Five years after its launch, NASA's Lucy probe has reached a cluster of Jupiter's Trojan asteroids. The spacecraft travelled more than three and a half billion kilometres and entered the region near one of the Lagrange points, where the gravitational pull of the Sun and Jupiter balances, allowing small celestial bodies to hold a stable position. Here, thousands of asteroids move ahead of Jupiter in its orbit.
The Trojan asteroids are considered a kind of "time capsule" more than four billion years old. Scientists hope that studying them will help explain what material the outer planets were built from and how the Solar System acquired its present appearance. Current models suggest that these asteroids may have formed in different parts of the system and were then moved by the gravity of the giant planets into their present orbits. Lucy is set to test this hypothesis.
Although the probe has entered the cluster's region, less than a year remains before its first close encounter. The average distance between neighbouring asteroids here exceeds nine million kilometres, and for now the cameras see the targets only as points against the background of stars. On 11 August 2027, Lucy will pass close to the asteroid Eurybates and its moon Queta. Eurybates is of particular interest to researchers as the largest surviving fragment of an ancient collision.
After that, the spacecraft will meet three more asteroids, and in 2030 it will return to Earth for a gravity assist. It will direct the probe toward the second cluster of Trojans, which trails Jupiter. There, a flyby of the binary system Patroclus and Menoetius is scheduled for 2033. Over the course of its 12-year mission, Lucy is to explore eight Trojan asteroids and three objects from the main asteroid belt.
On its way to Jupiter, the spacecraft has already made several discoveries. In November 2023 it flew past the asteroid Dinkinesh and discovered a moon around it, Selam. Later it became clear that Selam itself consists of two touching bodies — scientists saw such a system, orbiting another asteroid, for the first time. NASA reports that all of the probe's systems and scientific instruments are operating normally.
Letters