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Asteroid pairs are genetically related asteroids that recently separated (

Though pairs of dynamically associated asteroids in the Main Belt have been identified and studied for over a decade, very few pair systems have been identified in the near-Earth asteroid population. We present data and analysis that supports the existence of two genetically related pairs in near-Earth space. The members of the individual systems, 2015 EE7 – 2015 FP124 and 2017 SN16 – 2018 RY7, are found to be of the same spectral taxonomic class, and both pairs are interpreted to have volatile-poor compositions. In conjunction with dynamical arguments, this suggests that these two systems formed via YORP spin-up and/or dissociation of a binary precursor. Backwards orbital integrations suggest a separation age of <10 kyr for the pair 2017 SN16 – 2018 RY7, making these objects amongst the youngest multiple asteroid systems known to date. A unique separation age was not realized for 2015 EE7 – 2015 FP124 due to large uncertainties associated with these objects' orbits. Determining the ages of such young pairs is of great value for testing models of space weathering and asteroid spin-state evolution. As the NEO catalog continues to grow with current and future discovery surveys, it is expected that more NEO pairs will be found, thus providing an ideal laboratory for studying time dependent evolutionary processes that are relevant to asteroids throughout the Solar System. • Two new asteroid pairs have been identified in the near-Earth object population. • Spectral data show that members of these systems have the same spectral type. • These two pairs likely formed via YORP spin-up and/or binary dissociation. • Orbit integrations of pair 2017 SN16–2018 RY7 suggest a separation age < 10 kyr. • Continued growth of the NEO catalog will lead to identification of more NEO pairs. [ABSTRACT FROM AUTHOR]

We studied asteroid clusters suggesting a possibility of at least two disruption events in their recent history (≤ 5 Myr). We searched for new members of known asteroid pairs and clusters and we verified their membership using backward orbital integrations. We found four asteroid clusters, namely the clusters of (11842) Kap'bos, (14627) Emilkowalski, (63440) 2001 MD30 and (157123) 2004 NW5 that show at least two secondary separation events that occurred at significantly different times. We considered a possible formation mechanism for these clusters: The parent of an asteroid cluster was spun up to its critical rotation frequency, underwent a rotation fission and was slowed down by escape of the newly formed secondary/ies. Then the YORP effect spun up the primary again and it reached its critical rotation frequency and underwent another fission. We created a simple model to test whether the scenario of two rotation fission events of a parent primary induced via the YORP effect is possible for the four clusters. We obtained a good agreement between the model and the cluster properties for the clusters of Kap'bos and (63440). For the cluster of Emilkowalski, our model explained the unusually slow rotation of the primary. However, the time needed for the primary to reach its critical frequency after the first fission event was predicted to be too long by a factor of several. We suspect, considering also its D type taxonomic classification and the existence of a dust band associated with the cluster, that the asteroid Emilkowalski may actually be a cometary nucleus. Regarding the cluster of (157123), the final rotational frequency of the primary after the last fission event predicted by our model is in a good agreement with the observed rotation frequency of (157123). However, a separation of the older secondary is not possible in our model due to the deficiency of free energy needed for an escape of the large secondary. This could be due to an error in the H value of the secondary or the possibility that we did not find the real primary of this cluster. • Ages of genetically related asteroid clusters were studied. • At least two separation events were recognized in four asteroid clusters. • Backward orbital integration method was used for age estimations. • Scenario of two rotational fission induced by YORP effect was considered and tested. • Asteroid pairs and cluster may form inside existing asteroid pairs and clusters. [ABSTRACT FROM AUTHOR]