The Near-Earth Asteroid Rendezvous (NEAR) spacecraft determined that the bulk
density of C-class asteroid Mathilde was 1.3 g cm 
(Veverka et al. 1998;
Yeomans et al. 1998). The surface of Mathilde, however, has the same
spectroscopic signature as carbonaceous chondrite meteorites, whose typical
density is somewhere near 2 g cm (Wasson 1985). The only plausible way
to explain Mathilde's low density is to assume its interior contains large
void spaces or that it consists of small fragments with substantial
interparticle porosity. Either way, Mathilde can be considered a rubble pile
rather than a monolithic fragment.