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 such bodies can survive for multiple perihelion passages. For fragments traveling 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 presence of large objects within the Perseid, Lyrid, Leonid and alpha -Capricornid streams. Invoking cometary aging and surface fragmentation events as the mechanism for placing large meteoroids within cometary streams, we find no compelling reasons to doubt that large meteoroids are intermittently present in most, if not all cometary-derived meteoroid assemblages. (C) 2001 Elsevier Science Ltd. All rights reserved.