Densities and porosities of ordinary chondrite meteorites: Study of Mercurian topography using digital elevation models.

摘要

Densities and porosities of meteorites are physical properties that can be used to infer characteristics of asteroid interiors. I report density and porosity measurements of ordinary chondrite meteorites. Bulk volume was measured using a modified Archimedian method, while grain volume was measured using helium gas pycnometry; I provide a quantification of error for the methods used in this study. Based on the porosity measurements, no significant correlation exists between porosity and petrologic grade, chemical group, sample mass, bulk and grain density, or shock level.; I compared the bulk density of the asteroid 433 Eros (2.67 +/- 0.03 g/cm3) with that of ordinary chondrites (3.40 g/cm3 ), to estimate that the total porosity of the asteroid is 21--33%. Structural porosity, best estimated to be ∼20%, is constrained to be between 6% and 33%. Based on this porosity estimate and additional evidence (such as structural features seen on the surface of Eros), I conclude that Eros is a heavily fractured body, but there is no evidence that Eros was ever catastrophically disrupted and reaccumulated into a rubble pile structure.; Digital elevation models (DEMs) derived from Mariner 10 stereo images of the planet Mercury were examined, but revealed a characteristic smoothing effect on topography. The lack of documentation of the methods used to create the DEMs as well as no error analysis prompted the development of a new stereo matching program. The new stereo matching software uses an adaptive least squares algorithm and a sheet-growth algorithm. This software will be used to systematically reprocess the Mariner 10 stereo data in order to create a robust topographic product.