It is with profound sadness we report that Dr. Michael J. Gaffey passed away on September 20, 2026 after a series of illnesses.
Mike was born December 1, 1945, in Meadville, Pennsylvania, and grew up on a farm in Iowa. His education began in a one-room schoolhouse, where he attended kindergarten through eighth grade. He graduated from Riceville High School in Riceville, Iowa in 1964. He initially studied astronomy at the University of Iowa before changing his major to geology, earning both bachelor's and master's degrees. In 1974, he received his PhD in planetary science from the Massachusetts Institute of Technology, where he remained as a research staff member for several years. He joined the University of Hawaii in 1977, first as a research astronomer and later in the Planetary Geosciences Division of the Hawaii Institute of Geophysics.
In 1984, Mike and his wife, Sue, moved to the Geology Department at Rensselaer Polytechnic Institute in Troy, New York. Their partnership, both personal and professional, was central to Mike's life, and Sue's unexpected death during their shared sabbatical in 1995 was a devastating loss. In the years that followed, Mike rallied with characteristic determination. He became a key co-investigator at the New York Center for Studies on the Origins of Life, a NASA Specialized Center of Research and Training. As astrophysicists, geologists, biologists, and chemists came together to investigate the origins of life, Mike served as an important bridge among these disciplines. His knowledge of planetary science and astronomy, combined with his skill in communicating across diverse disciplines, helped the group place meaningful constraints on the conditions of the early Earth under which life could become sustainable. He was part of an emerging scientific community that was helping to shape what would become the interdisciplinary field of astrobiology.
After retiring from Rensselaer in 2001, Mike joined the University of North Dakota, eventually becoming a full professor and interim chair in the Space Studies Department. At UND, he continued his research in asteroid spectroscopy while expanding his commitment to teaching and mentoring students. He brought to UND the same combination of scientific rigor, curiosity, and intellectual generosity that had characterized his years at Rensselaer. Mike was a pioneer in the development of a unique observational technique: sub-hemispheric spectral reflectance mapping of asteroids using ground-based telescopes. The technique requires long hours, perhaps even many nights, observing a single object as it rotates in order to obtain spectral data across its surface. Careful, quantitative analysis of absorption band parameters allowed Mike to derive mineralogical and petrologic relationships of geologic features on the surfaces of asteroids.
He used this technique of rotational spectral variations on a number of asteroids. The first published application was an analysis of asteroid 8 Flora 1. His results indicated that, among the S-type asteroids known at the time, and thought to be parent bodies of the ordinary chondrites, this particular S-type asteroid could not have been such a parent body.
Mike used his rotational spectral variation technique on a number of other asteroids, including 15 Eunomia2 , 3103 Eger3 (then known as 1982BB), 9 Metis and 113 Amalthea4,5, as well as 354 Eleonora6. Perhaps his two most famous efforts were with asteroids 4 Vesta and 6 Hebe, both of which were soon afterward bolstered by fortuitous events.
His rotational mapping analysis of Vesta7,8 indicated the likely presence and locations of large impact craters, as well as vast basaltic flows that were probably relatively pristine. These conclusions were confirmed later by Hubble Space Telescope imagery of 4 Vesta and by images and spectra obtained in 2011-2012 by NASA’s Dawn spacecraft mission to Vesta, on which Mike was a team member. It is still amazing to consider that such surface features could be identified through careful and comprehensive analysis of ground-based, unresolved non-imagery data.
Mike’s paper9 relating asteroid 6 Hebe to the H-type ordinary chondrites and Type IIE iron meteorites was initially controversial. Putting his spectral data into a 3-dimensional context allowed him to hypothesize the presence of a new type of ordinary chondrite, one not represented in any collection at the time. This hypothesis was greeted with much skepticism until a new type of ordinary chondrite, Portales Valley, fell in New Mexico in 1998. Analyses of Portales Valley10 matched the composition and petrology predicted in Mike’s earlier paper.
In 2006, Mike was recognized for his many outstanding scientific contributions with both the Leonard Medal from the Meteoritical Society and the G. K. Gilbert Award from the Geological Society of America. Those were followed in 2007 by the Thomas J. Clifford Faculty Achievement Award for Excellence in Research from the University of North Dakota Foundation. He was honored in 2008 by UND with an endowment as a Chester Fritz Distinguished Professor for his exemplary professional contributions that significantly advanced the teaching, scholarly activities, and service missions of the University.
Mike viewed his life in science and education not as a job or career, but rather a calling. His primary goal in his research was to produce the best science possible. He was proven superbly capable of this, as evidenced by his numerous highly-regarded publications and the deep respect he earned in the scientific community. Mike was always gracious and humble in accepting the awards he received. He maintained a philosophical conviction that carefully obtained and well-calibrated data should be the basis for all conclusions and that speculation should always be clearly identified as such.
