Bjørn Mysen is intrigued with the chemistry and physics of the processes that govern the formation and evolution of the Earth and terrestrial planets, particularly the behavior of the properties of the materials involved. His primary focus is the physical chemistry of melting and crystallization at pressures and temperatures corresponding to the planetary interiors. This information is used to characterize energy transfer and transport processes there.

The physics and chemistry of the interaction between molten silicate (magma), its crystalline equivalent (igneous rocks), and water-rich fluids are central to his investigation. The common theme in these endeavors is to identify and link the structure of crystalline and molten silicate materials to their properties. These include thermochemical properties, element distribution between molten (magma) and crystalline (rock) silicate materials, and aqueous fluids. Additional aspects central to these investigations include transport properties such as viscosity of silicate melts and aqueous fluids, conductivity, and diffusion.

The behavior of materials like these are measured in the laboratory at high temperature (>1000EC) and pressure (Ž 1 GPa). Mysen examines their structural features on the atomic scale with the aid of spectroscopic methods such as vibrational, NMR, and Mössbauer spectroscopy. This approach requires examining silicate crystals, melts, and aqueous fluids while at the pressures and temperatures comparable to those deep within the planets. Physiochemical properties of these same materials are determined via a variety of chemical and physical methods, including microbeam and microscopic measurements together with thermochemical observations.

From the correlated experimental studies of structure and properties, Mysen developes models by which structural information is used to characterize the behavior of the properties relevant to rock-forming processes at high pressures and temperatures. This information in turn allows him to develop a framework to predict the processes of melting in planetary interiors, as well as the processes of aggregation, ascent, and crystallization of the silicate melts and aqueous fluids. This framework is required to understand the formation and evolution of the Earth and terrestrial planets.