The density, porosity and pore morphology of fall and find ordinary chondrites

S.J. Li, S.J. Wang, B.K. Miao, Y. Li, X.Y. Li, X.J. Zeng, Z.P. Xia


JGR Planets, First published: 28 October 2019

“Density, porosity, and pore morphology constitute the basic physical properties of meteorites. These properties of 214 fragments from 163 different ordinary chondrites (OCs), including falls, non‐Antarctic finds, and Antarctic finds, were measured, calculated, and investigated. Of all the measured OCs data, densities and porosities of 37 OC falls (14 H, 17 L, and 6 LL), 31 non‐Antarctic finds (9 H and 22 L), and 95 Antarctic finds (24 H and 73 L) are reported for the first time. The individual masses of all the meteorite fragments measured in this study ranged between 0.8953 g and 7.7133 g, and these masses were too low to be measured by the Archimedean glass bead method. Our study indicated that the grain density and porosity of find OCs are significantly reduced by terrestrial weathering. As a result, such OCs are not suitable for studying the physical properties of meteorites. Shock degree ≤S2 slightly increases the measurable porosities of the meteorites by generating a certain amount of very fine cracks in the silicates to link some isolated pores with the measurable pores. Shock degree over S2 significantly reduces the porosities of meteorites by compacting or even melting the material. Weathering reduced the porosities via space filling of weathering products. Shock load over S2 reduced the porosities of the meteorites by minerals compressing or melting. Moreover, the shock load over S2 also converted intergrain irregular pores into intragrain cracks. Thermal metamorphism mainly changed the pore morphology (size) by pore merging during mineral recrystallization. The pore morphology also plays a significant role in controlling the friability of OCs.”

“Key Points

  • The high precision densities and porosities of 214 fragments from 163 different ordinary chondrites (OCs) including falls, non‐Antarctic finds, and Antarctic finds were measured and calculated. The pore morphology of some selected OCs were investigated
  • Non‐Antarctic find OCs usually suffered more serious terrestrial weathering than Antarctic OCs. Both kinds of OCs are not suitable for porosity investigation
  • Weak shock (<S2) may increase the porosity of a meteorite by generating tiny cracks to link some isolated pores. Shock degree ≥S3 will compact the material and significantly reduce the porosities of OCs
  • Thermal metamorphism can merge small pores into larger ones
  • The high precision grain density and porosity data of OCs can be used to infer in inner structure of an OC analogous asteroid”