Bulk density of ordinary chondrite meteorites and implications for asteroidal internal structure

The bulk densities of 82 samples of 72 ordinary chondrites (OCs) were measu red to an accuracy of similar to1% using a modified Archimedian method. We found the average bulk density to be 3.44 +/- 0.19 g/cm(3) for the H group, 3.40 +/- 0.15 g/cm(3) for the L group, and 3.29 +/- 0.17 g/cm(3) for the L L group (+/- represent 1 sigma). Bulk density measurements of 11 pieces of one fall, Pultusk (H group), were also found to vary considerably (3.31 to 3.63 g/cm(3)). To investigate controls on bulk density within the OCs, we c ompared density with bulk chemical composition (the ratio of Fe metal to to tal Fe; the ratio of total Fe to SiO2; the ratio of FeO to total Fe and MgO ). Within each OC group, bulk chemical composition is nearly invariant wher eas bulk density varies from about 3.0 to 3.8 g/cm(3). Slight but systemati c differences in average density between the H, L, and LL groups presumably relate to differences in metallic Fe abundance. However, considerable over lap between OC groups and the wide range of bulk densities within each grou p suggest differences in porosity dominantly control variations of density within the OC subgroups.