Scientist Who Studies How Planets Form Named MacArthur ‘Genius’ Fellow

The MacArthur Foundation has named Sarah T. Stewart, a planetary scientist at the University of California, Davis, who has developed novel theories about the formation of the Earth and moon, among the 2018 class of MacArthur Fellows. Sometimes known as the “Genius Grants,” the MacArthur Fellowship is a $625,000 award to extraordinarily talented and creative individuals as an investment in their potential. 

“It’s fitting that this prestigious no-strings-attached award goes to Professor Stewart because her curiosity and ingenuity know no bounds,” said UC Davis Chancellor Gary S. May. “I am thrilled for recognition this brings to her and our university community as a whole.”

Stewart is a professor in the UC Davis Department of Earth and Planetary Sciences, College of Letters and Science, who studies how planets form, developing new ideas about the evolution of the Earth and other planets. Her newly built Shockwave Compression Laboratory uses what are essentially mounted cannons to reproduce conditions reached during the violent collisions that form planets. The experiments fuel novel ideas into how the Earth and moon formed, and help scientists better understand planets outside our solar system.

The fellowship is awarded over five years and is a personal grant that the recipient can use however they see fit. Stewart said that while she does not yet have a specific project in mind, she hopes to use the funds for something “new and different.”

“I want to use it to enable something exciting that I haven’t had a chance to do yet,” Stewart said. 

Origin of the Earth and moon

Recently, Stewart and colleagues developed a new theory of the origin of the Earth and moon. Previous thinking held that the moon was stripped out of the Earth when another planet-sized object struck the Earth a glancing blow. But there are discrepancies between this model and the observed composition of the Earth and moon. 

Stewart and graduate student Simon Lock proposed instead that the Earth and moon formed from an entirely new kind of celestial object, a gigantic spinning donut of vaporized and molten rock that they call a synestia. They showed how a synestia could be created from a high-energy collision between two planet-sized objects with high angular momentum. 

“We are so pleased that Sarah Stewart is among the small cohort of 2018 MacArthur ‘Genius Grant’ recipients,” said College of Letters and Science Dean Elizabeth Spiller. “Sarah’s creative and distinguished scholarship enlarges the boundaries of what is possible; we are honored that the award recognizes the kind of curiosity-driven research and impact at the heart of everything we do in the college.”

Stewart received an A.B. (1995) from Harvard University and a Ph.D. (2002) from the California Institute of Technology. She was a professor at Harvard University from 2003 to 2014 before joining the faculty at UC Davis. 

Stewart is the third MacArthur fellow on the UC Davis faculty. The others are Professor Leah Krubitzer, Department of Psychology and Center for Neuroscience, and Geerat Vermeij, distinguished professor of paleobiology in the Department of Earth and Planetary Sciences, both in the College of Letters and Science. 

Media Resources

Sarah T. Stewart, Earth and Planetary Sciences, 530-794-8689,

Andy Fell, News and Media Relations, 530-752-4533,

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