orbits among long-period comets,” Astron. J. 87, 911–917.
Byl, J. (1983) “Galactic perturbations on near-parabolic cometary orbits,” Moon and Planets 29, 121–137.
Cameron, A.G.W. (1962) “The formation of the Sun and the planets,” Icarus 1, 13–69.
Carusi, A., Kresák, L., Perozzi, E., and Valsecchi, G.B. (1984) Long-Term Evolution of Short-Period Comets, Instituto Astrofísical Spaziale Internal Report 12 Rome.
Chebotarev, G.A. (1966) “Cometary motion in the outer solar system,” Soviet Astron. AJ 10, 341–344.
Chyba, C.F. (1987) “The cometary contribution to the oceans of primitive Earth,” Nature 330, 632–635.
Cowan, J.J., and A’Hearn, M.F. (1979) “Vaporization of comet nuclei: Light curves and life times,” Moon and Planets 21, 155–171.
Davis, M., Hut, P., and Muller, R.A. (1984) “Extinction of species by periodic comet showers,” Nature 308, 715–717.
Delsemme, A.H. (1973) “Origin of the short-period comets,” Astron Astrophys. 29, 377–381.
Delsemme, A.H. (1986) “Cometary evidence for a solar companion?,” in R. Smoluchowski, J.N. Bahcall, and M.S. Matthews (eds.), The Galaxy and the Solar System, Univ. of Arizona Press, Tucson, pp. 173–203.
Delemme, A.H. (1989) “Whence come comets?,” Sky & Telesc. March, 260–264.
Delemme, A.H., and Patmiou, M. (1986) “Galactic tides affect the Oort cloud: An observational confirmation,” in Proc. 20th ESLAB Symp. on the Exploration of Halley’s Comet, Heidelberg, ESA SP-250, pp. 409–412.
Donahue, T.M., Hoffman, J.H., Hodges, R.R., Jr., and Watson, A.J. (1982) “Venus was wet: A measurement of the ratio of deuterium to hydrogen,” Science 216, 630–633.
Donnison, J.R., and Sugden, R.A. (1984) “The distribution of asteroids diameters,” Mon. Not. Roy. Astron. Soc. 210, 673–682.
Drapatz, S., and Zinnecker, H. (1984) “The size and mass distribution of Galactic molecular clouds,” Mon. Not. Roy. Astron. Soc. 210, 11p–14p.
Duncan, M., Quinn, T., and Tremaine, S. (1987) “The formation and extent of the solar system comet cloud,” Astron. J. 94, 1330–1338.
Duncan, M., Quinn, T., and Tremaine, S. (1988) “The origin of short-period comets,” Astrophys. J. Letts. 328, L69–L73.
Duncan, M., Quinn, T., and Tremaine, S. (1989) “The long-term evolution of orbits in the Solar System: A mapping approach,” CITA preprint.
Everhart, E. (1967) “Intrinsic distributions of cometary perihelia and magnitudes,” Astron. J. 72, 1002–1011.
Everhart, E. (1968) “Change in total energy of comets passing through the Solar System,” Astron. J. 73, 1039–1052.
Everhart, E. (1972) “The origin of short-period comets,” Astrophys. Lett. 10, 131–135.
Everhart, E. (1976) “The evolution of comet orbits,” in B. Donn, M. Munna, W. Jackson, M. A’Hearn, and R. Harrington (eds.), The Study of Comets, IAU Coll. No. 25, NASA SP-393, pp. 445–464.
Everhart, E., and Marsden, B.G. (1983) “New original and future cometary orbits. III,” Astron, J. 93, 753–754.
Fernández, J.A. (1980a) “Evolution of comet orbits under the perturbing influence of the giant planets and nearby stars,” Icarus 42, 406–421.
Fernández, J.A. (1980b) “On the existence of a comet belt beyond Neptune,” Mon. Not. Roy. Astron. Soc. 192, 481–491.
Fernández, J.A. (1981a) “New and evolved comets in the solar system,” Astron. Astrophys. 96, 26–35.
Fernández, J.A. (1981b) “On the observed excess of retrograde orbits among long-period comets,” Mon. Not. Roy. Astron. Soc. 197, 265–273.
Fernández, J.A. (1982) “Dynamical aspects of the origin of comets,” Astron. J. 87, 1318–1332.
Fernández, J.A. (1985) “The formation and dynamical survival of the comet cloud,” A. Carusi and G.B. Valsecchi (eds.), Dynamics of Comets: Their Origin and Evolution, Reidel, Dordrecht, pp. 45–70.
Fernández, J.A. (1990) “Collisions of comets with meteoroids,” in C.-I. Lagerkvist, H. Rickman, B.A. Lindblad, and M. Lindgren (eds.), Asteroids, Comets, Meteors III, University of Uppsala, pp. 309–312.
