Origin of multikilometer earth- and mars-crossing asteroids: A quantitative simulation

Science

Volumn 281, Issue 5385, 1998, Pages 2022-2024

  Migliorini, Fabio ^a,b   Michel, Patrick ^b,c   Morbidelli, Alessandro ^c   Nesvorný, David ^c   Zappalà, Vincenzo ^b  

^a ARMAGH OBSERVATORY   (United Kingdom)

^b OSSERVATORIO ASTRONOMICO DI TORINO   (Italy)

^c UNIVERSITÉ CÔTE D'AZUR   (France)

Author keywords

[No Author keywords available]

Indexed keywords

ARTICLE; ASTRONOMY; GRAVITY; METEOROLOGICAL PHENOMENA; MOTION; PRIORITY JOURNAL;

EID: 0032566588     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.281.5385.2022     Document Type: Article

References (21)

1. See, for instance, R. Greenberg and M. Nolan, in Asteroids II. R. Binzel, T. Gerhels, M. S. Matthews, Eds. (Univ. of Arizona Press, Tucson, AZ, 1989), pp. 778-804.
2. 6 secular resonance, which occurs when the mean precession rate of the asteroid's perihelion equals that of Saturn. These are by far the most efficient resonances for the transport of bodies to large eccentricities.
3. For a list of ECAs and MCAs with perihelion distance < 1.3 AU (classically defined as Amors asteroids), see http://cfa-www.harvard.edu/iau/lists/ Unusual.html.
4. B. J. Gladman et al., Science 277, 197 (1997).
5. Here ECAs are defined as the asteroids with perihelion and aphelion distance smaller and larger, respectively, than 1 AU, whereas MCAs are defined as those that are not currently Earth crossers and intersect the orbit of Mars within one precession cycle of their orbit. To identify all MCAs, we have integrated for 300,000 years the evolution of all the asteroids in the 1997 update of the catalog [E. Bowell, K. Muinonen, L. H. Wasserman, in Asteroids, Comets, Meteors, A. Milani, M. DiMartino, A. Cellino, Eds. (Kluwer, Dordrecht, Netherlands, 1994), pp. 477-481] with perihelion distance smaller than 1.78 AU. An asteroid has been categorized as MCA if it passes through the torus defined by heliocentric distance r between 1.341 and 1.706 AU and vertical coordinate |z| < r sin(6.4°). These bounds account for a martian maximal eccentricity and inclination of 0.12 and 6.4°, respectively. Asteroid diameters have been estimated assuming the albedos reported in Table 1, if IRAS measurements are not available.
6. M. Menichella, P. Paolocchi, P. Farinella, Earth Moon Planets 72, 133 (1996); for a discussion, see also conclusions of (4).
7. Numerical integration was done with the swift-_rmvs3 numerical integrator [H. Levison and M. Duncan, Icarus 108, 18 (1994)].
8. Proper elements were computed by averaging the orbital elements over a 10-My running window. The initial proper elements are therefore related to the first 10 My of evolution.
9. A detailed analysis of the chaotic structure of the asteroid belt and its relationship with Fig. 2 is reported in A. Morbidelli and D. Nesvorný, Icarus, in press. For three-body resonances see D. Nesvorný and A. Morbidelli, Astron. J., in press.
10. A detailed analysis of the chaotic structure of the asteroid belt and its relationship with Fig. 2 is reported in A. Morbidelli and D. Nesvorný, Icarus, in press. For three-body resonances see D. Nesvorný and A. Morbidelli, Astron. J., in press.
11. 6 resonance or the closely located 4/1 resonance with Jupiter, and 20% by other resonances.
12. This is done by multiplying the number of MCAs larger than 5 km by the fraction of integrated MCAs that are found on ECA orbits as a function of time. We restrict our considerations to asteroids larger than 5 km for which observational biases can be neglected in the first approximation.
13. Secular resonances with the inner planets are important in this phase; see P. Michel and Ch. Froeschlé, Icarus 128, 230 (1997) and P. Michel, ibid., 129, 348 (1997).
14. Secular resonances with the inner planets are important in this phase; see P. Michel and Ch. Froeschlé, Icarus 128, 230 (1997) and P. Michel, ibid., 129, 348 (1997).
15. 16 resonance occurs when the mean precession rate of the asteroid's node equals that of Jupiter.
16. In principle, our argument might be circular: If comets' contribution were nonnegligible, we could have underestimated the number of ECAs larger than 5 km by assuming a typical asteroidal albedo. Note, however, that most of the albedos measured for the Near Earth asteroids are in the range considered by us [D. F. Lupishko and M. Di Martino, Planet. Space Sci. 46, 47 (1998)].
17. A. Milani and Z. Knezevic, Icarus 107, 219 (1994).
18. About 10,000, according to R. Jedicke and T. S. Metcalfe [Icarus 131, 245 (1998)]; extrapolating the size distribution of the asteroid families, this number is increased by 50% [V. Zappala and A. Cellino, in Completing the Inventory of the Solar System, ASP Conf. Series 107, 29 (1996)].
19. The Tisserand invariant is related to the relative velocity at encounter between the body and the planet. If the planet is on a circular orbit, the encounter velocity vector is rotated during the encounter, but its norm is preserved [G. Valsecchi and A. Manara, Astron. Astrophys. 323, 986 (1997)].
20. 0.16 for 2.1 ≤ a < 2.36; 0.13 for 2.36 ≤ a < 2.48; 0.14 for 2.48 ≤ a < 2.61; 0.11 for 2.61 ≤ a < 2.75; 0.12 for 2.75 ≤ a < 2.80; 0.10 for 2.80 ≤ a < 3.00.
21. We thank the European Space Agency and the Conseil Général des Alpes Maritimes for postdoctoral grants provided to P. Michel and D. Nesvorný, respectively.