Candice Hansen-Koharcheck, a Planetary Science Institute senior scientist since 2010, died on April 11 after a valiant three-year battle with cancer. Her career spanned nearly 50 years, during which she authored more than 300 journal articles on topics from erupting jets on Triton and Enceladus, to outer planet satellites’ tenuous atmospheres, to carbon dioxide processes on Mars. She played a critical role in many high-profile NASA missions including Voyager, Cassini, Mars Reconnaissance Orbiter, Juno and Europa Clipper. She is remembered by her colleagues as endlessly kind and supportive, with a talent for mission operations and team coordination. She is also regarded as a trailblazer at a time when there were few women in planetary science.
Hansen-Koharcheck was born in Pasadena, Calif. In 1976 she earned a B.S. in Physics from California State University, Fullerton, where she was inspired to become a planetary scientist by Dorothy Woolum, who worked on the Apollo program. She then began a short stint in graduate school at the University of Arizona. Under the mentorship of Bradford Smith, who led Voyager’s imaging team, she was encouraged to leave Tucson to begin work at NASA’s Jet Propulsion Laboratory on Voyager as assistant experiment representative. Her task was to design the camera images for every satellite flyby that occurred during Voyager’s encounters with Jupiter, Saturn, Uranus and Neptune. In 1981, she earned the NASA Individual Achievement Award for this work.
From 1981-84, during the long cruise period between the Saturn and Uranus encounters, she worked at the German Space Operations Center in Oberpfaffenhofen on the Ion Release Module, the German portion of the Active Magnetospheric Particle Tracer Explorer, a multinational Earth orbiting mission designed to study the Earth’s magnetosphere.
She returned to Voyager for the Uranus flyby in January 1986. In 1987, Hansen-Koharcheck returned to graduate school, this time at UCLA. Two years later, while preparing for Voyager’s Neptune encounter, she finished her Master of Science in Planetary Physics, and in 1994, completed her doctorate in earth and space science. Her dissertation included a thermal model of Triton’s nitrogen frost and atmosphere, based on Voyager data. She has also applied the thermal model to Pluto and other Kuiper Belt objects.
In 1990, Hansen-Koharcheck began working on NASA’s Cassini-Huygens mission to Saturn with the Ultraviolet Imaging Spectrograph (UVIS) investigation team, and was responsible for planning and analyzing UVIS icy satellite data. In 2002, she earned an Exceptional Leadership Award from JPL for her science planning efforts for Cassini’s Jupiter flyby observations. She remained a UVIS co-investigator until 2017, when the spacecraft was retired. She led several papers analyzing UVIS data of Enceladus’ water vapor plume. In 2009, she earned the NASA Exceptional Scientific Achievement Medal for this work. She was also the deputy principal investigator on the Mars Polar Lander payload from 1994-99, when the spacecraft was lost.
In 2010, Hansen-Koharcheck retired from JPL and continued her work at the Planetary Science Institute.
At the time of her death, Hansen-Koharcheck was deputy principal investigator emeritus for the High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter. Her research focused on the seasonal carbon dioxide polar cap of Mars. She also pursued that interest as a co-investigator on the High-resolution Stereo and Color Imager (HiSCI) flying on the Mars Trace Gas Orbiter. Hansen-Koharcheck was also a co-investigator on the Juno mission, which has been in orbit around Jupiter since 2016. On Juno, she was responsible for the development and operation of the JunoCam outreach camera designed to engage the public in planning and processing images of Jupiter and its satellites. For this work, she earned the NASA Outstanding Public Leadership Medal in 2018 and NASA Exceptional Public Service Medal in 2023. Hansen-Koharcheck continued her adventure at Jupiter as a co-investigator on the Europa Imaging System (EIS) on the Europa Clipper mission, scheduled to arrive in the Jupiter system in April, 2030.
In addition to the many awards and honors throughout her career she received the Geological Society of America’s G. K. Gilbert Award for contributions to Planetary Geology in 2023. She also served as the Chair of the NASA Outer Planets Assessment Group and Chair of the Division for Planetary Sciences of the American Astronomical Society.
Robert “Bob” Carlson died peacefully in his sleep in Reno, Nevada, surrounded by family, after a months-long battle with cancer. Bob was a brilliant scientist, as well as an amazing mentor, friend, husband, father, and grandfather. Those of you who knew him likely recall fond memories of his soft, but detailed approach to any problem – always gracious and insightful. He was born in Waseca, Minnesota, graduated from Cal Poly San Luis Obispo in 1963, and received his PhD in physics from the University of Southern California in 1970. Bob spent most of his career (1978-2016) at the Jet Propulsion Lab in Pasadena, California. As Principal Investigator of the Galileo Near Infrared Mapping Spectrometer (NIMS), he was also the greatest skeptic of the results. Among many firsts made by Bob and the NIMS team, the discovery of hydrogen peroxide and a radiolytic sulfur cycle on Europa have transformed our understanding of the potential habitability of that world, and have helped set the stage for future exploration. As an AGU Fellow and Editor-in-Chief for the Journal of Geophysical Research – Planets, he worked hard to see the best in every manuscript. In the lab, Bob was meticulous and diligent, enjoying every opportunity to solve a new planetary puzzle. He is survived by wife Kathie, sister Jeanne Withroe, his two daughters Jill Carlson and Kristen Conway, and his four beloved grandchildren Noah, Bridget, and Caleb Conway, and Cooper Carlson.