Isotope measurements of a comet by the Ptolemy instrument on Rosetta

Morse, Andrew; Andrews, Dan; Barber, Simeon; Leese, Mark; Morgan, Geraint; Pillinger, Colin; Sheridan, Simon and Wright, Ian (2009). Isotope measurements of a comet by the Ptolemy instrument on Rosetta. In: Joint European and National Astronomy Meeting, 21-22 Apr 2009, Hatfield, UK.

URL: http://star.herts.ac.uk/ewass/abstracts.pdf

Abstract

The aim of the ESA Rosetta mission is to make long term measurements of a comet as it approaches the sun from 3.5 AU to 1.4 AU over a period of at least six months and includes the Philae lander as well as the orbiter spacecraft. Ptolemy, on board Philae, is a GC-MS instrument designed for the analysis of cometary volatiles, organic materials and silicates. The objectives of Ptolemy are to provide a complete description of the nature and distribution of light elements (H, C, N and O) present in the nucleus of the comet, as well as determining their stable isotopic compositions. Ptolemy also aims to provide ground-truth measurements of those volatiles that are subsequently detected further out from the nucleus in the coma. Samples from the surface and sub-surface, collected by the lander drilling system (SD2), are heated in an oven and can be injected into one of three gas chromatography columns (GC) for analysis by the mass spectrometer. Accurate isotopic analysis is achieved by chemical processing before and/or after the GC columns and by direct comparison with reference materials of known isotopic composition. The Rosetta spacecraft, launched in 2004, is currently about half way through its 6.5 billion km, 10 year journey to comet P67/Churyumov-Geriasemnko. Operations of the Ptolemy mass spectrometer during spacecraft checkout and preparation for the asteroid Steins flyby have shown that the Ptolemy instrument is operational and should be capable of meeting its science aims. The next major milestone for Rosetta is the flyby of asteroid Lutetia in July 2010 during which Ptolemy will by operating to attempt to detect any exosphere.

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