This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: 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.
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