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

Abstract

The bulk densities of 82 samples of 72 ordinary chondrites (OCs) were measured to an accuracy of ∼1% using a modified Archimedian method. We found the average bulk density to be 3.44 ± 0.19 g/cm3 for the H group, 3.40 ± 0.15 g/cm3 for the L group, and 3.29 ± 0.17 g/cm3 for the LL group (± represent 1σ). Bulk density measurements of 11 pieces of one fall, Pultusk (H group), were also found to vary considerably (3.31 to 3.63 g/cm3). To investigate controls on bulk density within the OCs, we compared density with bulk chemical composition (the ratio of Fe metal to total 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 whereas bulk density varies from about 3.0 to 3.8 g/cm3. Slight but systematic differences in average density between the H, L, and LL groups presumably relate to differences in metallic Fe abundance. However, considerable overlap between OC groups and the wide range of bulk densities within each group suggest differences in porosity dominantly control variations of density within the OC subgroups.