First statistical analysis of 5000 mass spectra of cometary grains obtained by PUMA 1 (Vega 1) and PIA (Giotto) impact ionization mass spectrometers in the compressed modes

Abstract

Impact ionization mass spectrometers have been flown on board the space vehicles Giotto (instrument PIA), Vega 1 and Vega 2 (instruments PUMA 1 and 2). All three instruments obtained a large collection of mass spectra of individual cometary dust particles in the mass range 3×10^-16 - 3×10^-10g. Spectra from PUMA 2 are still being recovered from data transmission problems, and only results from PUMA 1 and PIA are presented. A large fraction of particles (≡30%) are dominated by light elements (H, C, O, and N, or "CHON"). Approximately 35% of particles can be interpreted as minerals with a compositional range similar to that encountered in carbonaceous chondrites. The remaining 35% appear to be mixtures in varying amounts of these two major components. Statistically significant variations have been observed as a function of time.