SIBLING SANDBLASTING AND THE SMOOTHNESS OF GASPRA AND IDA

Both Asteroid 951 Gaspra and 243 Ida look like smooth, rounded pebbles and neither have the expected angular, jagged-faceted appearance of a rock fragment produced by a hypervelocity impact. We suggest that the y were both rough and sharp-edged at ''birth'' and that the rounding o ff that we now see is the result of a multitude of low-velocity collis ions (at around 0.065 to 0.1 km s(-1)) with the much smaller sibling a steroidal fragments that were born at the same time by the collisions that produced the respective asteroidal families. (C) 1998 Elsevier Sc ience Ltd. All rights reserved.