Dynamical horseshoe orbit as the explanation to a circumsolar dust ring in the neighbourhood of Mercury?

In this study, we investigate the spatial and density distribution of zodiacal cloud dust in the inner solar system, with the focus being on Mercury's orbit and the formation and persistence of the circumsolar dust ring discovered in 2018 in the immediate vicinity of the Sun. Previous knowledge of Mercury's orbital environment suggests that, due to its proximity to the Sun and hence its extremely high perturbation effects, this environment may not contain matter in the longer term. This picture seems to have become more uncertain. In our model, we have considered the constrained three-body problem of the Sun-Mercury system along the Lagrangian libration points, which due to the degree of stability and the 1:1 mean motion resonance and the continuous perturbative effects of the perturbed dust particle motion within the stable region we assumed a horseshoe orbit. According to our model, the horseshoe orbit undergoes a strong deformation due to the proximity of the Sun at the near-solar boundary of the stable region, where the Poynting-Robertson effect causes dust particles of different grain sizes to continuously fall out of the stable region and spiral into the Sun. To represent the fate of the different grain sizes, a circumsolar dust ring was set up in three scenarios, in all three of which a smaller compact ring of larger grains appeared.

Using comet 67P/Churyumov-Gerasimenko as a mass reference, the number of comets needed to fill the toroidal volume of the orbit of Mercury and the time scale required to do so were quantified. As a final result, our model predicts that the instrumentally discovered circumsolar dust ring is distributed along a highly deformed horseshoe track, which can persist in a continuously replenished dynamical system such that the dust grains that constitute it are replaced on a century-to-millennium scale.