Instantaneous thermally-driven erosion can explain dearth of dark near-Sun asteroids

TL;DR

This study demonstrates that intense solar heating can rapidly erode dark asteroids near the Sun, explaining their scarcity and observed mass loss, through vacuum irradiance experiments on CI meteorite simulants.

Contribution

It provides experimental evidence that thermal erosion at close solar distances can destroy dark asteroids within minutes, clarifying their dearth near the Sun.

Findings

Dark asteroids are destroyed within minutes at 0.2 au in irradiance experiments.

The destruction explains the scarcity of dark near-Sun asteroids.

Mass loss rates of 322P/SOHO 1 align with thermal erosion predictions.

Abstract

Recent models of the near-Earth asteroid population show that asteroids must be super-catastrophically destroyed when they evolve to orbits with perihelion passages well inside of Mercury's orbit. The heliocentric distances at which the disruptions typically occur are tens of solar radii, which is too far from the Sun for asteroids to be destroyed by sublimation and tidal disruption. The typical disruption distance also appears to be larger for darker asteroids. Here, by carrying out irradiance experiments in vacuum that replicate the conditions in the near-Sun environment, we show that CI meteorite simulants are destroyed within minutes when exposed to the level of solar irradiance encountered at heliocentric distances of up to about 0.2 au. Our results provide an explanation for the scarcity of dark, carbonaceous asteroids with perihelion distances less than 0.2 au, and for the observed mass-loss rate of the asteroid-like object 322P/SOHO~1 assuming its composition is similar to CI carbonaceous chondrites.