Planetary scientist Sarah Stewart will deliver the 2023 McDonnell Distinguished Lectures on her game-changing theory on the origin of the Earth and Moon.
The solar system as we know it represents the aftermath of billions of years of collisions, large and small. Sarah Stewart, professor of earth and planetary sciences at the University of California, Davis, uses lasers, high-powered gas guns, and computer models to simulate collisions of planetary materials. Her insights have changed the way researchers think about the origin of the Earth, our Moon, and other celestial bodies.
Stewart will deliver the 2003 McDonnell Distinguished Lectures, starting with a scientific colloquium on March 1 titled “Can collisions create Earth’s isotopic cousin?”. On March 2, she will deliver the public lecture “Rewriting the creation story for the Earth and the Moon.”
Stewart, who attended high school in O’Fallon, Illinois, said she’s looking forward to returning to the area. “I knew about the great science at WashU and the McDonnell Center for the Space Sciences when I was in high school, so it’s very exciting to present my work in this lectureship,” she said.
The public lecture should appeal to the large community of space enthusiasts in the St. Louis area, said Bradley Jolliff, the Scott Rudolph Professor of Earth and Planetary Sciences and director of the McDonnell Center for the Space Sciences. “I’ve seen her at many conferences and she gives a spectacular presentation,” he said.
The science behind each of Stewart’s talks represents the cutting edge of planetary origin theory. “Professor Stewart designs unique experiments to determine the fundamental properties of planetary materials,” Jolliff said. “Indeed, she has established a new paradigm for the formation of the Earth-Moon system.”
Stewart has proposed the existence of “synestias,” hypothetical celestial objects that could explain many characteristics of the Earth and Moon. Stewart described synestias as “giant donuts of vaporized rock” that form when planet-sized objects collide. The result is a rapidly spinning mass of molten rock and rock vapor. If our own planet started as a synestia, Stewart posits, the chunks of molten rock that were ejected from the impact could have formed the seeds for the Moon.
Such a scenario would explain why the Earth and Moon share nearly identical isotopic fingerprints. It would also explain why the Moon contains only trace amounts of hydrogen. Stewart estimates that the Moon formed in Earth’s synestia at a temperature of 3,000 to 4,000 degrees Fahrenheit, heat that would have vaporized almost all of the hydrogen and other volatile elements.
In 2018, Stewart won a MacArthur Foundation “genius grant” for her work on planetary formation. She has also received the Urey Prize from the American Astronomical Society’s Division for Planetary Sciences and the Presidential Early Career Award for Scientists and Engineers. In 2019, she delivered the widely-viewed TED Talk “Where did the Moon come from? A new theory.”
Jolliff said the public lecture will offer attendees a compelling introduction to a breakout concept in planetary evolution. “Right now, her theory is the best thing going,” he said.