A tour of Jupiter's Trojan asteroids
Lucy
Lucy launched in October 2021 on a twelve-year journey to the Jupiter Trojans — two swarms of asteroids that lead and trail Jupiter around the Sun. These primitive bodies are thought to be leftovers from the formation of the outer planets.
Along the way it has already flown past two main-belt asteroids, Dinkinesh and Donaldjohanson.
Key facts
- Agency
- NASA / SwRI
- Launched
- 2021-10-16
- Launch vehicle
- Atlas V 401
- Power
- Two circular solar arrays
- Mission type
- Multiple asteroid flybys
- Named after
- The 'Lucy' hominin fossil
- Status
- Heading for the Trojan asteroids that share Jupiter's orbit
Where it is now
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Trojan asteroids from 2027 to 2033.
Mission objectives
Lucy will fly past several Trojan asteroids of different types, mapping their surfaces, measuring their composition and masses, and looking for moons and rings, to learn how the Solar System's planets formed and migrated.
The spacecraft
Two large circular solar arrays power Lucy far from the Sun. Its instruments include a high-resolution camera (L'LORRI), a colour imager and infrared spectrometer (L'Ralph) and a thermal-infrared spectrometer (L'TES).
Journey so far
At its first flyby in November 2023, Lucy discovered that tiny asteroid Dinkinesh has a moon, Selam, which is itself a contact binary. In April 2025 it flew past Donaldjohanson, named after the paleoanthropologist who discovered the Lucy fossil.
Route and timeline
- 2021-10-16Launch, Cape Canaveral
- 2022-10-16Earth gravity assist
- 2023-11-01Dinkinesh flyby
- 2024-12-12Second Earth gravity assist
- 2025-04-20Donaldjohanson flyby
- 2027-08Trojans Eurybates and Quetaplanned
- 2033-03Patroclus–Menoetius binaryplanned
Surprising facts about Lucy
- Lucy will visit more asteroids than any previous mission.
- The Trojans orbit at Jupiter's distance but never come near the planet.
- The mission's name honours the 3.2-million-year-old fossil that transformed our understanding of human evolution.