Nanophase materials including silicates, aluminosilicates, and iron oxides are widespread on Mars. These minerals are important because they likely represent a solid-phase record of ancient climatic conditions on the martian surface. Identification and characterization of nanophase compounds is technically challenging due to the small size and poorly ordered nature of these materials, particularly because their chemical compositions can vary widely.This study presents spectra of several synthetic allophane and imogolite samples with a range of chemical compositions that are typical of the natural variability of allophanic materials. These samples were formed under controlled conditions and have been thoroughly characterized in terms of chemical composition and short-range structure.Analyses confirmed that the synthetic materials were allophane and imogolite and were structurally similar to previously studied natural and synthetic examples of these phases. NMR and XAFS data indicated that high-Al proto-imogolite allophanes were similar in structure to imogolite but were less well ordered, and supported the proposed nanoball structures based on rolled octahedral Al sheets. Increasing Si content in allophane produced increasing tetrahedral Al substitution as well as polymerized Si chain structures at Al-Si mole ratios of 1:1, and sheets and possible framework structures at Al-Si mole ratios of 1:2. Fe in allophanes and imogolites substituted exclusively for octahedral Al.Reflectance spectra of the synthetic allophanes and imogolites were comparable to previously analyzed samples. Variations in Fe content of allophane and imogolite resulted in some observable changes in visible/near-infrared (VNIR) reflectance spectra, but these changes were not detectable in emission spectra. Emission spectra of the samples suggest that variations in Al-Si ratio of allophanes should be detectable using remotely sensed data. Because allophanes with different Al-Si ratios typically form in very different environments, this could be significant for interpretation of formation conditions on Mars, with high-Al compositions suggesting possible tephra weathering and high-Si compositions indicating possible formation from thermal waters.

中文翻译：

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富铁含量可变的别铝和石云母样品的光谱分析，用于表征火星上不良的结晶成分

包括硅酸盐，铝硅酸盐和氧化铁在内的纳米相材料在火星上分布广泛。这些矿物很重要，因为它们可能代表火星表面古代气候条件的固相记录。纳米相化合物的鉴定和表征在技术上具有挑战性，因为这些材料的体积小且排列不规则，尤其是因为它们的化学组成可能差异很大。典型的同色材料的自然变异性。这些样品是在受控条件下形成的，并已根据化学组成和短程结构进行了全面表征。分析证实，合成材料是别铝镁石和伊莫高石，并且在结构上与先前研究的这些相的天然和合成实例相似。NMR和XAFS数据表明，高Al的原发烟云母别铝烷在结构上与发烟云石相似，但排列较不规则，并支持了基于轧制八面体Al片材的拟议纳米球结构。铝脲烷中Si含量的增加会导致Al-Si摩尔比为1：1的四面体Al取代量增加以及聚合的Si链结构，以及Al-Si摩尔比为1：2时的片状结构和可能的骨架结构。别铝和单铝辉石中的铁仅取代八面体Al。合成的脲原和单光辉石的反射光谱与先前分析的样品相当。脲基铝石和卵黄铁矿中Fe含量的变化导致可见/近红外（VNIR）反射光谱出现一些可观察到的变化，但在发射光谱中无法检测到这些变化。样品的发射光谱表明，应使用遥感数据检测出脲丙烷的铝硅比变化。因为具有不同Al-Si比例的脲基甲酸酯通常在非常不同的环境中形成，这对于解释火星上的形成条件可能具有重要意义，其中高Al成分表明可能存在特非拉风化，而高Si成分表明可能从热水中形成。样品的发射光谱表明，应使用遥感数据检测出脲丙烷的铝硅比变化。因为具有不同Al-Si比例的脲基甲酸酯通常在非常不同的环境中形成，这对于解释火星上的形成条件可能具有重要意义，其中高Al成分表明可能存在特非拉风化，而高Si成分表明可能从热水中形成。样品的发射光谱表明，应使用遥感数据检测出脲丙烷的铝硅比变化。因为具有不同Al-Si比例的脲基甲酸酯通常在非常不同的环境中形成，这对于解释火星上的形成条件可能具有重要意义，其中高Al成分表明可能存在特非拉风化，而高Si成分表明可能从热水中形成。