Fitting Cometary Sampling and Composition Mass Spectral Results Using Non-negative Least Squares: Reducing Detection Ambiguity for In Situ Solar System Organic Compound Measurements

Abstract

The chemistry occurring in the universe generates a huge variety of organic compounds abiotically. Significant progress has been made in understanding the types and distributions of these compounds in various planetary, asteroidal, cometary, nebular, and molecular cloud environments. One of the most exciting recent discoveries was the detection of low-molecular-weight organic species native to the surface of comet 67P/Churyumov-Gerasimenko by the cometary sampling and composition experiment that was aboard the Philae lander of the European Space Agency. The identities of these species were estimated using a simple hand-fitting method. Here, we use a more rigorous statistical method to fit the same data and find that there is some variance between results obtained using the two methods. This paper offers recommendations to improve the numerical methods for fitting of mass spectra, which would lead to more confident identification of ambiguous-mass compounds. Such methods may also help maximize the gains of future sampling-driven space missions, to Europa, Titan, Mars and its moons, comets, and asteroids, by filling in gaps in current scientific knowledge regarding electron impact mass spectra of ambiguous-mass compounds.