Research topics: (1) the study of crystal defects in minerals at the atomic level using high-resolution transmission electron microscopy, (2) the origin and character of carbonaceous chondrite and other meteorite types, and (3) the development and application of electron-beam instruments to the study of micro- and nano-particles in the atmosphere and their effects on air quality and climate,
1. Mineralogy/Solid State Geochemistry. High-resolution transmission electron microscopy (HRTEM) is extremely powerful for studying the chemistry and structure of crystalline materials. Microscopic irregularities and crystal defects in minerals can be observed and related to their geological histories. Chemical reactions, “frozen” while still in progress, can be observed and thus mechanisms of reaction understood. Of special interest are the complexities of order-disorder, non-stoichiometry, modulated structures, and other deviations from ideality in crystals. Development of methods for making high-pressure measurements within an electron microscope allows determination of hydrogen solubility in iron at elevated P and T for the study of the origin of terrestrial water.
2. Cosmochemistry. Carbonaceous and certain enstatite chondrite meteorites are among the most primitive materials in the solar system and contain the keys to many long-standing problems in cosmochemistry. Electron-beam instruments are used to study their mineralogy and geochemistry in order to understand the early history of the solar system.
3. Environmental/Analytical Geochemistry. Aerosol particles exert important effects on environmental quality, global climate change, cloud formation, and health. Electron microscopy and spectroscopy is used to analyze aerosol particles from around the globe to determine their chemical and physical properties. This research is done as part of international experiments involving ground-, ship-, aircraft-based, and remote-sensing satellite measurements in collaboration with scientists at government laboratories and other universities, with sampling campaigns in South Africa, Namibia, the Middle East, Japan, Europe, and the tropics.