A comparative analysis of the outer-belt primitive families

TL;DR

This study compares physical properties of several primitive asteroid families in the outer belt, revealing diversity in hydration and spectral features that inform about their formation and the early Solar System conditions.

Contribution

It provides a comprehensive analysis combining new spectroscopic data with literature, highlighting differences among asteroid families in hydration and spectral characteristics.

Findings

Themis and Hygiea families show similar hydration levels.

Ursula and Lixiaohua are redder and lack hydrated members.

Veritas has the highest fraction of hydrated asteroids.

Abstract

Context. Asteroid families are witnesses to the intense collisional evolution that occurred on the asteroid belt. The study of the physical properties of family members can provide important information about the state of differentiation of the parent body and provide insights into how these objects were formed. Several of these asteroid families identified across the main belt are dominated by low-albedo, primitive asteroids. These objects are important for the study of Solar System formation because they were subject to weaker thermophysical processing and provide information about the early conditions of our planetary system. Aims. We aim to study the diversity of physical properties among the Themis, Hygiea, Ursula, Veritas, and Lixiaohua families. Methods. We present new spectroscopic data, combined with a comprehensive analysis using a variety of data available in the literature, such as albedo and rotational properties. Results. Our results show that Themis and Hygiea families, the largest families in the region, present similar levels of hydration. Ursula and Lixiaohua families are redder in comparison to the others and present no sign of hydrated members based on the analysis of visible spectra. Conversely, Veritas presents the highest fraction of hydrated members. Conclusions. This work demonstrates a diverse scenario in terms of the physical properties of primitive outer-belt families, which could be associated with dynamical mixing of asteroid populations and the level of differentiation of the parental body.