Asteroid Family Associations Of Active Asteroids

Active asteroids have orbits similar to those of asteroids but exhibit activity similar to comets.To understand the distribution of water ice in the solar system,extensive research on active asteroids is required as a reference point.The collisional history of the main asteroid belt can be revealed by studying asteroid families,which consist of asteroids with similar orbits,compositions,and spectral types formed by catastrophic collisions of parent asteroids.Therefore,investigating the relationship between active asteroids and families can help in the search for new active asteroids and expand the active asteroid database.In this study,we used the Hierarchical Clustering method and the Selective Backward Integration method to identify linked families and young families for all known main belt active asteroids(MBAAs).This study comprises 34 active asteroids,including 9 main-belt comets,4 impact fragmentation asteroids,10 active asteroids with rotational instability,and 11 active asteroids with unknown activation mechanisms.We found 5 new candidate sub-groups for MBAAs,including the Brueghel family associated with 176P/LINEAR,the 324P group associated with 324P/La Sagra,the G1 group associated with P/2016 G1,the Tutenchamun family associated with(62412)2000 SY178,and the O1 group associated with P/2020 O1.Additionally,we reported 4 new family associations between 259P/Garradd and the Adeona family,(596)Schiela and the candidate Scheila family,P/2019 A4 and the Jones family,and P/2021 A5 and the Interamnia family.Stable main-belt comets(MBCs)are associated with known or candidate young and primitive families,while unstable MBCs are associated with primitive families and higher eccentricities that result in excavating deeply buried water-ice.Impact-disrupted asteroids may be linked with young families or families with lower inclinations.Eight out of ten rotationally disrupted asteroids are driven by both rapid rotation and sublimation,with six likely associated with young and primitive families dominated by primitive C-type asteroids.Rotationally disrupted asteroids in the middle and outer main belt may be candidate MBCs and potential binary asteroids.These findings suggest that MBCs activity is connected to the compositions and activity triggering mechanism,while disrupted asteroids appear to be more complicated,especially for activities driven by multiple triggering mechanisms.To further constrain the native distribution of main-belt ice in the solar system,future research should focus on the currently unknown activity mechanism of MBAAs,which could help in the search for new MBAAs in constrained primitive families.This paper also aims to determine the effective diameter of active asteroid 311P/PANSTARRS by analyzing its relationship with its population and exploring its long-term dynamical evolution.The paper also discusses changes in the long-term motion of 311P/PANSTARRS caused by the Yarkovsky effect.By assuming different surface compositions,this simulation introduced semimajor axis drift by propagating orbits of test particles,and discussed the effects of other factors such as close encounters,meteoroid impacts,and the YORP effect on the orbit evolution of 311P/PANSTARRS.Additionally,we estimated the timescale for 311P/PANSTARRS to reach its rotation period of splitting limit.The simulation results showed that the Yarkovsky effect may cause 311P/PANSTARRS to exit from the resonance region faster than a purely gravitational model.After approximately 10 Myr,311P/PANSTARRS is expected to exit its current resonance region,and may become a Mars-crossing asteroid due to the diurnal Yarkovsky effect via the v6 secular resonance,provided that its surface is covered by a regolith layer.Our conclusion is that even when accounting for the Yarkovsky effect and the YORP effect,311P/PANSTARRS will remain stable for at least 10 million years.Furthermore,the YORP effect is not expected to significantly impact the semi-major axis drift of 311P/PANSTARRS.