We report the discovery of grooves in Galileo high-resolution images o
f Gaspra. These features, previously seen only on Mars' satellite Phob
os, are most likely related to severe impacts. Grooves on Gaspra occur
as linear and pitted depressions, typically 100-200 m wide, 0.8 to 2.
5 km long, and 10-20 m deep. Most occur in two major groups, one of wh
ich trends approximately parallel to the asteroid's long axis, but is
offset by some 15-degrees; the other is approximately perpendicular to
this trend. The first of these directions falls along a family of pla
nes which parallel three extensive flat facets identified by Thomas et
al., Icarus 107. The occurrence of grooves on Gaspra is consistent wi
th other indications (irregular shape, cratering record) that this ast
eroid has evolved through a violent collisional history. The bodywide
congruence of major groove directions and other structural elements su
ggests that present-day Gaspra is a globally coherent body. (C) 1994 A
cademic Press, Inc.