NASA’s Lucy spacecraft is on a long-haul, first-of-its-kind voyage to unlock the secret history of our solar system, but it’s also filling in more details about more ordinary space rocks along the way.Launched with minimal fanfare in the autumn of 2021, as the COVID pandemic dominated world news, the mission has been quietly plying interplanetary space ever since on a six-year trip to the vicinity of Jupiter. In August 2027 it will arrive at the first of its half-dozen primary targets— “Trojan” asteroids, which swarm by the millions around Jupiter in two great clouds, one ahead of the planet and the other trailing behind.The Trojans are thought to be “fossils” from the solar system’s rough-and-tumble early days, ancient relics pushed into their current locales by violent gravitational interactions between the giant planets. Earth-impacting shrapnel from those primordial upheavals may have helped seed our planet with the precursors for life, delivering water and organic compounds from the dark, icy depths of the outer solar system.If you’re enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.On it way to the Trojans, the spacecraft has tested its instruments in opportunistic studies of main-belt asteroids, which lie between Mars and Jupiter. Lucy flew by one called Dinkinesh in 2023 and then another called Donaldjohanson in 2025. (The latter object is a slowly tumbling, peanut-shaped space rock that is about twice as long as Central Park. Its name honors paleoanthropologist Donald Johanson, who discovered the “Lucy” hominin fossils that transformed our understanding of human origins and inspired the mission’s moniker.)And now, in a study published today in Science, the Lucy team is reporting what it learned from that second asteroid flyby.The results aren’t necessarily surprising, but they demonstrate how much information Lucy can gain even from a brief encounter, previewing some of the spectacular science that the probe will perform in the Trojan clouds, which no spacecraft has ever visited before.Donaldjohanson wasn’t just “a target of opportunity” to assess Lucy’s instruments, says Simone Marchi, an astrophysicist at the Southwest Research Institute, the Lucy mission’s deputy principal investigator and lead author of the new study. That’s because scientists already had a good idea of the asteroid’s provenance: it is a likely member of the Erigone family, a group of asteroids thought to be fragments of a larger body that shattered from a great impact about 150 million years ago.“In terms of the solar system’s history, that’s practically yesterday,” Marchi says, which makes Donaldjohanson a relatively fresh “anchor point” for understanding the subtle ways that asteroids change over time.“On billion-year timescales, it
NASA’s Lucy mission reveals an asteroid’s hidden history
