A new study challenges the long-held view of how binary asteroids form. For decades, the standard paradigm held that many of these systems arise when a rapidly spinning primary asteroid casts off material, which then reaccumulates into an elongated moon near the Roche limit.
Researchers now suggest that the puzzling configurations observed in some binary asteroids may instead be linked to a multi-satellite history. This alternative formation pathway could explain why some moons are not as elongated as the classic model predicts.
The findings, published in a recent study, reexamine the dynamics of these systems. Instead of a single shedding event, multiple smaller satellites may have coalesced or interacted over time, producing the diverse shapes and orbits seen today.
If validated, this model would reshape our understanding of asteroid evolution in the inner solar system. It could also influence how we interpret data from upcoming space missions focused on visiting and characterizing binary asteroids.
“This opens up new questions about how common these multi-satellite histories might be,” the study's lead author noted. Further observations are needed to distinguish between the two formation scenarios.