Professor Walker, colleagues and students at the University of Maryland Isotope Geochemistry Laboratory conduct research in several areas of Earth and planetary science. These study areas include: 1) the chemical structure and evolution of the Earth's mantle, particularly with respect to the behavior of highly-siderophile elements (including: Re, Os, Ir, Ru, Pt, Pd) and moderately siderophile elements (including: W and Mo), 2) the accretionary and crystallization histories of early solar system planetesimals, with current emphasis on early condensates, core formation timing and processes, and final stages of planetary accretion, and 3) the differentiation histories and chemical evolution of Earth, Moon and Mars.

The research program involves both students and research scientists, and has also included the participation of numerous visiting scientists from the U.S. and abroad. The bulk of this research is accomplished using the facilities of the Isotope Geochemistry Laboratory. Current work in the lab includes the measurement of the ¹⁸⁷Re-¹⁸⁷Os, ¹⁹⁰Pt-¹⁸⁶Os, ^147,146Sm-^143,142Nd, ⁸⁷Rb-⁸⁷Sr and ¹⁸²Hf-¹⁸²W radiogenic isotope systems, and high precision Pt, Os, Ru and Mo isotopic measurements for genetic tracing of cosmochemical materials and cosmic ray exposure dosimetry.