Decoherence time scales for "meteoroid streams"

Abstract

We explore the orbital dynamics of Earth-crossing objects with the intent to understand the time scales under which an "orbital stream" of material could produce time-correlated meteorite falls. These meteoroid streams have been suggested to be associated with three well-known meteoritedropping fireballs (Innisfree, Peekskill, and Příbram). We have performed two different analyses of the statistical significance of the "orbital similarity," in particular calculating how often orbits of the same level of similarity would come from a random sample. Secondly, we have performed extremely detailed numerical integrations related to these three cases, and we find that if they were streams of objects in similar orbits, then they would become "decoherent" (in the sense that the day-of-fall of meteorites of these streams become almost random) on time scales of 10^4-10^5 yr. Thus, an extremely recent breakup would be required, much more recent that the cosmic ray exposure ages of the recovered falls in each case. We conclude that orbital destruction is too efficient to allow the existence of long-lived meteoroid streams and that the statistical evidence for such streams is insufficient; random fall patterns show comparable levels of clustering.