NASA's Lucy spacecraft has captured stunning images and unveiled intriguing findings from its flyby of the asteroid Dinkinesh, providing insights into the formation of the solar system and the early stages of planet formation.
Launched in 2021, Lucy is a 12-year mission aimed at studying asteroids, particularly Jupiter's Trojan asteroids-two groups of space rocks that lead and trail the giant planet as it orbits the Sun.
On its journey, Lucy made a close flyby of the asteroid Dinkinesh, located on the inner edge of the main asteroid belt between Mars and Jupiter. This flyby occurred in November 2023, providing the first close-up images and data of the small asteroid and its moonlet, Selam.
NASA's Lucy spacecraft captures stunning images of asteroid Dinkinesh, revealing dynamic history and formation insights, including its contact-binary moonlet, Selam.Image via NASA/GSFC/SwRI/Johns Hopkins APL/NOIRLab
Asteroid Dinkinesh's Dynamic History
Dinkinesh, with a diameter of nearly half a mile (720 meters), has revealed a dynamic history. The asteroid's surface features, including ridges and troughs, suggest a past filled with stress and transformation.
Researchers believe that thermal radiation over millions of years caused Dinkinesh to rotate faster, leading to centrifugal stresses that eventually shifted the asteroid into an elongated shape.
"We want to understand the strengths of small bodies in our solar system because that's critical for understanding how planets like Earth got here," explained Hal Levison, Lucy's principal investigator from the Southwest Research Institute.
If Dinkinesh was much weaker, resembling a fluid pile of sand, its particles would have gradually moved towards the equator and been flung off into orbit as it spun faster, NASA reports.
However, Dinkinesh held together for a longer period, suggesting it possesses rock-like strength. Nonetheless, the strength required to fragment a small asteroid like Dinkinesh is minuscule compared to most rocks found on Earth.
Keith Noll, project scientist for Lucy at NASA's Goddard Space Flight Center adds that the asteroid's trough structures suggest an abrupt failure, more akin to an earthquake with a sudden release of built-up stress, rather than a slow process.
During its dynamic history, a significant piece of rock likely broke free from Dinkinesh, forming a trough and sending debris into space.
Some of this debris fell back onto Dinkinesh's surface as boulders, creating a ridge structure, while other material coalesced to form Selam, a contact-binary moonlet. A study published May 29 in Nature by main author Levison and team takes note of these observations.
Selam, composed of two similarly sized lobes (750 feet and 690 feet wide), orbits Dinkinesh every 53 hours at a distance of about two miles (3.1 km).
Simone Marchi, deputy principal investigator for the Lucy mission explains that mall asteroids may shed material, which later ends up forming a small satellite or satellites. "The complex shape of Selam indicates that this process may occur multiple times," Marchi explains.
Future Missions
Dinkinesh, meaning "you are marvelous" in Amharic, is the Ethiopian name for the famous Lucy fossil, an Australopithecus specimen providing insight into human evolution. Selam, meaning "peace," is named after another Australopithecus fossil.
Looking ahead, Lucy will continue its journey, including a gravity assist flyby of Earth in December 2024, propelling it towards the asteroid Donaldjohanson in 2025 and then on to the Trojan asteroids beginning in 2027.
