Fakultät für Physik und Astronomie
STEPHEN PHILLIPS hostreviews.co.uk / UNSPLASH

Interstellar grains analysed by the Cassini and Stardust space missions

Mario Trieloff , Inst. Geowiss., Universität Heidelberg, D

In 1992 the Ulysses spacecraft detected a stream of interstellar dust grains passing our solar system. The Stardust mission succeeded in collecting and identifying seven particles of likely interstellar origin. They are diverse in elemental composition, crystal structure, and size. The presence of crystalline grains and multiple iron-bearing phases, including sulfide, in some particles indicates that individual interstellar particles diverge from representative models of interstellar dust inferred from astronomical observations and theory, but the relatively large grains found are biased to the high mass tail of the interstellar population and may not be truly representative. In-situ analyses of the Cosmic Dust Analyser on-board the Cassini spacecraft obtained between 2004 and 2013 yielded the first mass spectra of grains from the Local Interstellar Cloud. These 36 interstellar grains can be clearly identified and distinguished from Saturn bound dust by their direction and high velocity, and their mean mass is consistent with the typical ISD size inferred from astronomical observations. 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 approximately 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.

Heidelberg Joint Astronomical Colloquium
19 Jun 2018, 16:15
Philosophenweg 12, großer Hörsaal

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