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 recipient of the American Astronomical Society Division for Planetary Sciences Gerard P. Kuiper Prize, passed away at his home on Sunday, May 29, 2017.

Born in Wilmington, Delaware in 1940, Mike received his Bachelors of Arts in Science from Boston College and his PhD from the University of Wisconsin, studying polarization of the atmosphere of Venus. An avid sailor, husband, and father of three, Mike made seminal discoveries regarding dust, ice, and gas emitted from comets early in his career. By searching for signatures in the Jupiter Family comets in comparison to 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, he supervised numerous graduate students, many of them now prominent members of the field, and with his acute grasp of physics and astronomy, was a natural mentor for his students and colleagues. Dr. A’Hearn’s first mission as principal investigator, Deep Impact, probed the sub-surface material and directly tested the strength of the nucleus of the comet 9P/Tempel 1, paving the way for future landers on cometary surfaces, like with the Rosetta Mission, on which he would serve as co-Investigator. Mike A’Hearn 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, measuring its uncommonly high CO2 production rate. Most recently, Mike A’Hearn 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 A’Hearn 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.