Low CO/CO2 ratios of comet 67P measured at the Abydos landing site by the Ptolemy mass spectrometer
1 Deparment of Physical Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK
2 Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
Received: 28 May 2015
Accepted: 27 July 2015
Comets are generally considered to contain the best-preserved material from the beginning of our planetary system, although the mechanism of their formation and subsequent evolution are still poorly understood. Here we report the direct in situ measurement of H2O, CO, and CO2 by the Ptolemy mass spectrometer onboard the Philae lander, part of the European Space Agency’s Rosetta mission, at the Abydos site of the Jupiter-family comet 67P/Churyumov-Gerasimenko. A CO/CO2 ratio of around 0.07 ± 0.04 is found at the surface of the comet, a value substantially lower than the one measured by ROSINA in the coma. Such a major difference is a potential indication of heterogeneity of the nucleus and not of changes in the CO/CO2 ratio of the coma with radial distance.
Key words: comets: general / comets: individual: 67P/Churyumov-Gerasimenko / space vehicles / space vehicles: instruments
© ESO, 2015