Are fractured cliffs the source of cometary dust jets ? Insights from OSIRIS/Rosetta at 67P

TL;DR

This study uses high-resolution imaging and 3D reconstruction to investigate the origins of dust jets on comet 67P, proposing that active cliffs are the primary source of these jets and influence surface erosion.

Contribution

It provides observational evidence linking cometary jets to active cliffs, introducing a model that attributes jet formation to cliff erosion, a novel insight into comet surface activity.

Findings

Jets originate from areas with sharp topography.

Active cliffs are the main source of jets.

Cliffs contribute to surface erosion on comets.

Abstract

Dust jets, i.e. fuzzy collimated streams of cometary material arising from the nucleus, have been observed in-situ on all comets since the Giotto mission flew by comet 1P/Halley in 1986. Yet their formation mechanism remains unknown. Several solutions have been proposed, from localized physical mechanisms on the surface/sub-surface (see review in Belton (2010)) to purely dynamical processes involving the focusing of gas flows by the local topography (Crifo et al. 2002). While the latter seems to be responsible for the larger features, high resolution imagery has shown that broad streams are composed of many smaller features (a few meters wide) that connect directly to the nucleus surface. We monitored these jets at high resolution and over several months to understand what are the physical processes driving their formation, and how this affects the surface. Using many images of the same areas with different viewing angles, we performed a 3-dimensional reconstruction of collimated jets, and linked them precisely to their sources on the nucleus. Results.We show here observational evidence that the Northern hemisphere jets of comet 67P arise from areas with sharp topographic changes and describe the physical processes involved. We propose a model in which active cliffs are the main source of jet-like features, and therefore the regions eroding the fastest on comets. We suggest that this is a common mechanism taking place on all comets.