Liquid water is essential to life, and the search for habitable planets within our solar system and elsewhere in the galaxy has come down to a search for planets on which liquid water can exist. Earth is a water planet, but how the Earth acquired its water is a subject of intense debate, measurement, experiment, and theoretical calculation. There are not yet solid constraints on how much water the Earth has, because the components of water, atoms of hydrogen and oxygen, are incorporated into the solid silicate minerals of the interior, and this water can be exchanged with the surface reservoir over the long stretch of geologic time. This is an experimental research project to measure the solubility of hydrogen in the solid, oxygen-based silicate minerals of the deep interior of the Earth in order to place some constraint on how much hydrogen the planet can harbor in this region which constitutes more than half the mass of the planet. The mineral crystals, which are quenchable, will be grown at high pressure and temperature, and their physical properties (density and seismic velocity) will be measured. The principal objective is to constrain the amount of water (hydrogen plus oxygen) that can be stored in the interiors of Earth-like planets, and how this may affect the dynamics of the deep interior.
This is a project to synthesize and characterize hydrous magnesium silicate and oxide phases thought to be stable in Earth's interior at depths of 600 to 2900 km. In collaboration with other research groups, principally in Germany, the investigators have synthesized samples of MgSiO3 in several different crystal structures under hydrous conditions with various minor substituents, principally aluminum and iron. They have found significant solubility of H in akimotoite (ilmenite-structure), majorite (garnet structure), and in aluminum-bearing perovskite. This project renewal is to focus on H solubility in aluminous perovskite. MgSiO3-perovskite is thought to be the most abundant mineral in the interior and potentially the largest reservoir of H in the planet. Synthesized high pressure minerals will be analyzed for crystal structure, chemical composition and hydrogen content. Measurements of elasticity will be made in order to constrain the effect of hydration on seismic velocity. The data obtained should permit a greater understanding of the crucial role of hydrogen in mantle dynamics and further constrain the amounts of hydrogen that may be stored in the interiors of Earth-like planets.
