Lucy Trojan Asteroid Mission
On October 16, 2021, NASA launched Lucy—the first mission to study Jupiter’s Trojan asteroids, two swarms of primitive bodies sharing Jupiter’s orbit at gravitationally stable Lagrange points. The 12-year mission will visit eight asteroids representing time capsules from the solar system’s formation 4.5 billion years ago.
Trojans occupy L4 and L5 Lagrange points—stable regions where Jupiter’s and the Sun’s gravitational forces balance, trapping asteroids in Jupiter’s orbital path. The ~7,000 known Trojans are thought to be remnants from the outer solar system’s formation, potentially kicked inward during planetary migration events that reshaped the early solar system.
Lucy’s trajectory includes one main-belt asteroid flyby (Donaldjohanson, named after the “Lucy” fossil’s discoverer), then visits to five Trojans in Jupiter’s L4 swarm (2027-2028), a return to Earth for gravity assist, and finally two Trojans in the L5 swarm (2033). The mission’s name honors the famous human ancestor fossil—both “Lucy” discoveries shed light on origins.
The spacecraft carries three instruments: L’Ralph (color imaging and composition), L’LORRI (high-resolution imaging), and L’TES (thermal emission), enabling detailed characterization of asteroid sizes, shapes, surface features, compositions, and thermal properties. Scientists expect to find diverse asteroid types reflecting different formation regions.
Launch occurred successfully despite a solar array deployment issue discovered weeks later—one of two circular arrays failed to fully latch, though NASA determined it remained stable enough for the mission. By 2023, Lucy executed its first asteroid encounter (Donaldjohanson in November 2023), beginning its decade-long tour through solar system relics.
https://www.nasa.gov/lucy https://lucy.swri.edu https://www.nature.com/