Philip Christensen

Dr. Phil Christensen is the 2018 recipient of the Whipple Award, the highest honor given by the Planetary Sciences section of AGU. Christensen is a leader in thermal infrared spectroscopy and radiometry who has contributed to technological developments for spacecraft missions and fundamental material science for the study of minerals and planetary surfaces.

Trained at the University of California, Los Angeles, Christensen’s first mission instrument was selected for the ill-fated Mars Observer and ultimately flown on Mars Global Surveyor. His instruments have been selected for eight missions to date, spanning exploration of the solar system from the asteroid belt to Jupiter.

Christensen has developed new techniques to infer the phases and relative abundances of minerals using carefully measured laboratory spectra of key minerals as end members. With instruments on two orbiters and two rovers on Mars, he has made multiple discoveries in the surface composition and near-surface physical properties. Ultimately, his instruments have provided global maps of the major compositional provinces on Mars and measurements of the seasonal cycles, temperature, dust, and water vapor in the atmosphere over multiple Martian years.

With his deep experience in planetary exploration, Christensen chaired the Mars panel in the last Planetary Science Decadal Survey and the National Academy of Science’s Committee on Astrobiology and Planetary Science. Christensen has demonstrated selfless leadership, and wisdom in his leadership, of the planetary community. Christensen’s deep impact on planetary science is also reflected in his dedication to teaching and training many students and postdoctoral researchers.

AGU honors Dr. Christensen for his fundamental contributions to exploration and discovery in planetary science.

—Sarah T. Stewart, University of California, Davis


I am deeply honored to receive this year’s Whipple Award. I’ve had the wonderful opportunity to participate in planetary exploration during its early phase of reconnaissance, when very little was known and almost every new observation led to a new discovery. Very early in my career I had the great fortune to work with Hugh Kieffer on the Mariner 9 and Viking missions to Mars. In addition to being and remaining a wonderful mentor and friend, Hugh introduced me to the excitement and satisfaction of being actively involved in planetary missions. I was privileged to be in a room with a group of remarkable individuals who were debating what we would see from the first images from the surface of another planet as Viking prepared to land in the early hours of 20 July 1976. It was also from Hugh that I, and several other of his students, developed an interest in building instruments and leading missions that could extend the boundaries of what we know about planetary surfaces and atmospheres. During my career, I have watched as Mars changed from a point of light in the night sky to a world that is becoming as familiar as our own. It is commonplace to look at vistas from Mars rovers and to address the same sophisticated questions that a geologist would ask when studying the geologic processes in the U.S. Southwest. It has been remarkable to watch planetary science advance to where we can now study all bodies in our solar system as unique worlds, with complex processes and histories of their own. One of the true pleasures of my career has been the opportunity to mentor students—I hope I’ve passed along some of what I’ve learned and helped to inspire the next generation of planetary explorers.

—Philip Christensen, Arizona State University, Tempe


(2018), Christensen receives 2018 Fred Whipple Award, Eos, 99, Published on 20 November 2018.

Text © 2018. The authors. CC BY-NC-ND 3.0
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