John Grotzinger is a field geologist interested in the evolution of Earth's surficial environments and biosphere. He is the Fletcher Jones Professor of Geology at the California Institute of Technology and serves as co-leader for strategic planning on the Mars Rover.

Tom Jordan is a geophysicist interested in the composition, dynamics, and evolution of the solid Earth. He is University Professor, W. M. Keck Professor of Earth Sciences at University of Southern California, and Director of the Southern California Earthquake Center.