Giacomo Criniti is an extremely worthy recipient of the John C. Jamieson Student Paper Award for his exceptional contribution to the field of mineral physics made by determining the elastic properties of bridgmanite, Earth’s most abundant mineral, at pressures compatible with the deep lower mantle, as published in the Journal of Geophysical Research: Solid Earth (Criniti et al., 2021, https://doi.org/10.1029/2020JB020967). The Brillouin scattering measurements of MgSiO3 bridgmanite presented in this paper include the first single-crystal measurements of the longitudinal wave velocity, vP, of bridgmanite at pressures of Earth’s deep lower mantle. Previous Brillouin scattering studies on both single-crystal and polycrystalline bridgmanite samples either have been carried out only up to approximately 45 gigapascals, or have been only able to constrain the aggregate shear wave velocities at deep mantle conditions. The main problem that is elegantly addressed in this paper is that when high-pressure acoustic phonon measurements are made on bridgmanite in the diamond anvil cell using Brillouin scattering, the bridgmanite vP signal, which is increasing in frequency with increasing pressure, merges and is obscured by the much larger S wave peak of the diamond anvils, at pressures higher than 30–45 gigapascals. This prevents the velocity from being determined at higher pressures. Thanks to his exceptional experimental skills and his deep understanding of crystallography and mineral elasticity, Giacomo was able to align both the diamond anvils and bridgmanite crystals to allow the vP signal to be measured on the high-frequency side of the diamond vS signal, at pressures above 50 gigapascals. By making simultaneous single-crystal measurements of density and acoustic wave velocities, Giacomo obtained a self-consistent data set, which places strong constraints on the elastic behavior of bridgmanite up to pressures of 80 gigapascals. Using the newly determined bridgmanite elastic properties to compute wave velocities for a pyrolite bulk composition at lower mantle conditions, he found good agreement with seismic reference models, suggesting that there is no basis in seismology for considering that the average Earth’s lower mantle has a different composition than the upper mantle. This is contrary to what was suggested by studies on polycrystalline bridgmanite in which no measurements of vP were possible. These measurements were only possible through Giacomo’s extraordinary experimental abilities and dogged perseverance. —Tiziana Boffa Ballaran and Daniel J. Frost, Bayerisches Geoinstitut, University of Bayreuth, Bayreuth, Germany

Being an extremely enthusiastic person when it comes to discovering new things, my choice of joining the Bayerisches Geoinstitut of the University of Bayreuth was likely the best one I’ve made in my career so far. The institute is an experimentalist’s wonderland when it comes to high-pressure research, and therefore it seems only natural to me that I fell in love with experimental mineral physics when I first got to work with Tiziana Boffa Ballaran. Tiziana is both a brilliant crystallographer and a caring supervisor, but the project she assigned me for my master’s thesis was certainly not an easy one. The idea was to compress single crystals of MgSiO3 bridgmanite in diamond anvil cells to high enough pressure to observe a crossover between the sample vP and diamond vS by Brillouin scattering. This represents both a crystallographic problem and an experimental challenge. A lot of trial and error was involved in finding a protocol to define the most suitable orientation and size of bridgmanite crystals, focused ion beam milling strategy, and sample loading in the diamond anvil cell. Fortunately, our technician Raphael Njul was always ready to help by preparing perfect single-crystal platelets in a very short time. Even thus, assembling a single cell took on average of 1 week, and the process would have driven me crazy were it not for Alexander Kurnosov. No matter the hour or the day, Alex was always available to share his extensive knowledge about diamond anvil cells and Brillouin scattering and help with troubleshooting in the data collection and analysis. Last but not least, it was thanks to Daniel Frost and his teachings about the ways of thermodynamics that I was able to put such valuable data into the right context. In the end, the project proved to be way harder and more time consuming than I expected, and by the time it was finished I was already at the end of the first year of my Ph.D. Writing a paper is a team effort, and if it were not for all the people I mentioned, it would have been impossible for me to finish. This is why I am extremely grateful to everyone who supported me throughout this project and to the Mineral and Rock Physics section of AGU for recognizing our efforts by awarding me the 2022 John C. Jamieson Student Paper Award. —Giacomo Criniti, Bayerisches Geoinstitut, University of Bayreuth, Bayreuth, Germany