The International Astronomical Union has officially assigned names to the surface features of asteroid 52246 Donaldjohanson, a celestial body observed by NASA’s Lucy spacecraft during a close flyby on April 20, 2025. The new labels, rooted in the history of human origins, provide the first detailed map of the asteroid and solidify the legacy of the spacecraft’s encounter while it journeys toward its primary targets in the outer solar system.
The naming convention creates a direct link between the exploration of the solar system’s past and the study of humanity’s own origins. Donaldjohanson, located in the main asteroid belt between Mars and Jupiter, served as a crucial test for the Lucy mission’s instruments and navigation. The approval of names for its craters, lobes, and other geological features allows scientists to more easily discuss and analyze the data returned from the spacecraft, which revealed the asteroid to have a distinct peanut-like shape.
A Celestial Map of Human Origins
In a tribute to the mission’s own namesake—the “Lucy” hominin fossil—the Lucy science team proposed a naming theme centered on paleoanthropology, which the IAU has now formally adopted. The asteroid’s bilobed structure offered unique opportunities for naming major geological regions. The larger of its two main sections is now called Olduvai Lobus, honoring the Tanzanian river gorge that has yielded many critical discoveries of early human ancestors. The smaller portion is named Afar Lobus, for the region in Ethiopia where the famous 3.2-million-year-old Lucy skeleton was discovered in 1974 by paleoanthropologist Donald Johanson, the asteroid’s own namesake.
Connecting these two major lobes is a feature now designated Windover Collum. This marks the first time the IAU has officially recognized and named an asteroid’s “neck” or “collum.” The name honors the Windover Archeological Site, a significant location near Cape Canaveral, Florida, where the Lucy spacecraft began its journey in 2021. Other, smaller features have also been cataloged. Two smooth areas on the neck have been named the Hadar region, after the site of the Lucy fossil’s discovery, and the Minatogawa region, where the oldest known hominins in Japan were found. Additional craters and boulders are named after other notable hominin and human fossils, further cementing the asteroid’s connection to the story of our species.
The Encounter in the Asteroid Belt
The Lucy spacecraft’s flyby of Donaldjohanson was more than just a brief visit; it was a comprehensive dress rehearsal for its primary scientific objectives. On April 20, 2025, the probe passed within approximately 960 kilometers (596 miles) of the asteroid, allowing its three primary science instruments to execute observation sequences nearly identical to those planned for the main mission targets. This engineering test was a success, confirming the spacecraft’s ability to autonomously track a target and gather high-resolution data during a high-speed encounter.
Data from the flyby revealed Donaldjohanson as a carbonaceous asteroid measuring approximately 8 kilometers (5 miles) long and 3.5 kilometers (2.2 miles) wide. Its distinct shape, with two lobes joined by a central neck, suggests a complex history. Scientific models indicate it may have formed around 155 million years ago when a larger parent asteroid was shattered in a collision. The detailed imagery captured by Lucy provides crucial clues about how such “contact binary” objects form and evolve over time.
A Mission Inspired by a Fossil
The thematic naming of Donaldjohanson’s features highlights a chain of inspiration that stretches back decades. The Lucy mission itself is named after the transformative fossil discovered by Donald Johanson. That discovery revolutionized our understanding of human evolution, and NASA’s mission aims to achieve a similar revolution in our understanding of the solar system’s evolution by studying primitive asteroids. These asteroids are considered “fossils of planet formation”—pristine remnants from the dawn of the solar system more than 4 billion years ago.
The asteroid Donaldjohanson was named in 2015 to honor the paleoanthropologist. The flyby marked a unique occasion, as it is the only asteroid to be visited by a spacecraft while its namesake is still living. By proposing to name the asteroid’s features after significant sites and fossils, the mission team has woven together the parallel quests for knowledge about our planetary and human pasts.
Journey to the Trojans
While the mapping of Donaldjohanson is a significant milestone, it is just one step in a much longer voyage. The Lucy spacecraft, which launched on October 16, 2021, is on a 12-year journey to explore a record-breaking number of asteroids. Its primary targets are the Jupiter Trojan asteroids, two large swarms of celestial bodies that share Jupiter’s orbit, one group leading the giant planet and one trailing behind.
These Trojan asteroids are believed to be captured remnants from the outer solar system, holding clues to the materials that formed the giant planets. Having completed its flybys of main-belt asteroids Dinkinesh (in 2023) and Donaldjohanson, Lucy is now en route to its first Trojan target. The spacecraft is scheduled to arrive at the asteroid Eurybates in August 2027, where it will begin the main science phase of its ambitious mission to unlock the secrets of our solar system’s formation.