Composition of comet Halley dust particles from Vega observations

Abstract : The dust impact mass analyser (PUMA) carried by the spacecraft Vega 1 and Vega 2 has provided the first direct measurements of the physical and chemical properties of cometary dust. Particles of mass <10⁻¹⁴ g are much more abundant than was predicted by models1. Most of the particles are rich in light elements such as H, C, N and O, lending support to models that describe cometary material as consisting of radiation-processed ices. Three examples of mass spectra for typical particle compositions are shown.