Dr. Thomas H. Prettyman has done repeated seminal work in the application of neutron and gamma ray spectroscopy to determine the elemental composition of planetary surfaces. He has been instrumental in the success of a number of flight instruments that determined the elemental composition of the Moon, Mars, Vesta, and Ceres. His paper interpreting the gamma ray spectra from the Lunar Prospector orbiter provides the most complete remote sensing measurement of elemental (Fe, Ti, K, Mg, Al, Ca, Si) abundances and distributions on the Moon to date and identifies distinct regions of heightened radioactive heating. His resulting 2006 publication is a classic in the discipline. He has also been instrumental in the mapping of hydrogen distributions on Mars and the Moon, which have been critically important in unraveling the history of water on those bodies. As a coinvestigator on Mars Odyssey, Tom led a study that determined the reservoirs of CO₂ on Mars. He served as principal investigator for the Gamma Ray and Neutron Detector (GRaND) instrument on the Dawn asteroid orbiter. Tom designed and built GRaND and operated it to great advantage in studying Vesta and Ceres. The first analyses of Vesta, published in Science in 2012, provided strong evidence that this asteroid is the parent body for the HED (howardite-eucrite-diogenite) igneous meteorites, and data from this instrument allowed Tom to map the global distributions of igneous rock types and to bolster interpretations of Vesta’s magmatic differentiation. His work also prompted the unexpected discovery of hydrogen in its regolith, water delivered by exogenic carbonaceous chondrite. Tom’s interpretation of Ceres’s gamma ray and neutron spectra revealed latitudinal variation in subsurface water ice content. The elemental abundances also provide a linkage with carbonaceous chondrite, although we have no meteorite samples from Ceres. This dwarf planet has become astrobiologically interesting, in part a result of GRaND’s data on carbon and hydrogen. Tom continues to push our science forward, designing a muon detection system and method to take advantage of muons produced by high-energy galactic cosmic radiation on the surface of small asteroids and comets to construct tomographic maps of their interiors, the physical structures of which are otherwise unconstrained by data. Tom is also passionate about sharing scientific discoveries with the public and has contributed to science, technology, engineering, and mathematics (STEM) education for Native American communities in New Mexico, where he lives.

—Mark Sykes, Planetary Science Institute, Tucson, Ariz.

I am grateful to the AGU Planetary Sciences section for recognizing me with the Fred Whipple Award. I am proud to be among those to have received this honor. My contributions were part of team efforts spanning several NASA missions and programs. I’m fortunate to have had the opportunity to work with the many talented scientists, engineers, and support staff who made these missions possible. This award belongs to them, too, and I only wish I could recognize everyone who made a difference here. My path to a career in planetary science was through nuclear engineering, which provided a solid foundation in instrument design, modeling, and data analysis. I had a brief introduction to geology by way of graduate and postdoctoral work developing tools for geophysical logging. I thank my doctoral advisers at North Carolina State University for helping me get my start. An early career in nuclear safeguards at Los Alamos National Laboratory, with support from strong mentors, sharpened my skills. Adventures in space and planetary science began at Los Alamos with Lunar Prospector, which led to my participation on Mars Odyssey, Dawn, and beyond. The Lunar Prospector team promoted a culture of open—and often spirited—exchange of ideas and information, which led to some amazing discoveries. The same culture permeates planetary science, and collaborations with the members of the planetary community were essential to the work recognized by this award. Joining the Planetary Science Institute enabled me to focus my efforts on Dawn and to make forays into new areas, including the muon studies cited as well as field geology. The importance of a welcoming and supportive home institution cannot be overstated. My STEM education and outreach efforts benefited from collaborations with fellow New Mexicans from several organizations, including the Institute of Meteoritics at the University of New Mexico, the New Mexico Museum of Natural History and Science, the Albuquerque Astronomical Society, and Sundance Educational Consulting. Finally, I am grateful to my parents, who nurtured my early interests in science and engineering, and my lovely partner, Sandra, as well as friends and family who supported me along the way. I dedicate this award to my son Michael and all those lost in the pandemic. My hope for colleagues is that they find a way to prioritize time with their families ahead of work. —Thomas H. Prettyman, Planetary Science Institute, Tucson, Ariz.