Early Activity of Churyumov-Gerasimenko: ROSINA/RTOF Results
Peter Wurz1, Kathrin Altwegg2, Hans R Balsiger3, Sébastien Gasc3, Andre Galli4, Martin Rubin4, Annette Jäckel3, Lena Le Roy2, Ursina Calmonte2, Chia-yu Tzou3, Urs A. Mall5, Axel Korth5, Björn Fiethe6, Johan MSJ De Keyser7, Jean-Jacques Berthelier8, Henri Rème9, Tamas I Gombosi10, Stephen A Fuselier11 and ROSINA Team, (1)University of Bern, Space Research and Planetary Sciences, Bern, Switzerland, (2)University of Bern, Bern, Switzerland, (3)University of Bern, Physikalisches Institut, Bern, Switzerland, (4)University of Bern, Physics Institute, Space Research and Planetary Sciences, Bern, Switzerland, (5)Max Planck Institute for Solar System Research, Katlenburg-Lindau, Germany, (6)Technical University of Braunschweig, Braunschweig, Germany, (7)Belgian Institute for Space Aeronomy, Brussels, Belgium, (8)LATMOS Laboratoire Atmosphères, Milieux, Observations Spatiales, Paris Cedex 05, France, (9)IRAP, Institut de Recherche en Astrophysique et Planétologie, Toulouse, France, (10)University of Michigan, Climate and Space Sciences and Engineering, Ann Arbor, United States, (11)Southwest Research Institute, San Antonio, United States
Abstract:
The European Space Agency’s Rosetta spacecraft is now close to the comet 67P/Churyumov-Gerasimenko (67P/C-G). On board is the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) instrument suite. ROSINA consists of two mass spectrometers, the Double Focusing Mass Spectrometer (DFMS) and the Reflectron-type Time-Of-Flight (RTOF), as well as the COmet Pressure Sensor (COPS).
The first signal with ROSINA/RTOF of the gaseous environment of the comet was a significant increase in water density observed on DOY 218.1 of 2014 (at 3.5 AU) by RTOF above the gaseous envelope of the Rosetta spacecraft. A similar density increase is observed by COPS at the same time. A preliminary analysis shows that the water density is nH2O ≈ 1012 m–3 at 100 km distance from the comet (located at 3.5 AU from the Sun). This gives a density at the surface of nH2O ≈ 6.4·1015 m–3 and a vertical column density of water of NCH2O ≈ 6.5·1018 m–2. Assuming an active area of 4% we arrive at a production rate of QH2O ≈ 5.8·1024 mole s–1. These values are preliminary and will be refined by forthcoming observations. Other than water, no signal related to cometary activity could be observed above the molecular background from the spacecraft at present, e.g. cometary CO and CO2 are not observed in the RTOF data so far. This hints at a possible deficiency of carbon bearing compounds in the comet.
