In 2022, NASA’s Double Asteroid Redirection Test (DART) spacecraft collided with an asteroid moon called Dimorphos, causing significant deformation including the creation of a large crater and reshaping of the moon, derailing it from its original evolutionary progression. Researchers believe that Dimorphos may begin to tumble chaotically in an attempt to move back into gravitational equilibrium with its parent asteroid named Didymos. Despite some unexpected findings, pre-impact predictions about how DART would change the movement of Didymos and its moon were largely correct, providing insights into how asteroids and other small bodies evolve over time. A study led by Derek Richardson, published in Planetary Science Journal on August 23, 2024, detailed post-impact observations and outlined possible implications for future asteroid research.
One surprising observation was the significant change in Dimorphos’ shape following the impact with DART. Originally oblate, the asteroid moon became more prolate after the impact, contrary to expectations based on gradual accumulation of material shed off of a primary body like Didymos. The impact with DART also changed the interaction between Dimorphos and Didymos, shortening Dimorpho’s orbit around its parent asteroid. The research team noted that while DART only hit the moon, the moon and the main body are connected through gravity, and the debris scattered by the spacecraft played a role in disturbing the equilibrium between Dimorphos and Didymos. Didymos’ shape remained unchanged, indicating the larger asteroid is firm and rigid enough to maintain its form despite losing mass to create its moon.
According to Richardson, Dimorphos’ changes have significant implications for future exploration efforts, including the European Space Agency’s planned follow-up mission to the Didymos system in October 2024. The impact from DART knocked Dimorphos out of its original alignment, causing potential wobbling in its orientation and resulting in possible chaotic and unpredictable rotation or tumbling. The research team is waiting to see when the debris will clear from the system, whether Dimorphos is still tumbling, and when it will eventually regain its previous stability. Understanding the time it takes for Dimorphos to stabilize will provide valuable insights into its internal structure and inform future efforts to deflect hazardous asteroids.
Richardson and his team are looking to the Hera mission, planned for late 2026, to provide more information about DART’s impact and its implications. Hera will assess the internal properties of both Dimorphos and Didymos for the first time, offering a more detailed analysis of the DART mission and its significance for future asteroid research. The insights gained from DART and the subsequent studies help researchers calibrate their efforts to defend Earth against potential threats from asteroids or comets. This research into complex gravitational physics informs strategies for planetary defense and enhances our understanding of the potential risks posed by external threats. Ultimately, DART has provided valuable data and lessons that improve our readiness to protect the planet from potential asteroid impacts.