When NASA’s Galileo spacecraft reached Jupiter in 1995, Margaret Kivelson was on the brink of a revolutionary discovery: Earth is not the only ocean world in our solar system. By studying magnetic field data, Kivelson demonstrated that Europa, an icy moon, conducts electrical currents induced by Jupiter’s magnetosphere—a surprising phenomenon that could only be explained by the presence of an unexpected ocean beneath the moon’s frozen surface. Through this discovery and a host of others, over decades of groundbreaking work with NASA and the European Space Agency (ESA), Kivelson has changed the way we think about the outer reaches of the solar system and the possibility of life beyond Earth.

“Margy’s discovery of Europa’s subsurface ocean is one of the most important discoveries in the history of planetary science,” says Hao Cao, a research associate in the Bloxham Group at Harvard and one of Kivelson’s collaborators. “This was the first definitive detection of a liquid saltwater ocean anywhere other than planet Earth. Like many important discoveries, it opened new doors and pointed towards exciting new possibilities.” 

Kivelson, a distinguished professor of space physics emerita at the University of California, Los Angeles, and research professor at the University of Michigan, did not start out as a space scientist. She studied physics at Radcliffe College as a member of the Class of 1950 and stayed on at Harvard to complete her PhD in 1957, studying quantum electrodynamics under the mentorship of Nobel Prize–winning physicist Julian Schwinger; she was the only woman he advised. Kivelson began her career at the RAND Corporation in Santa Monica, California, and returned to Harvard in 1965 through a visiting fellowship at the Radcliffe Institute for Advanced Study. After her fellowship year, she secured an appointment as an assistant research geophysicist at UCLA, where she shifted her focus to space physics and was named a full professor in 1980. She later chaired the Department of Earth and Space Sciences and the Chancellor’s Advisory Committee on the Status of Women, served as president of the Association of Academic Women at UCLA, and encouraged the university to establish one of the first women’s studies programs in the nation.

Kivelson’s service to Harvard has been equally exceptional. She was a member of the Board of Overseers of Harvard College from 1977 to 1983 and received a Harvard Medal in 1986 as part of the University’s 350th anniversary celebration. “Margy has been a very loyal alumna and supporter of Harvard,” affirms Michael McElroy, Gilbert Butler Professor of Environmental Studies and founding chair of the Department of Earth and Planetary Sciences. He remains grateful for Kivelson’s guidance as chair of the first Visiting Committee to the department when it formed in the 1980s. “Margy was very generous with her time in coming to what was basically a new department,” McElroy says. “She made sure that we were doing the right kinds of things in the early stages.”

Earlier in her career, Kivelson co-edited Introduction to Space Physics, still the most widely used textbook in the field, and helped shape the future direction of scientific inquiry as chair of the Advisory Committee to the Division of Atmospheric Sciences of the National Science Foundation. Today, she serves as chair of the Space Studies Board of the National Academies of Sciences, Engineering, and Medicine—responsible, among other things, for conducting a decadal survey that will assess key questions in planetary science and astrobiology, identify priority space missions, and present a comprehensive research strategy for the coming decade. 

Thanks to Kivelson’s work, research into the magnetic fields of planets and moons has led to some of the most important and unexpected discoveries in planetary science. “There are a lot of surprises out there, which is what makes this science so exciting,” says Jeremy Bloxham, Mallinckrodt Professor of Geophysics. “When Margy showed that Europa has a subsurface ocean, that really changed the way we think about the solar system, and in particular the question of where there might be life in the solar system. The focus had been on Mars, but her discovery of the subsurface ocean on Europa just grabbed everybody’s attention. It was a stunning finding.”

Kivelson’s work in this area continues, more than 60 years after she earned her PhD: she is leading the magnetometer team on NASA’s upcoming Europa Clipper mission, which will investigate whether the moon could be hospitable to life, and participating in ESA’s Jupiter Icy Moon Explorer (JUICE) mission. “It’s unprecedented for somebody to be as active as Margy is at her stage of her career,” Bloxham says. “What is particularly nice about her involvement with Clipper and JUICE is that it’s precisely because of her earlier work that we’ve come to realize just how interesting Jupiter’s moons actually are. It’s really quite remarkable: she is still as active as she has ever been.”

Margaret Kivelson, for your pioneering achievements and discoveries in space physics, including your detection of ocean worlds in the outer reaches of our solar system, and for your stalwart leadership of programs and space missions that will shape the future of planetary science, we are proud to award you the 2020 Centennial Medal.

Read about the 2020 Centennial medalists

Margaret Kivelson: 2020 Centennial Medal Citation

Photo by Pamela Davis