Fernández, J.A., and Ip, W.-H. (1981) “Dynamical evolution of a cometary swarm in the outer planetary region,” Icarus 47, 470–479.
Fernández, J.A., and Ip, W.-H. (1983a) “On the time evolution of the cometary influx in the region of the terrestrial planets,” Icarus 54, 377–387.
Fernández, J.A., and Ip, W.-H. (1983b) “Dynamical origin of the short-period comets,” in C.-I. Lagerkvist and H. Rickman (eds.), Asteroids, Comets, Meteors, University of Uppsala, pp. 387–390.
Fernández, J.A., and Ip, W.-H. (1987) “Time-dependent injection of Oort cloud comets into Earth-crossing orbits,” Icarus 71, 46–56.
Fernández, J.A., and Jockers, K. (1983) “Nature and origin of comets,” Rep. Prog. Phys. 46, 665–772.
Fesenkov, V.G. (1922) “Sur les perturbations séculaires dans le mouvement des cometes non péiodiques par des étoiles voisines,” Publ. Russian Astrophys. Obervatory 1, 186–195.
Festou, M., Rickman, H., and Kamél, L. (1990) “The origin of nongravitational forces in comets,” in C.-I. Lagerkvist, H. Rickman, B.A. Lindblad, and M. Lindgren (eds.), Asteroids, Comets, Meteors III, University of Uppsala, pp. 313–316.
Foog, M.J. (1989) “The relevance of the background impact flux to cyclic impact/mass extinction hypotheses,” Icarus 79, 382–395.
Hamid, S.E., Marsken, B.G., and Whipple, F.L. (1968) “Influence of a comet belt beyond Neptune on the motions of periodic comets,” Astron. J. 73, 727–729.
Hasegawa, I. (1976) “Distribution of the aphelia of long-period comets,” Publ. Astron. Soc. Japan 28, 259–276.
Helin, E.F., and Shoemaker, E.M. (1979), “The Palomar planet-crossing asteroid survey 1973–1978,” Icarus 40, 321.
Heisler, J. and Tremaine, S. (1986) “The influence of the galactic tidal field on the Oort comet cloud,” Icarus 65, 13–26.
Heisler, J. and Tremaine, S. (1989) “How dating uncertainties affect the detection of periodicity in extinctions and craters,” Icarus 77, 213–219.
Hills, J.G. (1981) “Comet showers and the steady-state infall of comets from the Oort cloud,” Astron. J. 86, 1730–1740.
Holsapple, K.A., and Schmidt, R.M. (1982) “On the scaling of crater dimensions 2, Impact processes,” J.Geophys. Res. 87, 1849–1870.
Hughes, D.W. (1982) “Astroidal size distribution,” Mon. Not. Roy. Astron. Soc. 199, 1149–1157.
Hughes, D.W. (1987) “Cometary magnitude distribution and the fading of comets,” Nature 325, 231–232.
Hurnik, H. (1959) “The distribution of the directions of perihelia and the orbital poles of non-periodic comets,” Acta Astron. 9, 207–221.
Hut, P., Alvarez, W., Hansen, T., Kauffman, E.G., Keller, G., Shoemaker, E.M. and Weissman, P.R. (1987) “Comet showers as a cause of mass extinctions,” Nature 329, 118–126.
Hut, P., and Tremaine, S. (1985) “Have interstellar clouds disrupted the Oort comet cloud?,” Astron. J. 90, 1548–1557.
Ip, W.-H., and Fernández, J.A. (1988) “Exchange of condensed matter among the outer and terrestrial protoplanets and the effect on surface impact and atmospheric accretion,” Icarus 74, 47–61.
Ip, W.-H., and Fernández, J.A. (1990) “Steady-state injection of short-period comets from the trans-Neptunian cometary belt,” submitted to Icarus.
Ishida, K., Mikami, T., and Kosai, H. (1984) “Size distribution of asteroids,” Publ. Astron. Soc. Japan 36, 357–370.
Jackson, A.A., and Killen, R.M. (1988) “Infrared brightness of a comet belt beyond Neptune,” Earth, Moon, Planets 42, 41–47.
Joss, P.C. (1973) “On the origin of short-period comets,” Astron. Astrophys. 25, 271–273.
Kazimirchak-Polonskaya, E.I. (1976) “Review of investigations performed in the U.S.S.R. on close approaches of comets to Jupiter and the evolution of cometary orbits,” in B. Donn, M. Mumma, W. Jackson, M. A’Hearn, and R. Harrington (eds.), The Study of Comets, NASA SP-393, pp. 490–536.
Kowal, C.T. (1989) “A solar system survey,” Icarus 77, 118–123.
