We’re about 66 million years too late to save the dinosaurs, but the recent successful DART (double asteroid redirection test) mission may one day allow us to save ourselves. It’s not just the ability to change the orbital period of an object in space that makes the project, completed in September, so interesting, said Mallory DeCoster, who worked on the mission, but also that the science collected will help us learn a lot about the composition of the asteroid and what a monumental strike leaves behind, both on the asteroid and released into space. Like any professional scientist who talks about the project, she makes it clear that our planet was never threatened by the small body Dimorphos, in the orbit of Didymos.
DeCoster is a Crozet resident who has been working with NASA and the Johns Hopkins Applied Physics Laboratory on the project. While most of us feel overwhelmed when we consider the knowledge necessary to understand the intersection of chemistry, physics and mechanical engineering, it always came naturally to DeCoster.
Many scientists who find themselves working on the mysteries of the mostly unseen universe are drawn there by a fascination with space, but DeCoster’s route was different. “I was always the one more interested in physics,” she said. “From the time I was in middle school, I found science, including chemistry and engineering, fascinating.” She was a child of the Southwest who came to Virginia by way of an obligation. She completed her master’s degree as a civilian in the Naval Postgraduate school in California, and its support of her degree required her to spend a year as an employee of the Department of Defense. That brought her to Charlottesville, the home of the National Ground Intelligence Center.
“I had never even heard of Charlottesville,” she said, “but I fell in love with the whole area.” She also fell in love with the field of applied physics and, when her year was up, she began working at Johns Hopkins Applied Physics Lab in Laurel, Maryland. They offered her a chance to get a Ph.D. in mechanical engineering at U.Va. while continuing to work part-time for them.
Once her Ph.D. was complete, she was able to continue at the lab and eventually become part of the DART team.
She notes that, though led by NASA, the mission brought her together with scientists from all over the world. “If you’re working on planetary defense, there has to be collaboration,” she said. “Obviously, it’s harder when there are political differences between countries, but if there were to be a really credible threat, we’d have to join forces. We don’t get to choose where in the world an asteroid might be headed.”
DeCoster’s team is charged with examining the scientific findings gathered by the mission. “Obviously the first goal was to actually hit the asteroid,” she said, “to change its orbital period, and to measure that change.” The 32-minute change, as measured by an earth-based telescope, was more than the team had anticipated, although well within the range predicted.
Still, with an asteroid headed straight for us, isn’t that kind of change insignificant— perhaps only prolonging the agonizing anticipation of the event? She explained that this kind of small nudge accumulates over time and distance, sending an asteroid as many as millions of miles away from its previous course.
Time is the essential constraint on everything we do in space. DeCoster said the mission was launched 10 months before its anticipated impact was publicized. NASA keeps its eye on thousands of objects circulating, with more discovered every day, in hopes of discovering a dangerous trajectory years before it actually becomes dangerous.
People are able to relate to this mission more than they can to other important NASA projects, DeCoster said, because just such an event––the world responding to a threatening asteroid—has been pictured in popular science fiction books and films. In fictionalized accounts, the offending asteroid is often blown up by charismatic scientists on the ground or heroes in space suits with the help of a nuclear device. “Obviously, this would have terrible implications for the future,” DeCoster said. “We don’t want nuclear debris floating around in space.” Also, unlike the fictionalized versions, there was no direct control from the ground once the mission was launched. The spacecraft carried an autonomous navigation system.
Her team has an interest in the kind of debris formed by the real-life impact of an object the size of a vending machine hitting an object the size of the Empire State Building, in this case at about 14,000 miles per hour. The debris, called ejecta, factors into the complicated physics involved in the movement of the asteroid––the more ejecta, the larger the thrust. And the debris also tells us what asteroids, or at least this particular asteroid, are made of.
“We didn’t know if this was a kind of basalt rock, or a sandy mass,”DeCoster said. It turns out it’s both: “Our preliminary studies show that there are a lot of large monolithic chunks in a sandy matrix.”
DeCoster’s job title is that of co-investigator of the impact modeling working group. She’s also found herself speaking to the public about the mission, and has had some success in that role. Unlike some scientists, “I’ve learned to take out the jargon,” she said. “I really enjoy bringing our work to a larger audience.”
Find out more on NASA’s website: www.jpl.nasa.gov/edu/news /2022/9/22/the-science-behind-nasas-first-attempt-at-redirecting-an-asteroid/; and hear DeCoster speak about her work on the Brad Rykal Brief, a Crozet-based podcast (story here!), on any podcast platform.
