Upper Limits for Emissions in the Coma of Comet 67P/Churyumov-Gerasimenko Near Perihelion as Measured by Rosetta's Alice Far-Ultraviolet Spectrograph

TL;DR

This study uses Rosetta's Alice spectrograph data to establish upper limits on emissions from various atomic and ionic species in comet 67P's coma near perihelion, enhancing understanding of its composition.

Contribution

The paper introduces automated spectral fitting software and provides the first comprehensive upper limits on multiple atomic emissions in the comet's coma during perihelion.

Findings

Set upper limits for 1 ion and 17 neutral species.

Compared cometary emissions to chondrites and solar abundances.

Analyzed over 70,000 spectral images from Rosetta.

Abstract

The Alice far-UV imaging spectrograph (700-2050 A) acquired over 70,000 spectral images during Rosetta's 2-year escort mission, including over 20,000 in the months surrounding perihelion when the comet activity level was highest. We have developed automated software to fit and remove ubiquitous H, O, C, S, and CO emissions from Alice spectra, along with reflected solar continuum and absorption from gaseous H2O in the comet's coma, which we apply to a "grand sum" of integrations taken near perihelion. We present upper limits on the presence of one ion and 17 neutral atomic species for this time period. These limits are compared to results obtained by other Rosetta instruments where possible, as well as to CI carbonaceous chondrites and solar photospheric abundances.