NASA's asteroid-studying spacecraft Lucy captured an image of its next flyby target, the asteroid Donaldjohanson. On April 20th, the spacecraft will pass within 960 km of the small, main belt asteroid. It will keep imaging it for the next two months as part of its optical navigation program.
Understanding Asteroid Donaldjohanson
Donaldjohanson is an unwieldy name for an asteroid, but it’s fitting. Donald Johanson is an American paleoanthropologist who uncovered an important australopithecine skeleton in Ethiopia’s Afar Triangle in 1974. The female hominin skeleton showed that bipedal walking developed before larger brain sizes, an important milestone in human evolution. She was named Lucy.
NASA named their asteroid-studying mission Lucy to uncover clues about our origins. Instead of ancient skeletal remains, Lucy will study asteroids, which are akin to fossils of planet formation.
Mission Overview
During its 12-year mission, Lucy will visit eight asteroids. Two are in the main belt, and six are Jupiter trojans. Asteroid Donaldjohanson is a main-belt, carbonaceous C-type asteroid—the most common variety—about 4 km in diameter and is Lucy's first target. It’s not one of the mission’s primary scientific targets. Instead, the flyby will allow Lucy mission personnel an opportunity to test and calibrate the spacecraft’s navigation system and instruments.
Preliminary Results
The animation below shows images captured by Lucy on Feb. 20th and 22nd. It depicts the perceived motion of Donaldjohanson relative to the background stars as the spacecraft rapidly approaches the asteroid.
The flyby serves as a practice run before Lucy visits the Jupiter trojans. These asteroids consist of clusters of rock and ice that never coalesced into planets during Solar System formation. These trojans represent the "fossils of planet formation," the most well-preserved evidence from the days of Solar System formation.
Currently, Donaldjohanson is 70 million km away and will remain a tiny point of light for weeks. Only on the day of the encounter will the spacecraft’s cameras capture any detail on the asteroid’s surface. In the images above, the dim asteroid still stands out from the dimmer stars of the constellation Sextans. Lucy’s high-resolution L’LORRI instrument, the Long Lucy LOng Range Reconnaissance Imager, captured the images.
Trajectory Details
Lucy is following a unique flight pattern. It’s essentially a long figure-eight.
Discoveries from Dinkinesh Flyby
Even early on in its mission, Lucy has delivered surprising results. In November 2023, it flew past asteroid 152830 Dinkinesh. The flyby was intended as a test for the spacecraft’s braking system, but instead revealed that Dinkinesh possesses a small satellite. Further observations indicated that this satellite is a contact binary, comprised of two connected bodies. This finding contributes valuable insights into asteroids.
Future Considerations
There are always unexpected discoveries in any mission, and Lucy is no exception. As it progresses through its list of targets, it will likely unveil even more surprises.
The Trojans are challenging to scrutinize from a distance, being situated a considerable distance away. Scientists are unsure of their population; there may be as many Trojans as there are main-belt asteroids. The Trojans showcase a diversity of compositions and characteristics, suggesting that they originated from different regions of the Solar System. By investigating the Trojans and their diversity, Lucy hopes to help scientists reconstruct their origins and the circumstances under which they were captured by Jupiter.
Conclusion: Unraveling Solar System History
The Solar System boasts an extensive history, and humanity has only begun to fathom its vastness. Some clues to our origins lie among the battered rocks of the asteroid belt and the Jupiter Trojans. Lucy will afford us our best look yet at the Trojans. The mission holds the promise of unprecedented discoveries that could reshape our understanding of planetary origins.
For More Information
- Press Release: NASA's Lucy Spacecraft Takes Its 1st Images of Asteroid Donaldjohanson
- Press Release: NASA Lucy Images Reveal Asteroid Dinkinesh to be Surprisingly Complex
- ASU Institute of Human Origins: Lucy’s Story
By continuing to explore these remnants from our Solar System's past, we can gain profound insights into the origins of planets, asteroids, and, ultimately, ourselves.
