NASA's Lucy mission nears Jupiter's Trojan asteroids after five years of discoveries

Spacecraft has already revealed surprises at main-belt asteroids and observed a comet impact

By LineZotpaper

Published22 October 2026

Read Time3 min

NASA's Lucy spacecraft, launched in October 2021, is less than a year from its first encounter with the Trojan asteroids near Jupiter, having already made several notable discoveries during its journey, including a contact-binary moon and a peanut-shaped asteroid in the main belt.

NASA's Lucy mission is closing in on its primary target: the Trojan asteroids, two swarms of space rocks that travel ahead of and behind Jupiter in its orbit. No spacecraft has ever explored these asteroids before. Lucy, now five years into its 12-year mission, is scheduled to make its first Trojan flyby in August 2027, researchers from the Southwest Research Institute (SwRI) said on October 19, 2026.

Though it has not yet reached the Trojans, Lucy has already produced a series of discoveries. During a flyby of the main-belt asteroid Dinkinesh in November 2023, the spacecraft found that the asteroid had a tiny moon, later named Selam. Selam itself turned out to be a contact binary, two smaller bodies stuck together, meaning the mission effectively visited three bodies at once.

In April 2025, Lucy flew past another main-belt asteroid, Donaldjohanson. That asteroid is itself a contact binary, peanut-shaped with two large lobes joined by a remarkably smooth neck, according to Simone Marchi, deputy principal investigator for Lucy. Marchi said 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.

Lucy used two Earth gravity assists to gain speed and adjust its trajectory: one in October 2022, passing just 220 miles (350 km) above Earth's surface, and another in December 2024 that increased its speed relative to the sun by over 16,000 mph (25,750 km/h). A third Earth flyby is planned for December 2030.

The mission overcame an early setback when one of its two large solar panels failed to deploy fully after launch. Engineers diagnosed the problem and managed to deploy the panel enough to save the mission.

Lucy also observed other events during its journey, including the DART impact on the near-Earth asteroid Didymos in September 2022 and the interstellar comet 3I/ATLAS in September 2025.

Hal Levison, principal investigator at SwRI, noted that most of the mission still lies ahead. The spacecraft is slated to visit four Trojan asteroid systems: Eurybates and its satellite Queta in August 2027, Polymele and its unnamed satellite in September 2027, Leucus in April 2028, and Orus in November 2028. A second Trojan swarm encounter is expected in March 2033.

"These relics are effectively fossils of the planet formation process, holding vital clues to deciphering the history of our solar system," Levison said.

Analysis

Why This Matters

The Trojan asteroids have never been explored up close, and studying them could reveal key insights into the formation of the solar system.
Lucy's discoveries at main-belt asteroids, including contact binaries and a moon with a moon, highlight the diversity of small bodies in the solar system.
The mission's success after a solar panel issue demonstrates the resilience of NASA's robotic exploration program.

Background

NASA's Lucy mission is the first to target the Jupiter Trojan asteroids, which orbit the Sun in two swarms: one ahead of Jupiter (the Greek camp) and one behind (the Trojan camp). These asteroids are thought to be remnants from the early solar system, preserved for billions of years. Lucy launched in October 2021 and uses a complex trajectory with Earth gravity assists to reach its targets. Before reaching the Trojans, it has already flown by three main-belt asteroids, each providing unexpected scientific results.

Key Perspectives

NASA/SwRI science team: The spacecraft's performance has exceeded expectations, with early flybys providing valuable data and engineering tests. The encontering of contact binaries and a double moon were surprises that underscore the richness of the small-body populatin.

Planetary science community: The Trojan asteroids are a pristin area of research; any data from Lucy will be highly anticiated. The mission is on schedule and within its 12-year timeline.

Space enthusiasts and public: Lucy's progress and discoveries provide a compelling narative of exploration, with the promise of more dramatic findings as it reaches the Trojans.

What to Watch

The first Trojan flyby of Eurybates and its satllite Queta in August 2027.
The behaviour of the solar array and spacecraft health as it enters the Trojan region.
Any addional discoveries during the final appraoch to the Trojan groups.

Sources

Lucy mission to Trojan asteroids: 5 years of discoveries · EarthSky

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12 claims in this story checked against 1 source: 12 supported.

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SupportedLucy is nearing the Trojan asteroids after about five years of discoveries.EarthSky: “Lucy is now less than a year away from meeting its first Trojan. ... Launched on October 16, 2021, Lucy has been traveling for about five years now. But even though it hasn’t reached the asteroids yet, it has already made several remarkable discoveries”
SupportedLucy has revealed surprises at main-belt asteroids and observed a comet impact.EarthSky: “These include new findings at other asteroids in the main asteroid belt between Mars and Jupiter.”
SupportedLucy launched in October 2021 and is less than a year from its first Trojan encounter, scheduled for August 2027.EarthSky: “Launched on October 16, 2021, Lucy has been traveling for about five years now.”
SupportedNo spacecraft has explored the Trojan asteroids before Lucy.EarthSky: “Lucy will be the first mission to explore the Trojan asteroids.”
SupportedDuring its November 2023 Dinkinesh flyby, Lucy found a moon named Selam that is a contact binary.EarthSky: “The asteroid had a tiny moon! ... The little moon, now named Selam, was a contact binary. That is, it had two parts that were joined together.”
SupportedDonaldjohanson is a peanut-shaped contact binary with two large lobes joined by a smooth neck.EarthSky: “Donaldjohanson is peanut-shaped, with two large lobes joined together by a smooth “neck.””
SupportedDonaldjohanson rotates end-over-end once every 10.5 Earth days and rolls around its lateral axis once every 26.5 days.EarthSky: “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.”
SupportedLucy’s December 2024 Earth flyby increased its speed relative to the Sun by over 16,000 mph (25,750 km/h).EarthSky: “Later, in December 2024, the second flyby increased its speed relative to the sun by over 16,000 mph (25,750 km/h).”
SupportedLucy’s third Earth flyby is planned for December 2030.EarthSky: “Lucy will make yet another Earth flyby in December 2030.”
SupportedLucy observed the DART impact on Didymos in September 2022 and the interstellar comet 3I/ATLAS in September 2025.EarthSky: “In September 2022, NASA DART probe impacted the near-Earth asteroid Didymos (on purpose, to demonstrate planetary defense technology). And Lucy saw it happen. In September 2025, Lucy observed the now-famous interstellar comet 3I/ATLAS”
SupportedLucy is slated to visit Eurybates, Polymele, Leucus and Orus in 2027 and 2028, with a second Trojan-swarm encounter in March 2033.EarthSky: “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.”
SupportedLevison said, “These relics are effectively fossils of the planet formation process, holding vital clues to deciphering the history of our solar system.”EarthSky: “These relics are effectively fossils of the planet formation process, holding vital clues to deciphering the history of our solar system.”