Albedos and diameters of three Mars Trojan asteroids

TL;DR

This study measures the sizes and surface reflectivities of three Mars Trojan asteroids using infrared observations, providing insights into their composition and surface properties.

Contribution

First infrared-based size and albedo measurements of specific Mars Trojan asteroids, linking physical properties to their taxonomic classifications.

Findings

Eureka's diameter is approximately 1.28 km with a high albedo of 0.39.

1998 VF31's diameter is about 0.78 km with an albedo of 0.32.

2001 FR127 has a diameter less than 0.52 km and an albedo greater than 0.14.

Abstract

We observed the Mars Trojan asteroids (5261) Eureka and (101429) 1998 VF31 and the candidate Mars Trojan 2001 FR127 at 11.2 and 18.1 microns using Michelle on the Gemini North telescope. We derive diameters of 1.28, 0.78, and <0.52 km, respectively, with corresponding geometric visible albedos of 0.39, 0.32, and >0.14. The albedos for Eureka and 1998 VF31 are consistent with the taxonomic classes and compositions (S(I)/angritic and S(VII)/achrondritic, respectively) and implied histories presented in a companion paper by Rivkin et al. Eureka's surface likely has a relatively high thermal inertia, implying a thin regolith that is consistent with predictions and the small size that we derive.