Interpretations of family size distributions: The Datura example

TL;DR

This paper investigates the size-frequency distribution of the young Datura asteroid family, comparing it to other families, and explores how observational biases and impact processes like spall cratering influence the observed distributions.

Contribution

It provides the first detailed analysis of the Datura family's size distribution, highlighting the role of observational bias and proposing spall cratering as a key impact process.

Findings

Datura's size distribution appears shallower due to observational bias.

When accounting for parent body size, Datura's distribution aligns with typical asteroid families.

Spall cratering may explain the observed bump in the size distribution.

Abstract

Young asteroid families are unique sources of information about fragmentation physics and the structure of their parent bodies, since their physical properties have not changed much since their birth. Families have different properties such as age, size, taxonomy, collision severity and others, and understanding the effect of those properties on our observations of the size-frequency distribution (SFD) of family fragments can give us important insights into the hypervelocity collision processes at scales we cannot achieve in our laboratories. Here we take as an example the very young Datura family, with a small 8-km parent body, and compare its size distribution to other families, with both large and small parent bodies, and created by both catastrophic and cratering formation events. We conclude that most likely explanation for the shallower size distribution compared to larger families is a more pronounced observational bias because of its small size. Its size distribution is perfectly normal when its parent body size is taken into account. We also discuss some other possibilities. In addition, we study another common feature: an offset or "bump" in the distribution occurring for a few of the larger elements. We hypothesize that it can be explained by a newly described regime of cratering, "spall cratering", which controls the majority of impact craters on the surface of small asteroids like Datura.