Working for Mike as a graduate student was… interesting. Mike had an encyclopedic knowledge of wartime history, archaeology, paleontology, biology, movie trivia, science fiction novels, and a host of other topics. Winning a game of Trivial Pursuit against Mike (even double- teaming against him) was virtually impossible – the game is considered a contact sport in his family. He could discuss the economics of the farm tractor industry in eastern Europe (he grew up working on his family’s farm in Iowa) as easily as he could the muzzle velocities and best uses of various firearms (he was not the only marksman in his family). He conducted graduate-level classes about dinosaurs over pints of stout in a pub Among the graduate student populations at Rensselaer and UND, Mike was considered to “know everything,” and his office was where one went to seek literature resources.
Mike tended to hire “old and hairy” (his words) graduate students because they were self- motivated and did not require a lot of hand-holding. He said that non-traditional students with “real-world” experience were capable of networking and career building on their own, which he did not feel were his strong points. Regardless of their ages, Mike viewed his students as his academic children, and he generously invested in their efforts. His quiet reserve, coupled with his firm insistence on objectivity and thoroughness, often resulted in one being sent back to the lab with a stack of research papers to read for the week.
As an educator, Mike’s passion for sharing knowledge with students was unmatched. He was dedicated to developing effective approaches for teaching science to non-science majors. Students from a wide variety of backgrounds and disciplines enrolled in his courses because he was such a gifted teacher. His classes were always at capacity, and for the late straggler who attempted to sign up once the limit was reached, Mike would increase the maximum capacity. He refused to turn away a student who was eager to learn.
When his paper entitled The Early Solar System 11 was published, it was rumored that Mike was invited to write it because he had been around to witness the formation of the solar system. However, we have it on good authority from his family that Mike was born well after the formation of the asteroids. He did, however, begin his analytical observations of rocky planetary bodies at a much earlier age than most of his colleagues. According to Mike’s mother12, his very first spoken word was “shiny.” She said that Mike was looking up at the Moon at the time.
Tributes to Mike Gaffey can be posted on his CaringBridge page. Friends, colleagues and former students are welcome to contribute their memories, stories and photos of Mike.
1 Gaffey M. J. (1984) Rotational spectral variations of asteroid (8) Flora: Implications for the nature of the S-type asteroids and for the parent bodies of the ordinary chondrites. Icarus 60: 83-114.
2 Gaffey M. J., S. J. Ostro (1987) Surface lithologic heterogeneity and body shape for asteroid (15) Eunomia: Evidence from rotational spectral variations and multi-color lightcurve inversions. Lunar Planet. Sci. XVIII, pp. 310-311 (abstract).
3 Gaffey M. J., K. L. Reed, M. S. Kelley (1992) Relationship of E-Type Apollo Asteroid 3103 (1982BB) to the Enstatite Achondrite Meteorites and the Hungaria Asteroids. Icarus 100:95-109.
4 Kelley M. S. and M. J. Gaffey (2000), 9 Metis and 113 Amalthea: A Genetic Asteroid Pair, Icarus, 144(1): 27-38.
5 Gaffey M. J. (2002) Asteroid 113 Amalthea: Nature, origin and meteorite affinities of an S(I) assemblage. Icarus, submitted.
6 Gaffey, M. J., V. Reddy, S. K. Fieber-Beyer, and E. Cloutis, (2015). Asteroid (354) Eleonora: Plucking an odd duck. Icarus, 250, 623-638.
7 Gaffey M. J. (1983) The asteroid (4) Vesta: Rotational spectral variations, surface material heterogeneity, and implications for the origin of the basaltic achondrites. Lunar Planet. Sci. XIV pp. 231-232.
8 Gaffey M. J. (1997a) Surface lithologic heterogeneity of asteroid 4 Vesta. Icarus, 127, 130–157.
9 Gaffey M. J. and S. L. Gilbert (1998) Asteroid 6 Hebe: The probable parent body of the H-type ordinary chondrites and the IIE iron meteorites. Meteoritics & Planet. Sci., 33, 1281–1295.
10 McHone J. F., M. Killgore, and E. Killgore (1999) Portales Valley, New Mexico Fall of 13 June 1998: Anomalous Fragment Distribution and Composition, Lunar and Planetary Science Conference XXX, paper 1964.
11 Gaffey M. J. (1997b) The early solar system. Origins of Life and Evolution of the Biosphere - Special Astronomy Issue. 27, 185-203.
12 Personal communication to M. S. Kelley (1995).
Submitted by Michael S. Kelley, Vishnu Reddy, Sherry Fieber-Beyer, Peter Holden, Cathleen Donovan, and Kevin Reed.