Thermophysical Modeling of 20 Themis Family Asteroids with WISE/NEOWISE Observations

TL;DR

This study models the thermal properties of 20 Themis family asteroids using WISE/NEOWISE data, revealing their surface composition, roughness, and potential water-ice presence, contributing to understanding their origin and evolution.

Contribution

It applies advanced thermophysical modeling to a large asteroid family, providing new insights into their surface properties and thermal characteristics.

Findings

Average thermal inertia ~39.5 J m^{-2} s^{-1/2} K^{-1}

Geometric albedo ~0.067

Low surface roughness and mature regolith

Abstract

Themis family is one of the largest and oldest asteroid populations in the main-belt. Water-ice may widely exist on the parent body (24) Themis. In this work, we employ the Advanced Thermophysical Model as well as mid-infrared measurements from NASA's Wide-Field Infrared Survey Explorer to explore thermal parameters of 20 Themis family members. Here we show that the average thermal inertia and geometric albedo are ~$39.5\pm26.0 ~\rm J m^{-2} s^{-1/2} K^{-1}$ and $0.067\pm0.018$, respectively. The family members have a relatively moderate roughness fraction on their surfaces. We find that the relatively low albedos of Themis members are consistent with the typical values of B-type and C-type asteroids. As aforementioned, Themis family bears a very low thermal inertia, which indicates a fine and mature regolith on their surfaces. The resemblance of thermal inertia and geometric albedo of Themis members may reveal their close connection in origin and evolution. In addition, we present the compared results of thermal parameters for several prominent families.