{'fraction_non_alphanumeric': 0.025332097621254247, 'fraction_numerical': 0.017608897126969416, 'mean_word_length': 5.086466165413534, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Comparison of Carbon XANES Spectra from an Iron Sulfide from Comet Wild 2 with an Iron Sulfide Interplanetary Dust Particle

Introduction: Among one of the first particles removed from the aerogel collector from the Stardust sample return mission was an ~ 5 μm sized iron sulfide. The majority of the spectra from 5 different sections of this particle suggests the presence of aliphatic compounds. Due to the heat of capture in the aerogel we initially assumed these aliphatic compounds were not cometary but after comparing these results to a heated iron sulfide interplanetary dust particle (IDP) we believe our initial interpretation of these spectra was not correct. It has been suggested that ice coating on iron sulfides leads to aqueous alteration in IDP clusters which can then lead to the formation of complex organic compounds from unprocessed organics in the IDPs similar to unprocessed organics found in comets [1]. Iron sulfides have been demonstrated to not only transform halogenated aliphatic hydrocarbons but also enhance the bonding of rubber to steel [2,3]. Bromfield and Coville (1997) demonstrated using Xray photoelectron spectroscopy that “the surface enhancement of segregated sulfur to the surface of sulfided precipitated iron catalysts facilitates the formation of a low-dimensional structure of extraordinary properties” [4]. It may be that the iron sulfide acts in some way to protect aliphatic compounds from alteration due to heat. Samples: Five ultramicrotomed sulfur embedded sections from particle C2044,0,36,1 from Comet Wild 2 were analyzed. This particle was located in track 36. L2009 is a cluster IDP from cluster 10 collected in the Earth’s atmosphere at a height of ~20 km. One ultramicrotomed sulfur embedded section of the iron sulfide from L2009 cluster 10 was analyzed. Result: The iron sulfide from this IDP cluster was ~ 3 x 5 μms in size. Besides sulfur and iron; nickel, silicon, magnesium, calcium, aluminum, chromium, and phosphorus were found in the cluster. This iron sulfide was analyzed using both transmission electron microscopy (TEM) with electron diffraction; and scanning transmission x-ray microscopy (STXM) with carbon x-ray absorption near edge structure (XANES) spectroscopy. The TEM results showed a complete rim of magnetite surrounding the iron sulfide core suggesting significant heating upon atmospheric entry. Typically, IDPs showing full-developed magnetite rims also exhibit Zn-loss [5] which occurs above ~1100 degrees C in pulse heating of primitive meteorites [6]. The STXM carbon map (fig. 1a) shows that much of the carbon associated with this particle was pushed off of the particle during microtoming. This is an effect we have observed in other IDP sections. The carbon XANES spectrum from this area suggests a carbon species similar to an amorphous carbon compound with a carbonyl bond to it, (fig.2); an oxygenated amorphous carbon. A C=O bond typically absorbs in the 288-289 eV range. Amorphous carbon has a very broad peak around 285 eV suggesting multiple absorption peaks due to amorphous carbon’s different bonding configurations of sp2 C atoms and the tendency of these bonds to gather into pi bond clusters of different bonding configurations [7].