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Attogram Dust Cloud a Million Kilometers from Comet Halley

Kissel, Jochen; Utterback, Nyle G.

Particle-impact ion mass spectrometers carried on the Giotto and two Vega spacecraft missions to Comet Halley in 1986 produced unexpected signals almost one million kilometers from Halley which can be attributed to high number densities of dust particles with masses of order 10 to the -18 g. The data imply that up to several percent of the total m…