Many asteroids evolve onto orbits with very small perihelion distances due to repeated gravitational interactions with Jupiter. Although dynamical models predict a substantial population of these near-Sun asteroids, far fewer are observed, suggesting that many are destroyed during close approaches to the Sun. 

Objectives

The primary goal of this project was to search for observational signatures of near-Sun surface processes that could explain the apparent depletion of asteroids at small perihelion distances. Specifically, I aimed to observe asteroids with a perihelion distance q<0.15 au, measure their optical colors, and assess whether their surface properties show evidence of thermal alteration or resurfacing. Key challenges included limited observing windows, extreme viewing geometries, and separating surface evolution from differences in orbital history. We used a wide variety of ground-based optical telescopes over three years to achieve these observations.

Results

We successfully observed the majority of known asteroids with q<0.15, significantly expanding the available dataset for this population. The asteroids display a wide range of colors, reflecting diverse orbital histories and physical processes. However, a slight preference toward bluer colors (Figure 1) suggests that resurfacing mechanisms, such as thermal fatigue caused by intense temperature cycling near the Sun, may be common. These findings support the idea that near-Sun processes actively modify asteroid surfaces and may contribute to their eventual disintegration.