First Measurements of the Surface Composition of 67p Using the Ptolemy Mass

Introduction: Launched in 2004, and having awoken from deep space hibernation early in 2014, the Rosetta spacecraft [1] arrived at the comet designated 67P/Churyumov-Gerasimenko [2] on 6 August 2014. The spacecraft is currently in orbit around the comet and will hopefully continue to provide high quality science data for several more months to come. On 12 November 2014 the Philae lander element of the mission [3] was successfully deployed to the surface of the comet. Following the initial touchdown the so-called “First Science Sequence” was initiated. One of the instruments that was operational during this time was Ptolemy, a gas chromatograph-mass spectrometer system. We have previously described some of the operations that were planned to take place both before and after the landing [4, 5]. Ptolemy was primarily designed to undertake elemental and isotopic analyses of surface materials. But, as was witnessed during the flyby of asteroid 21 Lutetia, it can also be operate in a remote, stand-alone capacity, i.e. in space, as opposed to being on a cometary surface [6,7]. Herein we describe some of the results that were acquired as Rosetta approached the comet and, ultimately, as Philae made contact with the surface.