Here are the eight asteroids that NASA's Lucy probe will visit
The Trojans are not quite like the rocks found in the asteroid belt . They are all remnants of the formation of the solar system. But while rocks in the asteroid belt have a wide reflectivity range, or albedo, Trojans tend to be mostly non-reflective rocks. The Trojans also differ in that they orbit farther from the Sun, close to Jupiter's orbit.
The mission will be powered by solar panels and is equipped with four instruments capable of observing temperature, albedo and surface characteristics of the asteroids it will visit. Lucy plans to visit eight asteroids: a main belt rock and seven Trojans.
Donaldjohanson
The first is Donaldjohanson, the smallest of Lucy's targets and the only non-Trojan . This inhabitant of the 4 km wide asteroid belt is actually a test for the mission's tools. Astronomers speculate that this dim and tiny object may be a fragment of an ancient collision that produced a family of asteroids, the largest of which is called Erigone. Known as a C-type asteroid, meaning it is likely rich in carbon, Donaldjohanson has rock-like properties that NASA's OSIRIS-REx and Japan's Hayabusa2 asteroid sampling missions have studied. Lucy is expected to fly around this asteroid on April 20, 2025.Eurybates and Queta
Eurybates and her little companion Queta will be Lucy's next targets. These are the first Trojan rocks Lucy will visit, with a flyby scheduled for August 12, 2027. Eurybates is significantly larger than Donaldjohanson; the great Trojan is approximately 64 km in diameter and will serve as a good starting point for mission specialists who want a solid introduction to the Trojans. Astronomers think the asteroid is the largest remaining chunk of a massive collision. Furthermore, this C-type asteroid is a bit strange among the Trojans because C-type asteroids are usually found in the main asteroid belt. Its presence in the cluster is another mystery that scientists hope to answer with Lucy.Queta is instead the little companion of Eurybates, a natural satellite measuring just one kilometer, detected in 2019 by the Hubble Space Telescope . There are only a handful of known cases in which Trojan asteroids have a companion.
credits: NASA Goddard / YouTube
Polymele
Lucy's third stage will take place about a month later, on asteroid Polymele. This will be the first time Lucy has encountered a P-type asteroid, a class known to be reddish in color and thought to be composed of organic elements. Polymele is 21 km in diameter, Lucy will visit it on September 15, 2027. Lucy will encounter another series of P-type asteroids later in her mission, but the others will be much larger, which will offer scientists an intriguing confrontation.Leucus
The next target is called Leucus, an asteroid 40 km wide. It is a D-type asteroid, a variety that is also thought to be composed of organic elements. Leucus rotates very slowly, taking about 446 hours to make one revolution. Lucy will determine if this slow rotation makes the day side of the asteroid significantly warmer than its night side. Scientists think that Leucus is elongated because its brightness also varies a lot. Lucy will visit Leucus on April 18, 2028.Orus
A little over half a year later, Lucy will visit Orus. This is also a type D rock, with a deep red color. Orus has a diameter of 51 km and is about the size of Eurybates. The comparison of these two objects, similar except for their colors, serves as the backbone of the Lucy mission.Orus is the last of the L4 swarm that Lucy will visit. The "L" in this category refers to the Lagrange point, which are places throughout the solar system where gravity is stable. Lagrange points near Jupiter have held the Trojans in place for billions of years. Lucy will study two Trojan asteroid swarms that have gathered at distinct Lagrange points, the L4 point in front of Jupiter and the L5 point behind it.
Once Lucy leaves Orus after her 11th visit November 2028, the spacecraft will leave the L4 swarm and plunge back into the inner solar system to conduct a flyby of the Earth.
Patroclus and Menoezio
Five years after flying over Orus, Lucy will overtake two asteroids in the L5 swarm, following Jupiter in its orbit around the Sun. Patroclus and Menoethius make up a fairly uniform binary pair of asteroids, which is a rare phenomenon in the inner solar system. These organically rich P-type Trojans are large: Patroclus is 113 km wide and Menoethius is slightly smaller, 104 km in diameter.Lucy mission specialists are looking forward to this meeting because they hope the duo is an almost untouched example of what the planets formed from. This flyby will take place on March 3, 2033.
