Title: Interpretations of family size distributions: The Datura example,
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.