Exploring the Early Solar System with Cometary Gases: Observations of Spontaneous Activity Around Comet 67P/Churyumov-Gerasimenko Post-Perihelion with the R-Alice Ultraviolet Spectrograph

Undergraduate Honors Thesis

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Citeable URL: https://scholar.colorado.edu/concern/undergraduate_honors_theses/2z10wq93x

Abstract

The Rosetta Alice (R-Alice) ultraviolet spectrograph on the European Space Agency Rosetta spacecraft, currently escorting the comet 67P/Churyumov-Gerasimenko in its orbit around the Sun, has observed the activity of the comet since encounter in August 2014. Fortuitous observations taken in October and November 2015, two and three months after perihelion respectively, show large increases in the Lyman-β, OI 1304, CII 1335, OI] 1356, and CI 1657 atomic emission lines that indicate gas outbursts. Due to the electron impact on gases in the cometary coma the data is compared to measured cross sections and line ratios to put constraints on outburst composition. Analysis of these emission lines and the ratios indicates that each primary outburst was driven by molecular oxygen and followed by a smaller secondary outburst. In both cases the secondary outburst contained a different composition of CO₂ or H₂O than in the primary outburst. These observations support the findings of Bieler et al. 2015 and detail the need for a formation mechanism that traps O₂ in comets during formation.

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