The Lucy spacecraft has taken the first images of its next target, the small asteroid Donaldjohnanson. It will rendezvous with the asteroid in April 2025.
The Lucy mission was launched in October 2021. Its goal is to study Trojan asteroids in Jupiterian orbit. This is how astronomers designate two large groups of objects that are constantly in the neighborhood of the L₄ and L₅ Lagrangian points of the Sun-Jupiter system. There is speculation that many of them are actually Kuiper Belt objects. Many of them moved into their current orbit during the migration of gas giants that occurred several hundred million years after the Sun was born and the formation of planets was completed. If this theory is correct, studying Trojan asteroids would give us a literal glimpse into the outskirts of the Solar System without the need to fly there.
On its way to the Lagrange points, Lucy will pass through the Main Asteroid Belt several times, giving scientists the opportunity to study the passing asteroids. In 2023, the vehicle already made a flyby of such an object — the asteroid Dinkinesh. It turns out it has a companion called Selam.
Lucy’s next target will be the four-kilometer asteroid Donaldjohanson. On April 20, it will fly at a distance of 960 kilometers from the asteroid. This visit will be a dress rehearsal before the main part of Lucy’s science program begins.
Mission specialists are already preparing for the flyby. In February, Lucy photographed the asteroid for the first time as part of its optical navigation program. It uses the apparent position of an object against a background of stars to determine its exact position and calculate its trajectory.
In the published images, taken on February 20 and 22, Donaldjohanson appeared as a small dot moving relative to the background stars of the constellation Sextans. At the time of imaging, Lucy was at a distance of 70 million kilometers from its target. A background asteroid was also included in the first image.
Asteroid Donaldjohanson is named after anthropologist Donald Johanson, who discovered the famous skeleton of a female Australopithecus, which was given the name Lucy.
Mission Lucy was named in honor of this fossil. We don’t know much about the asteroid at this point. Based on its light curve, it is thought to either have an elongated shape or is actually a double object. The answer to that question we will know very soon.
