# Asteroid cratering families: recognition and collisional interpretation

## TL;DR

This paper investigates asteroid cratering families using proper elements, proposing a quantitative definition, analyzing their properties, and identifying multiple collisional events and dynamical mechanisms affecting their evolution.

## Contribution

It introduces a new quantitative criterion for classifying cratering families and provides detailed analysis of their compositional and dynamical properties, including multiple collision scenarios.

## Key findings

- Identified 25 asteroid families with over 100 members.
- Confirmed multiple cratering events in three families.
- Proposed a double collision origin for family 20.

## Abstract

We continue our investigation of the bulk properties of asteroid dynamical families identified using only asteroid proper elements (Milani et al. 2014) to provide plausible collisional interpretations. We focus on cratering families consisting of a substantial parent body and many small fragments. We propose a quantitative definition of cratering families based on the fraction in volume of the fragments with respect to the parent body; fragmentation families are above this empirical boundary. We assess the compositional homogeneity of the families and their shape in proper element space by computing the differences of the proper elements of the fragments with respect to the ones of the major body, looking for anomalous asymmetries produced either by post-formation dynamical evolution, or by multiple collisional/cratering events, or by a failure of the Hierarchical Clustering Method (HCM) for family identification. We identified a total of 25 dynamical families with more than 100 members ranging from moderate to heavy cratering. For three families (4, 15 and 283) we confirm the occurrence of two separate cratering events. For family 20, we propose a double collision origin, not previously identified. In four cases (31, 480, 163 and 179) we performed a dedicated search for dynamical resonant transport mechanisms that could have substantially changed the shape of the family. By using a new synthetic method for computation of secular frequencies, we found possible solutions for families 31, 480, and 163, but not for family 179, for which we propose a new interpretation, based on a secular resonance contaminating this family: the family of 179 should be split into two separate clusters, one containing (179) itself and the other, family (9506) Telramund, of fragmentation type, for which we have computed an age.