On Sept. 26, 2022, NASA conducted the world’s first experiment in planetary defence when it deliberately launched the DART rocket, or Double Asteroid Redirection Test, head-on into the space rock Dimorphos, forever changing its course.
The test was a success, and a slew of recently released analyses in Nature show that scientists are optimistic about the future of the planet-saving technology. While Dimorphos posed no risk to Earth, a day may come when another space rock will.
“I cheered when DART slammed head on into the asteroid for the world’s first planetary defence technology demonstration, and that was just the start,” said Nicola Fox, associate administrator for the Science Mission Directorate at NASA Headquarters in Washington. “These findings add to our fundamental understanding of asteroids and build a foundation for how humanity can defend Earth from a potentially hazardous asteroid by altering its course.”
The mission, which cost US$330 million, saw NASA launch a SpaceX Falcon 9 rocket directly into the asteroid moonlet Dimorphos at 24,139 kilometres per hour. Dimorphos measures about 160 metres across and orbits the asteroid Didymos.
Scientists conservatively predicted that the rocket impact would shorten the period of time it takes for Dimorphos to orbit Didymos by seven minutes. However, a study published in Nature on Wednesday reports that the test shortened Dimorphos’ orbit by a full 33 minutes.
The investigation team, led by Cristina Thomas of Northern Arizona University, found that DART had a larger effect on the moonlet because of the material that ejected off its surface after the rocket impact. The “ejecta,” as it’s known, “contributed significant momentum change” to Dimorphos, “beyond that of the DART spacecraft itself.”
In sum, the authors concluded: “To serve as a proof-of-concept for the kinetic impactor technique of planetary defense, DART needed to demonstrate that an asteroid could be targeted during a high-speed encounter and that the target’s orbit could be changed. DART has successfully done both.”
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In fact, by creating this ejecta trail, DART’s impact has turned Dimorphos from an asteroid moonlet into an “active asteroid,” another Nature study found.
The paper, led by Jian-Yang Li of the Planetary Science Institute, observed that Dimorphos still orbits like an asteroid but now has a tail of material like a comet.
“Although scientists had proposed that some active asteroids are the result of impact events, until now no one had ever observed the activation of an asteroid,” a press release from NASA reads.
Another Nature study evaluated that DART was successful at autonomously targeting Dimorphos “with limited prior observations,” which has scientists hopeful that the technology can actually be used in real-life scenarios to defend Earth.
However, NASA wrote in its press release that scientists would still need advance warning of at least several years, though preferably decades, to gather the information necessary to target an asteroid.
“Nevertheless,” the authors of the paper state, DART’s success “builds optimism about humanity’s capacity to protect the Earth from an asteroid threat.”
“We are so proud of the DART team and the investigation’s latest results,” said Jason Kalirai at Johns Hopkins Applied Physics Laboratory, which led the overall investigation. “With the core analysis activities starting after the impact of Dimorphos, the results demonstrate how successful the kinetic impactor technique can be — paving the way for a bright future for planetary defence.”
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