Earth-approaching asteroid streams

Abstract

The osculating orbital elements of 139 Earth-approaching asteroids ( (through 1990KA) are compared with the D discriminants to identify the asteroids traveling in the most similar orbits. No Apollo associations are noted, but three Amor groups are identified whose members, if they were meteors, would be classified as comprising a shower or stream. Two of the streams have five members each, and are shown to be inconsistent with random groupings. One involves two V type asteroids, and the other five-member group has a secondary minimum in mutual orbital separation in the main belt, perhaps pointing to the location of a collision. The three meteorites with known orbits are also examined. Innisfree is most closely related to 1989DA, Pribram is questionably associated with 4486 (1987SB), and Lost City may be an outlier of a four-member asteroid association. Independent corroboration of these asteroid streams is provided by Halliday et al. (1990, Meteoritics 25, 93–99), who find four streams among 89 meteorite-producing fireballs, three of which are evidentally the meteor components of the asteroid streams. It is remarkable that in the face of disturbing perturbations asteroid streams could survive for any length of time, but if they are true nonrandom associations then the opportunity exists for studying an “exploded” asteroid in the near-Earth environment and through examination of pieces dropped by stream fireballs. The prediction is made that near-Earth asteroid search projects should find more members if they search the mean orbit of the streams.