Sound velocity of mantle minerals and aggregates

Ultrasonic interferometry and Brillouin spectroscopy have been largely used to measure sound velocity of minerals. However, application of Brillouin spectroscopy is not suited to opaque, Fe-rich minerals (as the case for Mars) and applications of ultrasonic interferometry in multi-anvil press are still prohibitive over planetary P-T conditions.

An innovative and complementary approach is offered by the combination of picosecond acoustics and restively heated and laser heated diamond anvil cell. Picosecond acoustics is a pump-probe technique that belongs to the family of modern ultrafast optical methods and allows longitudinal velocity measurements on metals, minerals and aggregates over a P-T range covering not only the conditions of the interiors of relatively small telluric planes such as Mercury and Mars, but as well as those of larger bodies such as Venus and the Earth.

The obtained results will be essential to the interpretation of seismic data (Apollo records for the Moon and forthcoming InSight mission to Mars) and to produce accurate mineralogical models of planetary mantles. Specific to Mars, combining these new laboratory measurements with data from InSight, we will be able to discriminate between proposed compositional models.

Photo of picosecond acoustic setup, wave propagation in solid media.