Revisiting Advanced Thermal Physical Model: New Perspectives on Thermophysical Characteristics of (341843) 2008 EV5 from Four-bands WISE Data with Sunlight-Reflection Model

TL;DR

This study refines the thermophysical understanding of asteroid 2008 EV5 using an improved model that incorporates sunlight reflection, WISE data, and shape modeling, revealing its low thermal inertia, high surface roughness, and possible origin from the main belt.

Contribution

We developed an enhanced ATPM considering sunlight reflection and applied it to WISE data, providing new insights into the asteroid's surface properties and origin.

Findings

Low thermal inertia (~110 J m^-2 s^-1/2 K^-1) suggests space weathering.

High surface roughness similar to Bennu and Ryugu.

Approximately 6.1% probability of main belt origin.

Abstract

In this paper, we investigate thermophysical characteristics of near-Earth asteroid (341843) 2008 EV5, based on our improved Advanced Thermal Physical Model (ATPM) by considering the contribution of sunlight-reflection for rough surface, along with four wavebands observations from Wide-field Infrared Survey Explorer (WISE) and the radar-derived shape model. Here we derive that 2008 EV5 has a relatively low thermal inertia of $\Gamma=110 _{-12}^{+40}\rm~J m^{-2} s^{-1/2} K^{-1}$ but a high roughness fraction. The geometric albedo and effective diameter are then constrained to be $p_v=0.095_{-0.003}^{+0.016}$ and $D_{\rm eff}=431_{-33}^{+6}\rm~m$, respectively. The low thermal inertia indicates that 2008 EV5 may have undergone sufficient space weathering over secular evolution. The high roughness may have resemblances to the appearances of Bennu and Ryugu recently observed by spacecrafts, where a great number of boulders are widely distributed on the asteroid's surface. Moreover, we numerically perform 1000 backward simulations of 2008 EV5's cloned orbits within 1 Myr to explore its origin, and present a probability of $\sim6.1\%$ that the asteroid originates from the main belt. Finally, we estimate that the mean grain size of the surface ranges from 0.58 to 1.3 mm, and infer that it is unlikely to find water ice on most area of 2008 EV5, but there may exist water ice on high-latitudes near polar region.