Analysis of Hybrid Gas-Dust Outbursts Observed at 67P/Churyumov-Gerasimenko

Cometary outbursts offer a valuable window into the composition of comet nuclei with their forceful ejection of dust and volatiles in explosive events, revealing the interior components of the comet. Understanding how different types of outbursts influence the dust properties and volatile abundances, to better interpret what signatures can be attributed to primordial composition and what features are the result of processing, is an important task best undertaken with a multi-instrument approach. The European Space Agency Rosetta mission to 67P/Churyumov-Gerasimenko carried a suite of instruments capable of carrying out this task in the near-nucleus coma with unprecedented spatial and spectral resolution. In this work, we discuss two outbursts that occurred 2015 November 7 and were observed by three instruments on board: the Alice ultraviolet spectrograph, the Visual Infrared and Thermal Imaging Spectrometer, and the Optical, Spectroscopic, and Infrared Remote Imaging System. Together, the observations show that mixed gas and dust outbursts can have different spectral signatures representative of their initiating mechanisms, with the first outburst showing indicators of a cliff collapse origin and the second more representative of fresh volatiles being exposed via a deepening fracture. This analysis opens up the possibility of remote spectral classification of cometary outbursts with future work.

Automated summary

Cometary outbursts provide valuable insights into the composition of comet nuclei by forcefully ejecting dust and volatiles in explosive events. Understanding the influence of different outburst types on dust properties and volatile abundances is crucial for interpreting the signatures of primordial composition versus processing effects, and a multi-instrument approach is the best way to tackle this task. The analysis of two outbursts observed by instruments on board the Rosetta mission reveals that spectral signatures of mixed gas and dust outbursts may vary depending on their initiating mechanisms, opening up the possibility of remote spectral classification of cometary outbursts in future studies.