Recent reports suggest that crater chains exist on Earth, possibly formed by
weak asteroids or comets tidally stretched apart by the Moon (analogous to
comet Shoemaker-Levy 9 at Jupiter) with the resulting fragment trains
proceeding directly to strike the Earth. By modeling tidal disruption by the
Earth and Moon of particulate bodies held together by self-gravity, we find
that the formation rate of crater chains on the Moon is ~10 times the
corresponding terrestrial rate. The number of known lunar crater chains
(~1) and the relative youth of the Earth's surface together suggest that
terrestrial crater chains, if they exist, form by another process.