The Non-Destructive Measurement of Meteorite Density and Porosity

English Abstract:

There are 44 compositional types, subtypes, and metamorphic grades of meteorites which represent an invaluable resource of “free” geological material from asteroids. The measurement meteorite density and porosity, provides fundamental data on asteroid physical properties and insight into their structure and evolution. Until the late 1990’s measurements of meteorite density and porosity used the standard geological techniques. For bulk volume and bulk density, the sample was weighed first in air and then suspended in water. This method gives a good estimate of the bulk density, but does not take into account any penetration of the water into the pore space. Another approach for bulk density was to cut the meteorite into a standard cube. To determine porosity some workers used penetrating fluids like carbon tetrachloride to access internal void spaces. The major drawback of these methods is the contamination the meteorite, which increases its weathering and potentially damages its use for future studies.

Consolmagno and Britt (1998) developed a method for the measurement of meteorite bulk densities using glass beads instead of water. The glass bead method, combined with helium gas pycnometry minimizes sample contact and thus contamination. Since then, the combination of glass beads for bulk density and helium gas pycnometry for porosity has become the standard for meteorite physical property measurements. The new developing standard is the use of 3-D laser scanning for bulk volume allowing for very minimal contact with the meteorite during the measurements.