Diverse configurations of binary asteroids explained by multi-generation satellites

Binary asteroid systems are ubiquitous in the Solar System. Many of them originate from rotational breakup, where an asteroid’s spin-up triggers mass shedding and subsequent satellite formation from a transient debris disk. While prolate satellites on compact orbits are expected in this scenario, recent space missions revealed remarkable diversity of binary configurations, such as the contact-binary satellite Selam on a wide orbit around (152830) Dinkinesh. Here we show that multiple episodes of mass shedding and the resulting multi-generation satellites provide a unified framework for these diverse configurations. We find that a pre-existing satellite can strongly influence subsequent satellite formation pathways through disk-satellite and inter-satellite interactions. This mechanism explains the dynamical histories of the Dinkinesh system and several triple systems. Our analysis indicates that about 44% of known binaries have configurations indicative of multi-satellite histories, suggesting that a significantly greater diversity of binary asteroid configurations remains to be revealed. Binary asteroids are common, yet their diverse configurations remain mysterious. Here, the authors show how repeated mass shedding and satellite migration drive this diversity, explaining complex forms like contact-binary satellites.