Surface Properties of Near-Sun Asteroids

TL;DR

This study examines the surface properties of near-Sun asteroids, analyzing their colors, spectral slopes, and rotation periods to understand the effects of extreme solar heating and other processes on their surfaces.

Contribution

It provides the first comprehensive observational dataset of near-Sun asteroid surface colors and rotation periods, highlighting the influence of near-Sun processes on surface alteration.

Findings

Near-Sun asteroids tend to have bluer colors than typical NEAs.

Large scatter in colors suggests diverse histories and compositions.

No clear correlation found between colors and other properties.

Abstract

Near-Earth Asteroids (NEAs) with small perihelion distances reach sub-solar temperatures of > 1000 K. They are hypothesized to undergo "super-catastrophic" disruption, potentially caused by near-Sun processes such as thermal cracking, spin-up, meteoroid impacts, and subsurface volatile release; all of which are likely to cause surface alteration, which may change the spectral slope of the surface. We attempted to observe 35 of the 53 known near-Sun asteroids with q < 0.15 au from January 2017 to March 2020 to search for trends related to near-Sun processes. We report the optical colors and spectral slopes of 22 objects that we successfully observed and the measured rotation periods for three objects. We find the distribution of colors to be overall bluer than the color distribution of NEAs, though there is large overlap. We attribute large scatter to unknown dynamical histories and compositions for individual objects, as well as competing surface altering processes. We also investigated potential correlations between colors and other properties (e.g., perihelion distance, Tisserand parameter, rotation period), and searched for evidence of activity. Finally, we have compiled all known physical and dynamical properties of these objects, including probabilistic source regions and dwell times with q < 0.15 au.