Written by: El Hebert '24
Edited by: Ashley Nee '22
Ralph Milliken, Ph.D., is one of many Brown community members involved with NASA - his work pinpointed a landing site for the Curiosity rover. Now, new discoveries continue to unfold as our university collaborates with space programs on an international - and interplanetary - scale.
A returned Brown alumnus, Milliken works in the Department of Earth, Environmental and Planetary Sciences (EEPS). His field, he says, is a “pretty widespread” one: it covers both diverse research and vast distances.
For example, in 2018, the Hayabusa2 spacecraft punched the asteroid Ryugu with an impactor, sampling the debris. Last December, it finally delivered its capsule back to our own planet and into the eager hands of scientists. NASA’s Osiris-Rex, en route from asteroid Bennu, will do the same in 2023. That extraterrestrial material may not look like much - a few grams of black, grainy sand - but Milliken’s team and their Japanese colleagues hope to compare the samples for a glimpse into the early formation of the solar system .
With the mind-boggling size of space, though, sample-return missions are the exception rather than the rule. So Milliken also uses remote sensing technology, and works on the Curiosity rover mission, performing vicarious experiments on Mars.
When Milliken got involved with the Curiosity project as a researcher at the Jet Propulsion Laboratory, the rover hadn’t even launched yet. His first contribution, in fact, was a suggested landing site. NASA accepts such proposals as an “open competition,” placing them under scrutiny in a gauntlet of publicly-held meetings.
“I became very interested in advocating for this place called Gale Crater,” Milliken recalls. “We thought it was extremely scientifically compelling.” What does it take to advocate for a geological feature on another planet? Data, data, and more data. Milliken and his colleagues analyzed the topography closely enough to map the individual boulders. After all, any one of them might have posed a hazard to the robot as it touched down.
Ultimately, Milliken’s work paid off, and the team chose Gale Crater as the landing site - it was “both exciting and a little bit nerve wracking.”
In August 2012, Curiosity’s lander successfully lowered the rover down onto the surface of Mars. Since then, Curiosity has logged a distinguished career of 3,000 Martian days, with 25 kilometers traveled - not bad at all, for a vehicle that moves at one centimeter per second . Milliken is still on the rover team, and still excited about Curiosity’s contributions to science: not only is the team gaining essential understanding of a geology that may have once supported life, they’re also “chipping away at the really core important things for sending humans.” Thanks to Curiosity’s measurements, we can better anticipate radiation at the planet’s surface, and design effective protection against it.
Curiosity’s sibling, Perseverance, landed without a hitch in February. It’ll continue to search for ancient signs of life, and test new technologies, like powered flight in the Martian atmosphere, and oxygen generation that may someday provide fuel and breathable air.
Among the thousands of people involved with the Perseverance mission are some of Milliken’s former students.
Brown’s planetary sciences department collaborates extensively with NASA. The space program funds research, both on Earth and elsewhere, and professors and fellows work directly on mission teams. Historically, Professor Thomas Andrew “Tim” Mutch helped design the first cameras ever to land on Mars; Professor James Head trained Apollo astronauts in geology.
Milliken also emphasizes the importance of international partnerships, like the Hayabusa2 sample analysis effort, or Professor Carle Pieters’ involvement with the Moon Mineralogy Mapper launched by India. Together, the global space exploration community can pool the funds, technology, and diverse perspectives required for effective exploration in the deep solar system.
“It's definitely been eye opening for me, seeing how [international collaboration] helps the science,” Milliken says. “There aren't any borders out there. Those are constructs that we made here on Earth. I think, to be successful, it absolutely has to be focused more on humankind as a whole, as opposed to just one nation or another - building those partnerships and relying on those strengths.”
Meanwhile, the field of planetary science has its sights set on a few “amazingly crazy fascinating” worlds. One is Psyche, the naked metallic core of a shattered planetary body. Another mission, Lucy, is set to visit the Trojan asteroids, and may reveal the ancient paths of migrating gas giants. There’s also Dragonfly, a rotocopter bound for Saturn’s moon Titan, where hydrocarbon rivers run under an orange sky. And of four potential “discovery-class” missions currently under review by NASA, three of them have Brown graduates as lead developers.
Literally and figuratively, it seems, the universe is only getting bigger.
Milliken R. Interviewed by: Elise Hebert. March 9, 2021 [Cited March 21, 2021].
 Strickland A. Hayabusa2 mission confirms return of an asteroid sample, including gas, to Earth. CNN [Internet]. 2020 [Cited March 21, 2021]. Available from: https://www.cnn.com/2020/12/15/world/hayabusa2-asteroid-gas-sample-scn-trnd/index.html.
 NASA Mars Exploration Program. Rover Wheels [Internet]. [Cited March 21, 2021]. Available from: https://mars.nasa.gov/mer/mission/rover/wheels-and-legs.