Research Article

Flux and composition of interstellar dust at Saturn from Cassini’s Cosmic Dust Analyzer

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Science  15 Apr 2016:
Vol. 352, Issue 6283, pp. 312-318
DOI: 10.1126/science.aac6397

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Cassini detects interstellar dust grains

The interstellar medium contains an array of small solid particles known as dust grains. Altobelli et al. used the dust analyzer on the Cassini probe to detect 36 interstellar dust grains as they passed by Saturn, and they measured the grains' elemental abundances. The results show that, remarkably, these grains lack carbon-bearing compounds and have been homogenized in the interstellar medium into silicates with iron inclusions.

Science, this issue p. 312


Interstellar dust (ISD) is the condensed phase of the interstellar medium. In situ data from the Cosmic Dust Analyzer on board the Cassini spacecraft reveal that the Saturnian system is passed by ISD grains from our immediate interstellar neighborhood, the local interstellar cloud. We determine the mass distribution of 36 interstellar grains, their elemental composition, and a lower limit for the ISD flux at Saturn. Mass spectra and grain dynamics suggest the presence of magnesium-rich grains of silicate and oxide composition, partly with iron inclusions. Major rock-forming elements (magnesium, silicon, iron, and calcium) are present in cosmic abundances, with only small grain-to-grain variations, but sulfur and carbon are depleted. The ISD grains in the solar neighborhood appear to be homogenized, likely by repeated processing in the interstellar medium.

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