Ralph Milliken

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Ralph Milliken
Assistant Professor of Geological Sciences
Mike Cohea/Brown University
A Brown alumnus is coming back to Providence to continue his quest to trace water’s history and role across the solar system. This fall he’s following the progress of the Mars rover Curiosity, as it examines the geology of its landing crater — a location that Milliken helped NASA select.

Ralph Milliken is a new assistant professor of geological sciences, but don’t look for him on campus until Thanksgiving time. From now until then he’ll be at NASA’s Jet Propulsion Lab in Pasadena and his mind will be on Mars.

That’s because he is part of the science team for the newly landed Mars Science Laboratory. Milliken, who studies the role and distribution of water throughout the history of the solar system, helped to pick the Gale Crater as the landing site. The MSL rover, nicknamed “Curiosity,” will look for water and for organic material in the crater’s soils and rocks.

“There were ultimately four finalist landing sites that were in the running and every one of them was great,” he said. “The reason the Gale Crater site won out is because it displays a great diversity in the appearance and morphology and mineralogy of the rocks. You have a 150-km diameter crater and in the middle you have this giant mound of rocks that is 5 km tall. You have more rocks exposed in this mound than you do in the Grand Canyon.”

There are even clay minerals there that required water to form, he said, and some scientists argue that such clays were also instrumental in the origin of life on Earth. The nuclear-powered rover will charge up the mound, starting with the oldest rocks on the bottom and finding progressively newer ones as it climbs.

The rover provides an exciting new opportunity for Milliken’s research, but his interest in solar system water, which is essential for life, literally and figuratively reaches far and wide. Where is the water? How has that changed over time?

“A lot of that has focused on Mars,” he said. “But I’m also interested in broader questions about water and its role on our planet and beyond. So, I’m interested in water on the Moon or on asteroids — how it got there, how much there is, and what role it has played in the evolution of those bodies.”

To find answers to these kinds of questions, he uses data not only from rovers, but also from “remote sensing” telescopes and satellites, which train their specialized gaze upon planetary bodies and asteroids from afar and then analyze the reflected light for the chemical signatures of materials on the surface.

Milliken began asking these questions in earnest when he came to Brown as a master’s student a decade ago and then in his doctoral studies. First he set out to study Martian surface features that appeared to have been carved by an ancient flowing liquid. With adviser Jack Mustard, professor of geological sciences, he then investigated a particular remote sensing spectroscopy technique that could be used to determine the water content of various rocks and minerals. He wanted to improve the technique enough to make quantitative estimates of water on the soils of the Moon and Mars. Looking back toward Earth, estimates of soil moisture could be mapped over time.

“What we’re trying to do is understand the limits of how far can we push that kind of quantitative knowledge using these remote sensing techniques and what new techniques we might need to develop,” he said.

From Brown, where he earned his Ph.D. in 2006, Milliken went to JPL and Caltech. Then in 2010 he took his first professorial position at Notre Dame University. For the former Indiana University undergrad, it was something of a homecoming.

Now he’s back at Brown for a more intimate reunion with people he knows well and can work with over coffee as well as a lab bench.

“I really enjoyed my time here as a graduate student,” he said. “It’s a really collegial group. To be part of that group, where people do a lot of collaborative work together, that was very attractive.”

He’s also looking forward to teaching undergraduates at a relatively small university, after his own undergraduate years at a huge Big Ten school.

“The freshmen seminars that are offered here and the opportunity to teach in smaller groups that offer more one-on-one interaction with students is very exciting,” Milliken said.

Of course that will have to wait until the spring.

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