Research explains unusual shapes of certain asteroids and suggests these bizarre forms may be more common than previously thought.
A new study sheds light on the peculiar shapes of certain asteroids, like Dimorphos and Selam, which have long puzzled astronomers. Traditionally, binary asteroids—pairs of asteroids that revolve around each other—are expected to form with shapes resembling elongated footballs. However, Dimorphos, the target of NASA's 2022 DART mission, and Selam, a moonlet of asteroid Dinkinesh, defy these expectations with their distinct "watermelon" and bilobate shapes, respectively.
John Wimarsson, lead author of the study from the University of Bern, explained that conventional models for asteroid formation couldn't account for these unusual shapes. To address this, Wimarsson and his team developed detailed computer simulations to explore how the shapes of moonlets form based on their distance from the parent asteroid and the dynamics of collisions within a debris disk.
The study, published in *Icarus*, identified two main factors influencing a moonlet's shape: the gravitational pull of the parent asteroid and the nature of collisions in the surrounding debris disk. The researchers found that moonlets forming within the Roche limit of their parent asteroid tend to acquire prolate shapes, while those forming beyond this limit are more likely to develop oblate forms. Additionally, the angle and nature of collisions between precursor moonlets play a crucial role in shaping these bodies.
The findings suggest that such odd-shaped moonlets might be more common than previously recognized, but current observational techniques might overlook them due to a bias against detecting oblate shapes. This research not only clarifies the formation processes of these intriguing asteroids but also indicates that the diversity of asteroid shapes in our solar system may be greater than expected.
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