ESA’s Cometary Mission Rosetta – Re‐Characterization of the COSAC Mass Spectrometry Results

International audienceThe most pristine material of the Solar System is assumed to be preserved in comets in the form of dust and ice as refractory matter. ESA’s mission Rosetta and its lander Philae had been developed to investigate the nucleus of comet 67P/Churyumov-Gerasimenko in situ. Twenty-five minutes after the initial touchdown of Philae on the surface of comet 67P in November 2014, a mass spectrum was recorded by the time-of-flight mass spectrometer COSAC onboard Philae. The new characterization of this mass spectrum through non-negative least squares fitting and Monte Carlo simulations reveals the chemical composition of comet 67P. A suite of 12 organic molecules, 9 of which also found in the original analysis of this data, exhibit high statistical probability to be present in the grains sampled from the cometary nucleus. These volatile molecules are among the most abundant in the comet’s chemical composition and represent an inventory of the first raw materials present in the early Solar System