The endurance lifetime of ice fragments in cometary streams

The endurance lifetime against sublimation of meter- to decameter-sized ice fragments are calculated for typical cometary orbits. It is found that suc h bodies can survive for multiple perihelion passages. For fragments travel ing along orbits similar to those of typical meteor shower producing comets , the sublimation mass loss rate drives radial variations equivalent to 1-0 .5 m per orbit. We review the available data with respect to the possible p resence of large objects within the Perseid, Lyrid, Leonid and alpha -Capri cornid streams. Invoking cometary aging and surface fragmentation events as the mechanism for placing large meteoroids within cometary streams, we fin d no compelling reasons to doubt that large meteoroids are intermittently p resent in most, if not all cometary-derived meteoroid assemblages. (C) 2001 Elsevier Science Ltd. All rights reserved.