McDonnell Center lecture on sampling the solar system

Distinguished physics alum returns to deliver Walker lecture, named for his former professor

Astronaut Edwin “Buzz” Aldrin standing beside the Apollo 11 solar wind detector. One of the goals of the Apollo missions was to understand the history of the sun in time. (Photo: NASA/Neil A. Armstrong)

Kevin D. McKeegan, a scientist whose analyses of meteorites and other materials from space has improved understanding of the processes and chronology of the early solar system, will deliver the Robert M. Walker Distinguished Lecture, sponsored by Washington University in St. Louis’ McDonnell Center for the Space Sciences.

Kevin D. McKeegan

McKeegan, a distinguished professor at the University of California, Los Angeles, and former chair of UCLA’s Department of Earth, Planetary, and Space Sciences, is scheduled to give the lecture at 7 p.m. Tuesday, Nov. 30, at Whitaker Hall, Room 100, on the Danforth Campus.

His talk, “Sampling the solar system: A key in our quest to understand Earth’s origin and evolution,” is free and open to the public, with in-person and Zoom viewing options. To register for the Zoom link, visit the McDonnell Center website.

McKeegan’s talk will offer a broad overview of the laboratory study of extraterrestrial materials brought back to Earth by space missions. He plans to describe the tools and techniques to analyze these materials and how this work is complementary to solar system exploration by robots and spacecraft — and soon, humans again.

“The origin of the Earth and moon are intimately related,” said McKeegan, who earned his PhD in physics in Arts & Sciences from Washington University in 1987, studying under the late Robert M. Walker and Ernst K. Zinner.

“The goal of all this research is to understand how a rocky planet like Earth is formed and whether it is more or less inevitable or if we need to have special circumstances to give rise to Earth-like planets. Are we really so special that we might be very rare in the galaxy?”

Investigating solar wind
Genesis collector array
Hexagonal collector array used to capture bulk solar wind on the Genesis mission. (Photo: NASA/JPL)

One of the goals of the Apollo missions was to understand the history of the sun in time. With no atmosphere or magnetic field to interfere, particles from the sun or the solar wind hit and became imbedded in the lunar surface. Many of the lunar sample studies were to determine the effects and characteristics of this solar wind.

To further investigate the solar wind, a special metallic glass collector was carried into space and exposed to the solar wind for 27 months on NASA’s Genesis mission. Among the analyses of materials returned to Earth were Kevin McKeegan’s analyses of oxygen isotopes, which determined the oxygen isotopic composition of the sun and solved a long-standing problem in cosmochemistry.

McKeegan, who describes himself as a child of the space age, believes that we are currently living in a golden age of space exploration.

“I was a kid during the Apollo days. Now as an adult and a professional, it’s amazing to me that I’m working on these materials that the astronauts brought back,” McKeegan said. “The upcoming missions are exciting and can be seen as part of this whole continuum. And maybe, in 10 or 15 years, we will even have samples of Mars back in terrestrial labs that will answer the question about whether there could be microbial life on Mars or not.”

McKeegan is part of Washington University’s Interdisciplinary Consortium for Evaluating Volatile Origins (ICE Five-O) team, led by Jeffrey Gillis-Davis, research associate professor of physics in Arts & Sciences. One of NASA’s Solar System Exploration Research Virtual Institutes, the ICE Five-O cooperative agreement, which is valued at more than $7 million, was announced in 2019.

Recognized by the National Academy of Sciences as a leader in the application of micro-analytical techniques to study meteoritic materials, McKeegan and his team at UCLA discovered that the oxygen isotopic composition of the sun is about 6% different from that of all rocky solar system bodies previously sampled, including Earth, the moon, Mars and asteroidal parent bodies of meteorites.

McKeegan and his colleagues accomplished this major discovery by analyzing samples from the Genesis space-probe mission, which collected particles from the solar wind.

When McKeegan was a graduate student at Washington University, his PhD adviser, Robert M. Walker, was among the first scientists to study Apollo samples of the moon and, in particular, the tracks left in lunar soil grains by solar wind particles.

According to Brad Jolliff, director of the McDonnell Center for the Space Sciences and the Scott Rudolph Professor of Earth and Planetary Sciences in Arts & Sciences: “McKeegan’s work years later on the Genesis mission samples of solar wind brings the research full circle to that of his adviser. Bob would have been very pleased to know that Kevin is giving the Robert M. Walker Distinguished Lecture.”

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