Long-term dynamics of bright bolides

We have integrated backward and forward in time the orbits of 20 very brigh t bolides (with visual magnitude brighter than -10) over a time span of 5 M yr or more. The sample was mainly selected among events observed during the period between 1993 and 1996, but we have included also three older, parti cularly interesting events (Abee, 1952; Glanerbrug, 1990; and EN220991, 199 1). For a large part of the sample, the orbit is known with sufficient accu racy from the reduction and analysis of photographic data. However, there a re also some cases in which lower-accuracy orbital data were derived from o ther techniques, such as visual, seismic, and radar observation. For these events we have used two or three alternative initial orbits, consistent wit h the existing uncertainty. The results of our integrations show a great di versity of orbital evolution patterns, consistent with the behaviour of lar ger near-Earth objects. The most frequent fate (42% of the cases) is solar collision, followed by hyperbolic ejection (17%), and the average dynamical lifetime is of the order of 10 Myr. Three bolides either have initially or achieve later Aten-type or Q < 1 AU orbits, similar to the fraction of suc h objects in the near-Earth asteroid population. Only 2 bolides have a clea r comet-like dynamical behaviour dominated by Jovian encounters, although a blation properties indicate that the fraction of very weak bolides is proba bly higher.