First in-situ detection of the CN radical in comets and evidence for a distributed source

TL;DR

This study presents the first in-situ detection of the CN radical in a comet's coma using high-resolution mass spectrometry from the Rosetta spacecraft, providing new insights into its distributed origin.

Contribution

It is the first to analyze CN radicals in a comet's coma in situ at high spatial and temporal resolution, revealing their distributed source.

Findings

CN radicals have a distributed source in comet 67P.

High-resolution data confirms in-situ detection of CN.

Results support a non-nuclear origin for CN radicals.

Abstract

Although the debate regarding the origin of the cyano (CN) radical in comets has been ongoing for many decades, it has yielded no definitive answer to date. CN could previously only be studied remotely, strongly hampering efforts to constrain its origin because of very limited spatial information. Thanks to the European Space Agency's Rosetta spacecraft, which orbited comet 67P/Churyumov-Gerasimenko for two years, we can investigate, for the first time, CN around a comet at high spatial and temporal resolution. On board Rosetta's orbiter module, the high-resolution double-focusing mass spectrometer DFMS, part of the ROSINA instrument suite, analyzed the neutral volatiles (including HCN and the CN radical) in the inner coma of the comet throughout that whole two-year phase and at variable cometocentric distances. From a thorough analysis of the full-mission data, the abundance of CN radicals in the cometary coma has been derived. Data from a close flyby event in February 2015 indicate a distributed origin for the CN radical in comet 67P/Churyumov-Gerasimenko.