Robert Grimm is a planetary geophysicist who has researched the interiors, tectonics, and thermal evolution of Venus, Mars, the Moon, asteroids, and icy worlds. He developed constraints on crustal thickness, heat flow, and lithospheric rheology using gravity, topography, crater relaxation, and thermal–mechanical modeling. He is a leader in contemporary low-frequency electromagnetic methods for probing silicates and H2O in planetary subsurfaces.  Grimm is the Principal Investigator of three lunar surface experiments: the Lunar Magnetotelluric Sounder (LMS, completed in 2025), the Rover Transmitter ground-penetrating radar (RTx, scheduled for flight in 2026), and the Lunar Interior Temperature and Materials Suite (LITMS, scheduled for flight in 2027). He enjoys linking theory, numerical modeling, and laboratory and flight measurements. Grimm received a B.A. from the University of Tennessee and a Ph.D. from the Massachusetts Institute of Technology.