NASA launches robotic archaeologist Lucy on an ambitious mission to Trojan asteroids

Lucy will visit 8 asteroids over the next 12 years.

Artist’s depictions of the eight asteroids that NASA’s Lucy mission will visit. (Image credit: NASA Goddard/YouTube)

CAPE CANAVERAL, Fla. — NASA’s newest asteroid probe, named Lucy, blasted off from Kennedy Space Center here in Florida to embark on a 12-year mission to study two different clusters of asteroids around Jupiter known as Trojans. 

These swarms represent the final unexplored regions of asteroids in the solar system. Lucy, acting as a robotic archaeologist, will help to answer questions about how the giant planets formed. 

Perched atop a United Launch Alliance (ULA) Atlas V rocket, the refrigerator-sized spacecraft lit up the predawn skies above Cape Canaveral as it leapt off its launch pad right on time at 5:34 a.m. EDT (0934 GMT) Saturday morning (Oct. 16). Just under two hours after launch, NASA confirmed Lucy’s solar arrays had deployed and it had successfully phoned home.

Lucy will spend the next six years cruising through the solar system, looping around the Earth twice in order to build up enough momentum to reach Jupiter. The spacecraft will fly by a total of eight different asteroids (seven Trojans, which are located in two separate swarms, ahead of and behind the massive planet in its orbit, and one main belt) in order to help scientists better understand how the solar system evolved. Researchers believe that the Trojans are perfectly preserved cosmic time capsules and hope that studying them could shed more light on the origin of the solar system and how the giant planets formed. 

“The reason why [the Trojans] are important scientifically is that they were essentially leftovers,” Hal Levison, Lucy’s principal investigator at the Southwest Research Institute, told

Believed to be fragments of the early solar system, the Trojans are gravitationally locked in stable orbits at the same distance from the sun as Jupiter. With the help of a suite of scientific instruments, Lucy will study the geology, composition, density and structure of each of its Trojan targets.

To date, space agencies around the world have explored a variety of small bodies from the asteroid belt to near-Earth asteroids (using projects like Japan’s Hayabusa mission and NASA’s OSIRIS-REx) to the icy expanse of the Kuiper belt. 

But one area remains unexplored: the Trojan swarms around Jupiter. Approximately 10,000 objects have been discovered in these two regions ranging from a few kilometers across to hundreds of kilometers in diameter. First spotted more than a century ago, astronomers at the time were naming the objects after heroes in Homer’s Iliad, earning the region’s inhabitants the name “Trojans.” 

The mission is named “Lucy” as a nod to the 3.2 million-year-old hominin skeleton discovered in 1974 by a paleoanthropologist named Donald Johanson. At the time, the skeleton was the oldest and most complete hominin discovered and it revealed some secrets of human evolution. NASA named its newest spacecraft Lucy because it hopes that the robotic probe can help unlock some secrets of solar system evolution.

“I will never look at Jupiter the same,” Johanson said after watching the Lucy mission launch from Florida.  “To be out here this morning was absolutely mind-expanding, and it was such a positive experience.”

Early theories as to how the solar system formed envisioned a star in the center of a rotating disk of protoplanetary material. Gradually, the material would condense and collect in clumps to form the planets. Advertisement

But when planetary scientist Hal Levison tried to simulate this, he kept running into a problem: the orbits of Uranus and Neptune did not match up. It was impossible to build these two giant planets in their current orbits. So, Levison tweaked his simulation and developed a new model called the Nice model of solar system evolution, which suggests that the giant planets formed much closer to the sun.

Thanks to the increasingly eccentric orbits of young Jupiter and Saturn, the solar system was rearranged and Neptune and Uranus were kicked out of place and flung into the outer solar system. As they migrated outward, they scattered the small bodies of the solar system. Comets and asteroids were flung to the deep outer solar system, and some were even ejected out of the solar system and into the Milky Way.

As this was happening, a small set of the scattered asteroids were trapped by Jupiter’s gravitational tractor beam and locked in an orbital dance at two of Jupiter’s permanent Lagrange points, which are regions of space where the gravitational and orbital influences of the planet and the sun are balanced.