Global classification of lunar reflectance spectra obtained by Kaguya (SELENE): Implication for hidden basaltic materials
Global classification of lunar reflectance spectra obtained by Kaguya (SELENE): Implication for hidden basaltic materials
复制标题
Kaguya（SELENE）获得的月球反射光谱的全局分类：对隐藏玄武岩材料的启示
DOI：
10.1016/j.icarus.2018.11.016
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发表时间：
2018
期刊：
影响因子：
3.2
通讯作者：
M. Ohtake
中科院分区：
文献类型：
--
作者：
Hareyama;M.;Y. Ishihara;H. Demura;N. Hirata;C. Honda;S. Kamata;Y. Karouji;J. Kimura;T. Morota;H. Nagaoka;R. Nakamura;S. Yamamoto;Y. Yokota;M. Ohtake
在统一的分类准则下，应用K-means和ISODATA非监督分类方法，建立了月球吸收光谱的全球分类图。这些光谱是由月亮女神号（SELENE）月球轨道器航天器上的光谱剖面仪（SP）获得的。光谱主要通过K均值方法分为七个光谱组：K1，K2，K3，K4，K5，K6和K7。然后，每个K-means组被划分为66个总类的ISODATA方法。的K1和K3组被分为21和14类，分别，其平均光谱是高钙辉石（HCP）丰富的相比，其他组。这两个群体主要位于月海和火山碎屑沉积。然而，虽然K1群主要位于大月海中心附近，但K3群主要位于小月海和大月海边缘。K2组包含八个类别，并显示出平均光谱，如低钙辉石（LCP），在丰富的，这主要是在南极-艾特肯（SPA）盆地和海岸的Mare Frigoris。K5（8类）、K6（2类）和K7（3类）组表示吸收比K1、K2和K3组更浅的平均光谱（波长在0.9 μ m和1.2 μ m之间）。这些群位于高地地区，K5群位于高海拔地区，如新鲜陨石坑。K6群分布在近侧高原地区，K7群分布在远侧高原地区。K4群有9个类，显示平均光谱，如K1/K2/K3和K5/K6/K7的混合物，并且这些类位于Mare/SPA和高地之间的边界附近。此外，一类是独立定义的，而不使用K-均值和ISODATA，因为它的光谱是不适合自动无监督分类。ISODATA类的平均光谱不仅显示了属于光谱组的主要主体物质的特征，而且还显示了附近区域其他组物质对该主体物质的微小影响。这种影响被认为是由该位置的物质与附近区域的喷出物的水平物质混合引起的。然而，偶尔受K1/K3群影响的K4、K5和K6群的ISODATA类在地理上聚集在远离K1/K3区域的区域。有些星团的位置与著名的隐藻和小型火山碎屑沉积物的位置相对应。另一方面，它们中的一些位置也包含隐藏的地下玄武岩物质的候选者，例如根据最近的月球重力异常估计的未发现的cryptomare，岩脉和岩床。这种一致性表明，通过垂直方向上发生的物质混合，隐藏着玄武岩物质。除了已知的隐藻外，集群的总面积约为已知隐藻的2倍，约占暴露海总面积的20%。除了已知的隐脉岩外，隐藏的玄武岩物质的总体积估计为104至106 km3，这取决于隐脉岩和岩脉/岩床之间相对丰度的假设。该体积与已知的隐马粪相当，约为暴露母马的10%。
A global classification map of lunar absorption spectra is developed under unified classification criteria by applying the K-means and ISODATA unsupervised classification methods. The spectra were obtained by the Spectral Profiler (SP) onboard the Kaguya (SELENE) lunar orbiter spacecraft. The spectra are mostly categorized into seven spectral groups by the K-means method: K1, K2, K3, K4, K5, K6, and K7. Then, each K-means group is divided into 66 total classes by the ISODATA method. The K1 and K3 groups are classified into 21 and 14 classes, respectively, for which the average spectra are high-calcium pyroxene (HCP)-abundant compared to the other groups. Both groups are mainly located on maria and pyroclastic deposits. However, while the K1 group can be found primarily near the center of large maria, the K3 group can be found mainly at small maria and the margins of large maria. The K2 group contains eight classes and shows average spectra, such as low-calcium pyroxene (LCP), in abundance, which are found mainly on the South Pole-Aitken (SPA) basin and on the coast of Mare Frigoris. The K5 (eight classes), K6 (two classes) and K7 (three classes) groups indicate average spectra with shallower absorption (between 0.9 µm and 1.2 µm wavelength) than those of the K1, K2, and K3 groups. These groups are located in highland regions, and the K5 group is located in high-albedo regions, such as fresh craters. The K6 group is found on nearside highland areas and the K7 group is found on farside highland areas. The K4 group with nine classes shows average spectra, such as mixtures of K1/K2/K3 and K5/K6/K7, and these classes are located around boundaries between mare/SPA and highland. In addition, one class is independently defined without using K-means and ISODATA because its spectra are unsuitable for automatic unsupervised classification. However, this class is still geologically meaningful.The average spectra of the ISODATA classes show not only the characteristics of the major host material belonging to a spectral group, but they also show the small influence of materials from other groups in nearby regions on that host material. This influence is considered to be caused by horizontal material mixing of materials in that location with the ejecta from nearby regions. However, occasionally the ISODATA classes of the K4, K5, and K6 groups influenced by the K1/K3 groups are clustered geographically in regions far from the K1/K3 regions. Some locations of the clusters correspond to locations of the well-known cryptomaria and small pyroclastic deposits. On the other hand, some locations of them also contain candidates of hidden subterranean basaltic materials, such as undiscovered cryptomare, dike, and sill estimated based on recent lunar gravitational anomalies. This agreement suggests to be appeared hidden basaltic materials by the material mixing occurring vertically. The total area of the clusters except for known cryptomaria is approximately two times larger than that of the known cryptomaria, and this area reaches approximately 20% of the total area of exposed maria. The total volume of hidden basaltic materials, except for the known cryptomaria, is estimated to be 104to 106km3, depending on assumptions of the relative abundance between cryptomare and dike/sill. This volume is comparable to that of the known cryptomaria and approximately 10% of that of the exposed mare.