Kresák, L. (1975) “The bias of the distribution of cometary orbits by observational selection,” Bull. Astron. Inst. Czech. 26, 92–111.
Kresák, L. (1978) “The comet and asteroid population of the Earth’s environment,” Bull. Astron. Inst. Czech 29, 114–125.
Kresák, L., and Pittich, E.M. (1978) “The intrinsic number density of active long-period comets in the inner solar system,” Bull. Astron. Inst. Czech 29, 299–309.
Kuiper, G.P. (1951) “On the origin of the solar system,” in J.A. Hynek (ed.), Astrophysics, McGraw-Hill, New York, pp. 357–427.
Kumar, S., Hunten, D.M., and Pollack, J.B. (1983) “Nonthermal escape of hydrogen and deuterium from Venus and implication for loss of water,” Icarus 55, 369.
L”ust, R. (1984) “The distribution of the aphelion directions of long-period comets,” Astron. Astrophys. 141, 94–100.
Luu, J.X., and Jewitt, D. (1988) “A two-part search for slow-moving objects,” Astron. J. 95, 1256–1262.
Marsden, B.G. (1986) Catalogue of Cometary Orbits, (fifth edition), IAU Central Bureau for Astron. Telegrams, Cambridge, Mass.
Marsden, B.G. (1990) “The sungrazing comet group. II,” Astron. J. (in press).
Marsden, B.G., Sekanina, Z., and Everhart, E. (1978) “New osculating orbits for 110 comets and analysis of original orbits,” Astron. J. 83, 64–71.
Marsden, B.G., Sekanina, Z., and Yeomans, D.K. (1973) “Comets and nongravitational forces. V.,” Astron. J. 78, 211–225.
McKinnon, W.B., and Mueller, S. (1988) “Pluto’s structure and composition suggest origin in the solar, not a planetary, nebula,” Nature 335, 240–243.
Melosh, H.J. (1981) “Atmospheric breakup of terrestrial impactors,” in P.H. Schultz, and R.B. Merrill (eds.), Multipling Basins, Proc. Lundar Planet Sci. 12A, pp 29–35.
Mendis, D.A. (1973) “The comet-meteor stream complex,” Astrophys. Space Sci. 20, 165–176.
Morris, D.E., and Muller, R.A. (1986) “Tidal gravitational forces: The infall of ‘new’ comets and comet showers,” Icarus 65, 1–12.
Napier, W.M., and Clube, S.V.M. (1979) “A theory of terrestrial catastrophism,” Nature 282, 455–459.
Napier, W.M., and Staniucha, M. (1982) “Interstellar planetesimals — I, Dissipation of a primordial cloud of comets by tidal encounters with massive nebulae,” Mon. Not. Roy., astron. Soc. 198, 723–735.
Neukum, G. (1975) “Mars: A standard crater curve and possible new time scale,” Science 194, 1381–1387.
Oja, H. (1975) “Perihelion distribution of near-parabolic comets,” Astron. Astrophys. 43, 317–319.
Oort, J.H. (1950) “The structure of the cloud of comets surrounding the solar system and a hypothesis concerning its origin,” Bull. Astron. Inst. Neth. 11, 91–110.
Öpik, E.J. (1932) “Note on stellar perturbations on nearly parabolic orbits,” Proc. Am. Acad. Arts. Sci. 67, 1659–183.
Öpik, E.J. (1966) “Sun-grazing comets and tidal disruption,” Irish Astron. J. 7, 141–161.
Owen, T., Maillard, J.P., de Bergh, C., and Lutz, B.L. (1988) “Deuterium on Mars: The abundance of HDO and the value of D/H,” Science 240, 1767–1769.
Porter, J.G. (1963) “The statistics of comet orbits,” in B.M. Middlehurst and G.B. Kuiper (eds.), The Moon, Meteorites and Comets, The University of Chicago Press, pp. 550–572.
Pollack, J.B., and Yung, Y.L. (1980) “Origin and evolution of planetary atmospheres,” Ann. Rev. Earth Planet. Sci. 8, 425–487.
Rampino, M.R., and Stothers, R.B. (1984) “Terrestrial mass extinctions, cometary impacts and the sun’s motion perpendicular to the galactic plane,” Nature 308, 709–712.
Raup, D.M., and Sepkoski, J.J. (1984) “Periodicity of extinctions in the geologic past,” Proc. Natl. Acad. Sci. USA 81, 801–805.
Rickman, H. (1976) “Stellar perturbations of orbits of long-period comets and their significance for cometary capture,” Bull. Astr. Inst. Czech. 27, 92–105.
Rickman, H. (1986) “Masses and densities of comets Halley and Kopff,” in The Comet Nucleus Sample Return Mission Proc. Workshop, Canterbury, UK, ESA SP-249, pp. 195–205.
