Laboratory simulation of cometary dust collection and analysis

An experiment for the in situ analysis of cometary dust grains during a rendezvous mission to a comet consists of three elements: (1) Substrate preparation, i.e. cleaning of the substrates in order to reduce the background contamination, (2) dust collection and (3) chemical analysis. All three elements have been simulated in a laboratory experiment. Combined heat treatment (up to 200°C) and surface sputtering of the gold substrates by a glow discharge reduced the surface contamination of Na, Al and K by a factor of 1000 and that of all other contaminants below the detection threshold. During the sputtering of the substrates they acquired a surface roughness of ∼5 μm, which improved their collection efficiency for dust particles. Dust particles were shot onto those substrates at speeds up to 200 m s −1. Chemical analysis using secondary ion mass spectroscopy (SIMS) provided information on elemental abundances, the molecular composition and isotopic ratios of selected elements even at a surface dust coverage of 10 −2–10 −4. Both technical details of the new equipment and results of the first investigation on target surface cleaning and SIMS analysis of dust particles will be reported.