NSF-BSF Application: Research on Reaction between H2-H2O Fluid and Silicate, and Implications for Uranus and Neptune

The giant planets (Jupiter, Saturn, Uranus, & Neptune) contain more than 99% of the mass in the solar system except for the Sun. However, our understanding of the composition and the interior of these planets is still limited. While Jupiter and Saturn contain mainly hydrogen (H) and helium (He), Uranus and Neptune have thinner H-He envelopes, making them key to understand the structure and the composition below the gas envelope in the context of planet formation and origins of the solar system. This project will systematically map fluid-silicate interactions over an array of pressure, temperature, and H2/(H2+H2O) ranges, and then couple the experimental results with interior evolution models to understand the formation of Uranus and Neptune. This project will provide a unique collaborative research opportunity between mineral physics and planet evolution theory for an undergraduate researcher and a postdoctoral researcher, training early career scientists in multi-disciplinary research that is particularly relevant to exo-planet science. Recent pilot experiments found that H2/H2O ratio influences fluid-silicate reactions and therefore this ratio is key for understanding the interiors of Uranus and Neptune. Even though the pressure expected for the region (10–200 GPa) is accessible in experiments, little is known about the behavior of materials in various H2-H2O rich conditions. This project will experimentally measure reactions between H2-H2O fluid and silicates at high pressure -temperature conditions and will determine how the metallization of hydrogen and the superionicity of H2O above 100 GPa can change the fluid–silicate reaction. The experimental results will be coupled with planetary interior evolution models to characterize the composition profiles and thermal evolution of Uranus and Neptune. Results from this project will also benefit the exoplanet community by develop a more thorough understanding of the behavior of materials and reactions realistic for sub-Neptune exoplanets. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.