• Smelting of Fe-bearing glass during hypervelocity capture in aerogel

      Marcus, M. A.; Fakra, S.; Westphal, A. J.; Snead, C. J.; Keller, L. P.; Kearsley, A.; Burchell, M. J. (The Meteoritical Society, 2008-01-01)
      Hypervelocity capture of material in aerogel can expose particles to high transient temperatures. We tested some of the possible effects of capture by using a light-gas gun to shoot particles of basalt glass into aerogel at 6.1 km s^(-1). Using synchrotron-based micro-X-ray absorption spectroscopy (micro-XAS), we find that the starting material, in which the Fe was trivalent, is chemically reduced to divalent. In addition, some fragments were chemically reduced so that they contained Fe0 in a form spectroscopically consistent with a mixture of two forms of iron carbide (cohenite and haxonite). The carbon presumably originated from organic impurities in the aerogel. High-resolution transmission electron microscopy (HRTEM) imaging shows the presence of Fe-rich crystalline nanoparticles. A similar species has been found in actual Stardust material, suggesting that smelting effects occurred during capture and should be taken into account when interpreting data on Stardust samples.