David Stewart McKay, a career NASA planetary geologist whose work included controversial claims in 1996 that a four pound Martian meteorite recovered from Antarctica contained evidence of fossilized bacteria from the red planet, has died. He was 76.
McKay died in Houston on Feb. 20, following a lengthy illness. He joined NASA's Johnson Space Center in 1965. At his death, McKay was a chief researcher in astrobiology in Johnson's Astromaterials Research and Exploration Science Directorate.
David McKay. Photo Credit: LPI/HoustonIn his early years with the space agency, the Titusville, PA, native was instrumental in the training of the Apollo astronauts for their lunar excursions. He was a prime geology instructor for Apollo 11 commander Neil Armstrong and Buzz Aldrin, the lunar excursion module pilot. He was present in Mission Control during their July 20, 1969 moon walk as a resource.
The Martian fossil claims, published in the journal Science by McKay and his collaborators, followed studies of ALH84001, a Martian orthopyroxenite collected from the Allan Hills region of Antarctica in 1984. Though disputed by other scientists, the claim garnered global attention that helped to shape the objectives of NASA's current Mars program, including efforts by the Mars Science Laboratory/Curiosity rover to identify once-habitable environments suitable for microbial activity.
ALH84001, volcanic and silicate rich, was dated at 4.5 billion years, or almost to the formative period for Mars. Sometime between 3.6 and 4 billion years ago, ALH84001 was shattered by an impact that exposed it to water and conditions suitable for bacterial growth, McKay and his associates asserted. The specimen was liberated from Mars by an asteroid or comet impact about 16 million years ago with great force. About 13,000 years ago, it fell to Earth, landing in Antarctica, where it was recovered by a U. S. National Science Foundation team.McKay continued to pursue evidence for past life on Mars late into his career. His research interests included lunar soil, and space weathering as well. His work on the toxicity of lunar soil was to prepare for future human expeditions to the moon and Mars. His work in the development of planetary simulants led to a patent for their use in toxic waste purification.