Iron oxides in comet 81P/Wild 2 |
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| Authors: | John C BRIDGES Mark J BURCHELL Hitesh C CHANGELA Nick J FOSTER J Alan CREIGHTON James D CARPENTER Steve J GURMAN Ian A FRANCHI Henner BUSEMANN |
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| Institution: | 1. Department of Physics and Astronomy, Space Research Centre, University of Leicester, Leicester LE1 7RH, UK;2. Centre for Astrophysics and Planetary Science, School of Physical Sciences, University of Kent, Canterbury, Kent CT2 7NH, UK;3. ESTEC, Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands;4. Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK;5. Planetary and Space Science Research Institute, Open University, Walton Hall, Milton Keynes MK7 6AA, UK;6. School of Earth, Atmospheric and Earth Sciences, University of Manchester, Manchester M13 9PL, UK |
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| Abstract: | Abstract– We have used synchrotron Fe‐XANES, XRS, microRaman, and SEM‐TEM analyses of Stardust track 41 slice and track 121 terminal area slices to identify Fe oxide (magnetite‐hematite and amorphous oxide), Fe‐Ti oxide, and V‐rich chromite (Fe‐Cr‐V‐Ti‐Mn oxide) grains ranging in size from 200 nm to ～10 μm. They co‐exist with relict FeNi metal. Both Fe‐XANES and microRaman analyses suggest that the FeNi metal and magnetite (Fe2O3FeO) also contain some hematite (Fe2O3). The FeNi has been partially oxidized (probably during capture), but on the basis of our experimental work with a light‐gas gun and microRaman analyses, we believe that some of the magnetite‐hematite mixtures may have originated on Wild 2. The terminal samples from track 121 also contain traces of sulfide and Mg‐rich silicate minerals. Our results show an unequilibrated mixture of reduced and oxidized Fe‐bearing minerals in the Wild 2 samples in an analogous way to mineral assemblages seen in carbonaceous chondrites and interplanetary dust particles. The samples contain some evidence for terrestrial contamination, for example, occasional Zn‐bearing grains and amorphous Fe oxide in track 121 for which evidence of a cometary origin is lacking. |
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