On the origin of inner coma structures observed by Rosetta during a diurnal rotation of comet 67P/Churyumov-Gerasimenko

TL;DR

This study uses high-resolution simulations and observations to show that the anisotropic dust distribution and jet structures in comet 67P's inner coma originate from dust released across the entire sunlit surface, mainly from concave areas like pits and craters.

Contribution

It proposes a novel explanation that cometary jets result from dust released over the whole sunlit surface, not just localized sources, based on trajectory analysis and correlation with observations.

Findings

Dust released from entire sunlit surface explains coma anisotropy.

Jets form mainly from concave surface features like pits and craters.

Simulation predictions correlate strongly (~0.8) with observations during diurnal rotation.

Abstract

The Rosetta probe around comet 67P/Churyumov-Gerasimenko (67P) reveals an anisotropic dust distribution of the inner coma with jet-like structures. The physical processes leading to jet formation are under debate, with most models for cometary activity focusing on localised emission sources, such as cliffs or terraced regions. Here we suggest, by correlating high-resolution simulations of the dust environment around 67P with observations, that the anisotropy and the background dust density of 67P originate from dust released across the entire sunlit surface of the nucleus rather than from few isolated sources. We trace back trajectories from coma regions with high local dust density in space to the non-spherical nucleus and identify two mechanisms of jet formation: areas with local concavity in either two dimensions or only one. Pits and craters are examples of the first case, the neck region of the bilobed nucleus of 67P for the latter one. The conjunction of multiple sources in addition to dust released from all other sunlit areas results in a high correlation coefficient (~0.8) of the predictions with observations during a complete diurnal rotation period of 67P.