The effect of the dust size distribution on asteroid polarization

TL;DR

This study develops a theoretical model to understand how dust size distribution influences asteroid polarization and confirms that polarization is primarily determined by surface composition, not dust particle size.

Contribution

The paper introduces a new theoretical framework linking asteroid polarization to surface composition, independent of dust size distribution, supported by observational data.

Findings

Polarization is controlled by surface mineralogy and chemistry.

The polarization-phase curve slope relates to albedo regardless of dust size.

Surface composition, not dust size, dominates polarization characteristics.

Abstract

We have developed a theoretical description of how of an asteroid's polarization-phase curve will be affected by the removal of the dust from the surface due to a size-dependent phenomenon such as radiation pressure-driven escape of levitated particles. We test our calculations against new observations of four small (D ~ 1 km) near-Earth asteroids [(85236), (142348), (162900) and 2006 SZ_217] obtained with the Dual Beam Imaging Polarimeter on the University of Hawaii's 2.2 m telescope, as well as previous observations of (25143) Itokawa and (433) Eros. We find that the polarization of the light reflected from an asteroid is controlled by the mineralogical and chemical composition of the surface and is independent of dust particle. The relation between the slope of the polarization-phase curve beyond the inversion angle and the albedo of an asteroid is thus independent of the surface regolith size distribution and is valid for both Main Belt and Near-Earth asteroids.