Michael Francis A’Hearn

Michael Francis A’Hearn, a pioneer in the field of planetary science and comet research, the principal investigator of the NASA Deep Impact and EPOXI missions, and a recipient of the American Astronomical Society Division for Planetary Sciences Gerard P. Kuiper Prize, passed away at his home on 29 May 2017.

Born in Wilmington, Delaware in 1940, Mike received his BA from Boston College and his PhD from the University of Wisconsin, studying polarization of the atmosphere of Venus. An avid sailor and dedicated husband and father of three, Mike made seminal discoveries early in his career regarding dust, ice, and gas emitted from comets. By searching for signatures in the Jupiter Family comets in comparison with the Oort cloud comets, he identified signatures of chemical gradients in the solar system’s protoplanetary disk.

As a professor at the University of Maryland, Mike supervised numerous graduate students, many of them now prominent members of the field. With his acute grasp of physics and astronomy, he was a natural mentor for his students and colleagues. Mike’s first mission as principal investigator, Deep Impact, probed the subsurface material and directly tested the strength of the nucleus of the comet 9P/Tempel 1. The mission paved the way for future landers, including Rosetta, on which he served as co-investigator. Mike also was principal investigator of the extended mission repurposing of the Deep Impact spacecraft, which flew by the small but active comet 103P/Hartley 2; the probe measured the comet’s uncommonly high CO₂ production rate. Most recently, Mike was the principal investigator of the NASA Planetary Data System Small Bodies Node, overseeing hundreds of data sets from spacecraft and ground-based telescopes.

Mike was well-loved by his students, highly respected by the entire planetary science community, and will be greatly missed by his family, friends, and colleagues.