In 2022, NASA’s DART spacecraft collided with the moon by an asteroid named Dimorphos, disintegrating the moon and creating a large crater. The impact reshaped the Moon so dramatically that it derailed from its original evolutionary progression.
According to scientists, Dimorphos may begin to chaotically „fall” in an attempt to return to gravitational equilibrium with its parent asteroid, Didymos.
A new study from the University of Maryland provides details on the post-impact observations and describes possible implications for future asteroid research.
A striking effect was that DART altered the pattern of demorphoses. First, the shape of the asteroid moon is oblate. After the impact, it expanded further.
Derek Richardson, professor of astronomy at the University of Maryland and chair of the DART investigation task force, said, „We expected Dimorphos to have a prolate frontal impact because we believed that normally the central body of the Moon would gradually accumulate material ejected from a primary body like Didymos. It naturally tends to form an elongated body that always has its long axis pointing toward the main body.”
„But this result contradicts that idea and suggests that something more complex is at work here. Also, an impact-induced change in Dimorphos’ shape may have changed how it interacts with Didymos.
Although DART only hits the Moon, the Moon and its asteroid are gravitationally bound together. Debris from the impact also upset their balance, causing the moon, Dimorphos, to rapidly orbit its asteroid Didymos. Interestingly, Didymos did not change shape, showing that it was solid enough to remain solid even after losing the material to form its moon.
According to Richardson, DiMorphos’ changes have important implications for future exploration efforts, including one planned for the European Space Agency’s Didymos system in October 2024.
„At first, Dimorphos was probably very loose, and had one side toward the main body, Didymos, just as Earth’s moon always points one face toward our planet.” Richardson explained. „Right now, it’s not aligned, which means it can wobble back and forth in its orientation. Dimorphos can also be 'dumping,’ meaning we can cause it to rotate chaotically and unexpectedly.
If Dimorphos is still spinning, the team is now waiting to see when the debris will be cleared and when it will return to its previous steady state.
A significant question now is whether Dimorphos is stable enough to land the spacecraft and deploy more research equipment. It may take a hundred years to see significant changes, but the impact takes only a few years.
Understanding how long it takes for a demorphose to regain stability will provide important insights into its internal structure and aid future asteroid deflection efforts.
Scientists hope that Hera will provide more information about the impact of DART. In late 2026, Hera will reach the binary asteroid system containing Dimorphos and Didymos for the first time to assess the internal properties of the two asteroids, providing a detailed analysis of the DART mission and its implications for the future.
Journal Note:
- Derek Richardson et al. Motion state of Didymos system before and after DART impact. Journal of Planetary Science. DOI 10.3847/PSJ/ad62f5