Carnegie Fellow Nick Schmerr joined DTM in September after receiving his Ph.D. at Arizona State University. His research focuses on seismological observations pertinent to the thermo-compositional state of the Earth's interior. In particular, he studies the seismic structure of the 410-km and 660-km upper mantle discontinuities that delineate increases in mantle density and seismic wave speeds in the Earth. These boundaries arise from solid-state phase changes in the mineral olivine, and lateral variations in mantle composition and temperature give rise to topography on the discontinuities, making them an ideal probe of Earth’s structure. Schmerr’s dissertation research was an investigation of thermal and chemical heterogeneity beneath the South American subduction zone, as well as thermal variations in the mantle beneath the Pacific Ocean, from upper mantle discontinuity topography. At DTM, Schmerr plans to continue mapping the structure of these discontinuities around the globe and to develop several new observational techniques to interrogate their structure at shorter wavelengths. He is also interested in developing seismic models of the interiors of other planets and moons, on the basis of their expected compositions, to seek clues to the thermal and chemical evolution of these bodies.