On Oct. 16, 2021, NASA’s Lucy spacecraft began its journey to the never-before-explored Jupiter Trojan asteroids with an early morning launch. Now less than a year away from the first-ever close-up of a Trojan, the Southwest Research Institute–led mission has already made several findings during its first five years.
“Lucy is an ambitious NASA mission, with plans to visit 11 asteroids in its 12-year mission to tour the Trojan asteroids that are located in two swarms leading and trailing Jupiter,” said Dr. Hal Levison, principal investigator of the mission.
“As we passed through the main asteroid belt, we visited three asteroids, capturing close-up views of those bodies while performing engineering tests of the spacecraft’s innovative navigation system in advance of the main event to study the Trojans. These relics are effectively fossils of the planet formation process, holding vital clues to deciphering the history of our solar system.”
In 2022, when the team discovered that Lucy’s planned trajectory would take it near a tiny, then-unnamed main-belt asteroid, they worked quickly to add an encounter with this small object as an additional test for the spacecraft’s systems.
Not only did the spacecraft meet all expectations, but the November 2023 flyby discovered that the asteroid, now named Dinkinesh, had a satellite, so it counted as two asteroids. And then the team was shocked to observe that the moonlet, now named Selam, is a contact binary—a single object made of two touching parts.
“Though contact binaries seem to be fairly common in the solar system, we haven’t had the opportunity to see many up close,” said SwRI’s John Spencer, Lucy deputy project scientist. “And we have never seen one orbiting another asteroid.”
In April 2025, Lucy flew by the main-belt asteroid Donaldjohanson, discovering that it’s also a contact binary, with spin and surface features that had been modified by the sun’s radiation.
“The Donaldjohanson flyby revealed many surprises about the small asteroid. For instance, the peanut-shaped, two-lobed structure is connected by a remarkably smooth neck,” said SwRI’s Dr. Simone Marchi, the mission’s deputy principal investigator. “The asteroid also wobbles, rotating end-over-end once every 10.5 Earth days while rolling around its lateral axis once every 26.5 days.”
The successes of the Lucy mission so far also include feats of engineering. Shortly after launch, the team had to fix one of Lucy’s two giant solar arrays, which had failed to fully deploy after launch. From millions of miles away, engineers diagnosed the problem and devised procedures to get the array almost fully open. The stabilized array now functions as intended.
Lucy has passed by Earth twice since launch, to boost its speed through maneuvers known as gravity assists. In October 2022, Lucy passed 220 miles (354 kilometers) above the surface of the Earth, an encounter that propelled Lucy into a two-year solar orbit.
In December 2024, the second flyby increased its speed relative to the sun by over 16,000 mph (26,000 kilometers per hour), putting it on a current path to make its first Trojan encounter in August 2027. During the first assist, Lucy took images of Earth and the moon to calibrate the spacecraft’s instruments.
Lucy has also provided a unique perspective on a couple of rare events. In September 2022, Lucy observed Dimorphos, a tiny satellite orbiting the near-Earth asteroid Didymos, as it was impacted by NASA’s DART spacecraft to demonstrate a potential planetary defense technology.
Then, in September 2025, Lucy observed the interstellar comet 3I/ATLAS as it passed through our solar system. By viewing these events from different angles than available from Earth, Lucy provided unique observations of these two rare events.
“Despite these eventful five years, most of Lucy’s mission still lies ahead,” Levison said. “The main events start in less than a year as Lucy gets a close-up look at four Trojan asteroid systems: Eurybates and its satellite Queta in August 2027, Polymele and its as-yet-unnamed satellite in September 2027, Leucus in April 2028 and Orus in November 2028.”
Lucy will then loop back into the inner solar system for another Earth gravity assist in December 2030. This boost will slingshot the spacecraft to the other Trojan swarm to visit the binary asteroid pair Patroclus and Menoetius in March 2033.
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Southwest Research Institute
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Lucy mission marks 5 years of discoveries (2026, October 20)
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