Jacobsen is a mineralogist who studies the high-pressure physics and chemistry of minerals, glasses and melts in various applications to Earth and planetary science, chemistry, and materials science. Mineral physics utilizes an atomic-scale understanding of composition, structure, and physical properties of materials to interpret global-scale geophysical processes, geochemical cycling, and to investigate potentially useful properties of minerals and new materials for societal applications. Jacobsen is especially interested in the role of water in minerals on the origin and distribution of water in the Earth. In chemistry and materials science, he uses extreme conditions of pressure and temperature to explore new phase space in the design and synthesis of functional materials including superhard materials, novel intermetallics, and materials for operation in extreme environments. Jacobsen currently serves on the Executive Committee of NSF-COMPRES, the Committee for Seismology and Geodynamics at the National Academy of Sciences, and is Associate Editor of Geophysical Research Letters.