Mid-infrared spectral variability for compositionally similar asteroids: Implications for asteroid particle size distributions
Mid-infrared spectral variability for compositionally similar asteroids: Implications for asteroid particle size distributions
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DOI：
10.1016/j.icarus.2010.01.011
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发表时间：
2009-09
期刊：
影响因子：
3.2
通讯作者：
P. Vernazza;B. Carry;J. Emery;J. Hora;D. Cruikshank;R. Binzel;J. Jackson;J. Helbert;A. Maturilli
中科院分区：
文献类型：
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作者：
P. Vernazza;B. Carry;J. Emery;J. Hora;D. Cruikshank;R. Binzel;J. Jackson;J. Helbert;A. Maturilli
我们报告了8颗S类型小行星的中红外光谱(IRTF和斯皮策数据)之间的意外变化，对这些小行星的所有其他遥感解释(例如，VNIR光谱、反照率)都产生了类似的成分。利用它们的中红外光谱进行成分拟合只会产生令人惊讶的替代结论：(1)这些天体在“成分上并不相似”，因为它们的主要表面矿物(橄榄石和辉石)的丰度彼此相差35%，(2)碳质球粒陨石和普通球粒陨石与每种小行星光谱都提供了同样好的匹配。在Ramsey和Christensen(Ramsey，M.S.，Christensen，P.R.)的实验室工作之后[1998]。J.地球物理。第103,577-596号决议)，我们将这种变化解释为表面颗粒大小的差异和/或空间风化过程的影响在物理上造成的。我们的结果表明，观测到的小行星一定覆盖着非常细的尘埃(<；5μm)，这些尘埃掩盖了一些主要和最次要的光谱特征。我们推测，成分分析可能会通过包含各种特征良好的光谱(例如，橄榄石、斜辉石、长石、铁等)的光谱库来改进。从非常细的粉末中获得。除了颗粒尺寸效应外，空间风化过程也可能导致光谱对比度的降低。这可以通过新的实验室辐射实验直接进行测试。
We report an unexpected variability among mid-infrared spectra (IRTF and Spitzer data) of eight S-type asteroids for which all other remote sensing interpretations (e.g. VNIR spectroscopy, albedo) yield similar compositions. Compositional fitting making use of their mid-IR spectra only yields surprising alternative conclusions: (1) these objects are not “compositionally similar” as the inferred abundances of their main surface minerals (olivine and pyroxene) differ from one another by 35% and (2) carbonaceous chondrite and ordinary chondrite meteorites provide an equally good match to each asteroid spectrum. Following the laboratory work of Ramsey and Christensen (Ramsey, M.S., Christensen, P.R. [1998]. J. Geophys. Res. 103, 577–596), we interpret this variability to be physically caused by differences in surface particle size and/or the effect of space weathering processes. Our results suggest that the observed asteroids must be covered with very fine (<5μm) dust that masks some major and most minor spectral features. We speculate that the compositional analysis may be improved with a spectral library containing a wide variety of well characterized spectra (e.g., olivine, orthopyroxene, feldspar, iron, etc.) obtained from very fine powders. In addition to the grain size effect, space weathering processes may contribute as well to the reduction of the spectral contrast. This can be directly tested via new laboratory irradiation experiments.