2019 G. K. Gilbert Award

Presented to Alfred McEwen

Alfred McEwen

Alfred McEwen
University of Arizona


Citation by Jeffrey M. Moore, NASA-Ames Research Center

It is a tremendous pleasure to see Alfred McEwen presented with the G.K. Gilbert Award. Alfred has made substantial contributions to Solar System geology for decades, and he continues to be at its forefront today. Alfred first gained the attention of our field in the early 1980s, soon after he returned from stints with the Peace Corps and the Soil Conservation Service, with the production of very carefully calibrated color, or colorized, large mosaics of Io and Mars. These large color mosaics became iconic. They are still among the most widely used global representations of these worlds. In addition to their beauty, they were used to map out compositional variations across their surfaces. By the 1990s Alfred was an Interdisciplinary Scientist on the Galileo mission and was deeply involved in the planning and coordination of multi-instrumental observations of Io and the other Galilean satellites. This work led to his recognition of ultramafic komatiite-like eruptions as well as both silicate and sulfur lava lakes and flows. He subsequently summarized our current understanding of Io’s volcanism and tectonism in a series of multidisciplinary papers that still remain seminal. 

In the early 2000s Alfred designed and proposed an ultra-high resolution camera for the study of Mars from orbit which became the High Resolution Imaging Science Experiment (HiRISE) on Mars Reconnaissance Orbiter, which remains the backbone of Mars geological studies to this day. The images from HiRISE have proven to be crucial for the on-going exploration of the planet. The Curiosity rover uses them every day to design its traverses across Gale crater, as did the two Mars Exploration Rovers. Almost every paper now published on martian geology is illustrated with HiRISE images. Alfred’s own work with these data can be exemplified by his study of (1) the number and distribution of secondary craters from a primary (an important consideration in the determination of crater ages from small impacts); and (2) recurring lineae and their possible triggering by deliquescent salts, and the implication these features have as indicators of the intermittent presence of liquid water at the surface.

Alfred has been a conscientious and diligent member of our scientific community, having served on conference organizing committees, editorial boards, as well as several NASA Committees, including, until recently, Chair of the Outer Planets Assessment Group, and on the National Academy of Science Decadal Surveys for Planetary Science. Last year he co-convened a Keck Institute of Space Studies workshop on Tidal Heating, making an argument for future missions to Io. Alfred is booked solid with ongoing missions, in addition to his leadership role on HiRISE, he is a Co-Investigator on the CaSSIS camera aboard Mars Trace Gas Orbiter, and the LROC camera on Lunar Reconnaissance Orbiter.  He is also Co-investigator on upcoming the Europa Clipper’s main mapping camera. Everyone who has had the good luck to know and work with Alfred has experienced his great enthusiasm for exploration, his zest for discovery, his wonderful artistic sense of aesthetics as revealed in even his earliest efforts, and his generosity in collaborating and, then training, two generations of planetary geoscientists. It is a great personal pleasure to be able to regard Alfred, since our graduate school days, as a dear friend, and to now see him so justly honored with the Gilbert Award.


Response by Alfred McEwen

Thank you, Jeff, for that awesome citation. It seems fitting since you were last year’s G.K. Gilbert award recipient and that we were fellow graduate students at nearby ASU.  

I’m thrilled to see my name added to a list that includes my most important early mentors: Larry Soderblom and Gene Shoemaker from USGS in Flagstaff. Studying multiple satellites and planets (including Earth) came naturally based on their examples. I was fortunate to be hired as an undergraduate by Larry plus Hugh Kieffer at USGS in spite of zero qualifications; I also thank Ronald Reagan--the newly elected president who promised to freeze future Federal hiring. 

I got addicted to planetary missions as a student, processing new Voyager and Viking images, and seeing how new missions were conceived and developed. The Voyager 2 Uranus and Neptune encounters were incredible. My favorite world was always Io, and I was fortunate to be invited to replace Hal Masursky on the Galileo mission soon after the spacecraft finally launched. Joining Shoemaker on the Clementine mission to the Moon was my first chance to participate in developing a mission from its early stages, although very different from how NASA operates today. When Clementine first went into lunar orbit and we were anxiously awaiting the first data in Alexandria, Mike Belton, the Galileo imaging team leader, sent out a partial image showing that asteroid Ida had a satellite. I blurted out “wow—look at this” to those in the room, which then got to NASA HQ people before Mike could announce the discovery to them. He was not at all pleased! I fessed up, and instead of throwing me off the team he immediately said “okay, let’s put that behind us” and even made me the lead for Io imaging. That was a great example to me later, as HiRISE PI. 

After two unsuccessful Mars orbiter instrument proposals, the MRO opportunity appeared in 2001. I met Alan Delamere at Ball Aerospace during a 1999 Europa Orbiter proposal, and he had a great concept for MRO. My Deputy-PI Candy Hansen came up with the name of HiRISE. We had less than 3 years from selection to delivery for an instrument with significant development challenges, something that NASA no longer attempt. Achieving the processing speed nearly killed it, and us. There are now over 1500 peer-reviewed papers using HiRISE data. 

Getting back to Io and the Jupiter system is what I most want to do, and I have the honor of being Zibi Turtle’s Deputy-PI for EIS on Europa Clipper. I’m also PI of the Io Volcano Observer proposal to Discovery, which is the main item on my bucket list.

I’d like to thank other major collaborators: Torrence Johnson, Dennis Matson, Jonathan Lunine, Ron Greeley, Mike Malin, Eric Eliason, Carle Pieters, Jim Head, Mark Robinson, Paul Geissler, Mike Carr, John Spencer, Laz Kestay, Ashley Davies, Jen Grier, Bob Pappalardo, Peter Thomas, Rosaly Lopes, Sue Kieffer, Cynthia Phillips, Moses Milazzo, Chris Okubo, Jani Radebaugh, Devon Burr, Ross Beyer, Phil Christensen, Windy Jaeger, Colin Dundas, Maria Banks, Matt Golombek, Randy Kirk, Shane Byrne, Veronica Bray, Serina Diniega, Nick Thomas, Ingrid Daubar, Luju Ojha, Sarah Sutton, Beau Bierhaus, Livio Tornabene, Nathan Bridges, Donna Viola, Matt Chojnacki.