| In-situ high-pressure and high-temperature experiments are invaluable to understanding the interiors of planets primarily giving us insight into the relationship of pressure and temperature on the chemical and physical characteristics of planetary materials as well as testing current theories of planetary accretion, differentiation and evolution throughout a planet's lifetime.;X-ray diffraction was used to measure the volume response to pressure and temperature of a natural peridotite at lower-mantle pressures. A lower mantle composed of an upper-mantle rock composition is 1--4% less dense than seismic observations for temperatures between 2000--3000 K, suggesting distinct mantle layers not only based on structural phase changes but also chemical differences.;X-ray diffraction was also used to track the alloying behavior between two very different elements, alkali-metal potassium (K) and transition-metal iron (Fe) to test the theory of an alkali-to-transition metal electronic transition at high pressure as well as the theory of sequestering potassium into the Earth's iron-rich core thereby providing a long-lived radioactive isotope 40K to power the Earth's magnetic field and mantle dynamics. At pressures above ∼26 GPa and above the melting temperature of iron, K and Fe form an alloy in which one percent of the Fe atoms are substituted for K in the hexagonal-close-pack structure of epsilon-Fe thereby validating the former theory and making the latter possible.;Dynamic and static experimental methods were combined to explore the behavior of water at pressures above ∼50 GPa and up to ∼10,000 K. Water is found to exhibit complicated physical behavior---not surprising since at relatively low pressures and temperatures water has more than a dozen structures---with changing optical properties indicative of ionization and metallization with increased pressures and temperatures. |