Safranov, V.S. (1972) “Ejection of bodies from the solar system in the course of the accumulation of the giant planets and the formation of the cometary cloud,” in G.A. Chebotarev, E.I. Kazimirchak-Polonskaya and B.G. Marsden (eds.), The Motion, Evolution of Orbits, and Origin of Comets, I.A.U. Symp. No. 45, Reidel, Dordrecht, Springer-Verlag, New York, pp. 329–334.
Sekanina, Z., and Yeomans, D.K. (1984) “Close encounters and collisions of comets with the Earth,” Astron. J. 89, 154–161.
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 Asteroids, T. Gehrels (ed.), Univ. of Arizona Press, Tucson, pp. 253.
Shoemaker, E.M., and Wolfe, R.F. (1982) “Cratering time scales for the Galilean satellites”, in Satellites of Jupiter, D. Morrison (ed.), Univ. of Arizona Press, Tucson, pp. 277–339.
Smoluchowski, R., and Torbett, M. (1984) “The boundary of the solar system,” Nature 311, 38–39.
Stagg, C.P., and Bailey, M.E. (1989) “Stochastic capture of short-period comets,” Mon. Not. Roy. Astron. Soc. 241, 507.
Stothers, R.B. (1984) “Mass extinctions and missing matter,” Nature 311, 17.
Stothers, R.B. (1988) “Structure of Oort’s comet cloud inferred from terrestrial impact craters,” The Observatory 108, 1–9.
Strom, R.G., and Neukum, G. (1988) “The cratering record on Mercury and the origin of impacting objects,” in Mercury, Eds. F. Vilas, C.R. Chapman and M.S. Matthews, Univ. of Arizona Press, Tucson, 336–373.
Talbot, R.J., and Newman, M.J. (1977) “Encounters between stars and dense interstellar clouds,” Astrophys. J. Suppl. Ser. 34, 295–308.
Torbett, M.V. (1986) “Injection of Oort cloud comets to the inner solar system by galactic tidal fields,” Mon. Not. Roy. Astron. Soc. 223, 885–895.
Tremaine, S. (1986) “Is there evidence for a solar companion star?,” in R. Smoluchowski, J.N. Bahcall, and M.S. Matthews (eds.), The Galaxy and the Solar System, Univ. of Arizona Press, Tucson, pp. 409–416.
Tyror, J.G. (1957) “The distribution of the directions of perihelia of long-period comets,” Mon. Not. Roy. Astron. Soc. 117, 369–379.
Van Woerkom, A.J.J. (1948) “On the origin of comets,” Bull. Astr. Inst. Neth. 10, 445–472.
Wetherill, G.W. (1975) “Late heavy bombardment of the moon and terrestrial swarm subsequent to the formation of the Earth and the Moon,” In Proc. 8th Lunar Sci. Conf., pp. 1–16.
Wetherill, G.W., and Shoemaker, E.M. (1982) “Collision of astronomically observable bodies with the Earth,” in Geological Implications of Impacts of Large Asteroids and Comets on the Earth, Geological Soc. Amer. Sp. Pap., 190, 1.
Weissman, P.R. (1980a) “Stellar perturbations of the cometary cloud,” Nature 288, 242–243.
Weissman, P.R. (1980b) “Physical loss of long-period comets,” Astron. Astrophys. 85, 1919–196.
Weissman, P.R. (1983) “The mass of the Oort cloud,” Astron. Astrophys. 118, 90–94.
Weissman, P.R. (1985a) “Dynamical evolution of the Oort cloud,” in A. Carusi and G.B. Valsecchi (eds.), Dynamics of Comets: Their Origin and Evolution, Reidel, Dordrecht, pp. 87–96.
Weissman, P.R. (1985b) “Cometary dynamics,” Sp. Sci. Rev. 41, 299–349.
Weissman, P.R. (1985c) “Terrestrial impactors at geological boundary events: Comets or asteroids,” Nature 314, 517–518.
Weissman, P.R. (1990) “The Oort cloud,” Nature (in press).
Whipple, F.L. (1950) “A comet model. I. The acceleration of comet Encke,” Astrophys. J. 111, 375–394.
Whipple, F.L. (1964) “Evidence for a comet belt bezond Neptune,” Proc. Natl. Acad. Sci. 51, 711.
Whitmire, D.P., and Jackson, A.A. (1984) “Are periodic mass extinctions driven by a distant solar companion?,” Nature 308, 713–715.
Yeomans, D.K., and Chodas, P.W. (1989) “An asymmetric outgassing model for cometary nongravitationa! accelerations,” Astron. J. 98, 1083–1093.
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Fernández, J.A., Ip, WH. (1991). Statistical and Evolutionary Aspects of Cometary Orbits. 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_21
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