Gas pycnometer for determining the density and porosity of returned asteroid Bennu samples

Density and porosity measurements are critical to analyzing asteroid samples, typically found on Earth. The OSIRIS-REx project presents a unique opportunity to analyze carbon-rich samples from an actual asteroid, Bennu. Accurate porosity measurements can indicate trapped moisture during the formation of an astronomical body.

The team applied gas pycnometry theory to design a system that mitigated risk of sample contamination and damage, met material and spatial requirements, and accommodated various sample sizes.

The students used error analysis and modeling to determine optimal volume and number of reference chambers. Without lubricants, non-approved materials or shearing contact points, they designed a novel chamber with a gas-tight seal. They used a pressure transducer and LabVIEW VI for measurements. The team combined pressure measurements, the ideal gas law, and 3D sample measurements to determine porosity. Automation allowed for rapid repetition, minimal change in the sample environment, and precise measurements.