Mathilde: Size, shape, and geology

The Near Earth Asteroid Rendezvous (NEAR) spacecraft images of C-type aster oid Mathilde show it to have a mean radius of 26.5 +/- 1.3 km, The asteroid is geologically distinguished by its low mean density (1.3 +/- 0.2 g cm(-3 )) and by at least four craters with diameters equal to or greater than Mat hilde's mean radius, The large craters and their unremarkable appearance su ggest formation without significant damage to the asteroid outside the fina l crater volume and indicates the ability of at least this type of asteroid to survive very large impacts without disruption. There are suggestions of structures such as faults or layers. Preservation of such structures would imply that objects that are poor transmitters of impact seismic energy can still maintain some mechanical fabric, and their surface exposure may impl y inefficient retention of ejecta from large craters. (C) 1999 Academic Pre ss.