Stardust glass: Indigenous and modified comet Wild 2 particles

Abstract

There is no evidence among the collected comet dust for interstellar glass with embedded metals and sulfides. There is, however, ample evidence for melting of the smallest, sub-micrometer comet particles of nanometer-scale grains similar to those in the matrix of chondritic aggregate IDPs, including pyrrhotite. Massive patches of Mg-SiO, Al-SiO, or Ca-Si-O glass are incorporated in the familiar, vesicular Si-rich glass are melted Wild 2 silicates. Magnesiosilica glass has a deep metastable eutectic smectite-dehydroxylate composition. It indicates that very high temperatures well above the liquidus temperatures of forsterite were achieved very rapidly and were followed but ultrarapid quenching. This predictable and systematic response is not limited to Mg-silicates, and recognizing this phenomenon among massive glass will provide a means to complete the reconstruction of this comet's original minerals, as well as constrain the physiochemical environment created during aerogel melting and evaporation.

Understanding the mechanisms of formation of nanophase compounds from Stardust: Combined experimental and observational approach

“…These regions are probably remnants from cometary silicates and/or amorphous grains (Leroux et al. 2008b; Rietmeijer 2009b,c). Although we have not attempted to synthesize materials with these compositions, formation of sulfides from Ca‐ and Mg‐bearing gases will be explored experimentally in future studies.…”

“…For details, see Zolensky et al. (2006, Supplemental data) and for details on the high‐resolution TEM (HRTEM) analyses, see Rietmeijer (2009b). Analyses of the Stardust samples were conducted at the Electron Microbeam Analysis Facility at the Department of Earth and Planetary Science, University of New Mexico.…”

“…2008; Tomeoka et al. 2008; Rietmeijer 2009b; Stoldona et al. 2009; Velbel and Harvey 2009; Bridges et al.…”

“…Some Wild 2 grains (larger than ∼0.5 μm) preserved along track styli or embedded in the low‐Mg silica glass appear to have survived intact. On the other hand, the thermal regimes in the bulbous parts caused instant melting and quenching, and/or evaporation‐condensation of the smallest comet dust grains and pure silica aerogel (Rietmeijer 2009b,c). The Preliminary Examination Team studies ( Science , 2006, 314:1711–1739) reported inclusions in the vesicular low‐Mg silica glass whose textures are reminiscent of GEMS (glass with embedded metals and sulfides; Bradley 1994) that are found in the matrix of porous aggregate interplanetary dust particles (IDPs) (cf.…”

Fine‐grained material encased in microtracks of Stardust samples

“…; Leroux et al. , ; Rietmeijer ; Leroux ). Most of these samples show CI‐like composition, including sulfur, suggesting an impact melting of a very primitive material (Leroux et al.…”