The Dynamical Origins of the Dark Comets and a Proposed Evolutionary Track

TL;DR

This paper investigates the origins of dark comets, proposing they result from rotational fragmentation of rubble pile objects, and traces their source to the inner main belt, indicating the presence of volatiles near Earth.

Contribution

It introduces a model linking dark comets to rotational fragmentation and uses dynamical simulations to identify their main source regions.

Findings

Dark comets are consistent with rubble pile structures.

Most originate from the $ u_6$ resonance in the inner main belt.

One dark comet likely originated from the outer main belt.

Abstract

So-called 'dark comets' are small, morphologically inactive near-Earth objects (NEOs) that exhibit nongravitational accelerations inconsistent with radiative effects. These objects exhibit short rotational periods (minutes to hours), where measured. We find that the strengths required to prevent catastrophic disintegration are consistent with those measured in cometary nuclei and expected in rubble pile objects. We hypothesize that these dark comets are the end result of a rotational fragmentation cascade, which is consistent with their measured physical properties. We calculate the predicted size-frequency distribution for objects evolving under this model. Using dynamical simulations, we further demonstrate that the majority of these bodies originated from the $\nu_6$ resonance, implying the existence of volatiles in the current inner main belt. Moreover, one of the dark comets, (523599) 2003 RM, likely originated from the outer main belt, although a JFC origin is also plausible. These results provide strong evidence that volatiles from a reservoir in the inner main belt are present in the near-Earth environment.