Cometary nuclei and tidal disruption: The geologic record of crater chains on Callisto and Ganymede
Icarus, 121 (2):
249--274 (1996)Abstract
Prominent crater chains on Ganymede and Callisto are most likely the
impact scars of comets tidally disrupted by Jupiter and are not secondary
crater chains, We have examined the morphology of these chains in
detail in order to place constraints on the properties of the comets
that formed them and the disruption process. In these chains, intercrater
spacing varies by no more than a factor of 2 and the craters within
a given chain show almost no deviation from linearity (although the
chains themselves are on gently curved small circles). All of these
crater chains occur on or very near the Jupiter-facing hemisphere,
For a given chain, the estimated masses of the fragments that formed
each crater vary by no more than an order of magnitude. The mean
fragment masses for all the chains vary by over four orders of magnitude
(W. B, McKinnon and P. M. Schenk 1995, Geophys. Res. Left. 13, 1829-1832),
however. The mass of the parent comet for each crater chain is not
correlated with the number of fragments produced during disruption
but is correlated with the mean mass of the fragments produced in
a given disruption event. Also, the larger fragments are located
near the center of each chain. All of these characteristics are consistent
with those predicted by disruption simulations based on the rubble
pile cometary nucleus model (in which nuclei are composed on numerous
small fragments weakly bound by self-gravity), and with those observed
in Comet D/Shoemaker-Levy 9. Similar crater chains have not been
found on the other icy satellites, but the impact record of disrupted
comets on Callisto and Ganymede indicates that disruption events
occur within the Jupiter system roughly once every 200 to 400 years,
(C) 1996 Academic Press,Inc.