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Gas gun shock experiments on cyclotrimethylenetrinitramine (RDX)-based explosive compositions that employ embedded gauge particle velocity tracers have noted a significant amount of electrical noise when compared to other explosive formulations. This paper reexamines previously published embedded gauge data on Cyclotols (60–80 wt. % RDX) to quantify the electromagnetic behavior of these materials. The primary observation is a fourfold increase in the electrical noise when Cyclotols are shocked above 4.22 ± 0.08 GPa. Electromagnetic gauge noise is also observed within particle velocity traces in reactive growth and off-Hugoniot shocks, although at higher pressures than the direct shock case, suggesting a temperature- or kinetically dependent transition. In all cases, the electrical noise disappears upon detonation. By comparing with the static high-pressure phase diagram of RDX, we interpret this change in electromagnetic behavior to be a change in the RDX crystal structure to a piezoelectric phase, although it is uncertain whether the γ or ε phase is responsible for the observed behavior. [ABSTRACT FROM AUTHOR]

Shock compression experiments on natural compositions are imperative to accurately model planetary accretion and the interior dynamics of planets. Combining shock compression experiments from the Sandia Z Machine and the OMEGA EP laser facility with density functional theory‐based molecular dynamics calculations, we report the first pressure‐density‐temperature (P‐ρ‐T) relationship of natural iron (Fe)‐bearing olivine ((Mg0.91Fe0.09)2SiO4) on the principal Hugoniot between 166 and 1,465 GPa. Additionally, we report the first reflectivities of natural olivine liquid in this pressure range. Compared to the magnesium‐endmember forsterite (Mg2SiO4), the presence of Fe in typical mantle abundance (∼9 wt% FeO) alters the US‐uP relation of olivine. On the other hand, the shock temperature and reflectivity of olivine are indistinguishable from forsterite where experimental conditions overlap. Both forsterite and olivine increase in reflectivity (and hence optical conductivity) with increasing temperature, with a maximum reflectivity of ∼31% at shock velocities greater than 22 km/s (∼800 GPa). Plain Language Summary: Olivine is the most abundant mineral in Earth's upper mantle and in the mantles of other rocky bodies in the Solar System. While previous studies of this material have focused on iron‐free compositions, natural olivine contains varying amounts of iron. The data presented here describe how olivine responds to shock waves, which are important for understanding the outcomes of collisions onto growing planets. With these data, we can more robustly model the pressure and temperature conditions reached in impact situations, as well as the relative amounts of melting and vaporization that will occur from an impact. These parameters are key to understanding the chemistry that can occur as planets grow. We have also found that olivine liquid becomes highly reflective at high temperatures, which suggests that it is electrically conductive. This observation is important for understanding the generation of magnetic fields in very hot or molten planets. Key Points: Combined dynamic compression data with computations to define the pressure‐density‐temperature relation on the Hugoniot of olivineThe principal Hugoniot of olivine diverges from Fe‐free forsterite over the experimental conditionsOlivine liquid is optically conductive at high temperatures and high pressures [ABSTRACT FROM AUTHOR]