¹Frans J.M. Rietmeijer
¹Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico, USA

In Stardust tracks C2044,0,38, C2044,0,39, and C2044,0,42 (Brennan et al. 2007) and Stardust track 10 (this work) gold is present in excess of its cosmochemical abundance. Ultra-thin sections of allocation FC6,0,10,0,26 (track 10) show a somewhat wavy, compressed silica aerogel/silica glass interface which challenges exact location identification, i.e., silica glass, compressed silica aerogel, or areas of overlap. In addition to domains of pure silica ranging from SiO2 to SiO3 glass, there is MgO-rich silica glass with a deep metastable composition, MgO = 14 ± 6 wt%, due to assimilation of Wild 2 Mg-silicate matter in silica melt. This magnesiosilica composition formed when temperatures during hypervelocity capture reached >2000 °C followed by ultrafast quenching of the magnesiosilica melt when it came into contact with compressed aerogel at ~155 °C. The compressed silica aerogel in track 10 has a continuous Au background as result of the melting point depression of gold particles

Reference
Rietmeijer FJM (2016) At the interface of silica glass and compressed silica aerogel in Stardust track 10: Comet Wild 2 is not a goldmine. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12608]
Published by arrangement with John Wiley & Sons