How elastic are meteorites? Laser ultrasound has the answer

Researchers at the University of Nottingham, UK, have measured the stiffness of space rock for the first time.

The team used spatially resolved acoustic spectroscopy (SRAS++) to measure the properties of the Gibeon meteorite.  

The SRAS++ machine uses lasers to make and detect acoustic waves that travel on the surface of the material, removing any need to touch the sample.

Many meteorites are made of crystalline materials, formed under exotic conditions that cannot be replicated on Earth.

The stiffness of the crystals that make up these materials has historically been difficult to measure, and the usual route is to grow a special single crystal, which in this case is not possible.

Uusing a new technique developed and patented at the University of Nottingham, this property has been measured for the first time.

Meteorites provide access to information on the formation and evolution of planetary bodies that are otherwise difficult to study.

The nature of these samples and their relative scarcity means that non-destructive analysis techniques are needed to study their properties.
Understanding their properties develops the understanding of the formation of the solar system and the planets.

Lead author of the study, Wenqi Li, from the university’s Optics and Photonics research group, explains, ‘These materials have evolved in unique conditions over millions of years to form these amazing structures and patterns. These conditions cannot be reproduced on Earth and meteorites have amazing large-scale microstructure and phase mixtures which gives mechanical and elastic properties that are quite different to the man-made iron-nickel alloys we can produce on Earth.’

Studying these samples can also help develop an understanding of alloys used for aerospace and industrial applications, suitable for constructing extraterrestrial structures, making meteors a suitable source of material for future manufacturing in space.

Associate Professor Richard Smith notes, ‘There are no published values to directly compare the results of this study, as non-destructive measurements of the single crystal elasticity on granular material has not previously been possible.

'So, we compared our results with theoretical values for man-made iron-nickel alloys. We also calculated the bulk properties from our single-crystal elasticity measurements and compared them to published measurements on the Gibeon meteorite and they also agree well.’

Future work will image the changes in the local elastic properties from the centre to the periphery of the meteorites to understand the formation of these materials.

The work is published, Measuring the elastic properties of the Gibeon meteorite using laser ultrasound - ScienceDirect