月球典型撞击坑溅射物研究及对月球地质编图的意义

A study of lunar typical crater ejecta and its implications for lunar geologic mapping

撞击坑是月表最典型的地质单元,其溅射物作为撞击坑的坑外组成部分可分布到距离坑中心10个直径距离之外的区域,因此撞击溅射物也是月球地质编图中最重要的表达要素之一。本文使用月球勘测轨道器(LRO)的激光高度计(LOLA)数据、广角相机(WAC)影像、窄角相机(NAC)影像以及Clementine的UVVIS多光谱数据,研究了哥白尼纪正面月海区直径31km的Kepler撞击坑和背面月陆区直径30km的Necho撞击坑。哥白尼纪撞击坑溅射沉积物可以分为三个相:连续溅射沉积相(CE)、不连续溅射沉积相(DE)和辐射纹(CR)。连续溅射沉积相分布在最大约2.6个半径范围之内,不连续溅射沉积相分布在最大近11个半径范围之内,辐射纹分布在最大近29个半径范围之内。本文强调了多源数据结合在识别撞击坑溅射沉积物中的作用,对Kepler坑和Necho坑溅射沉积物进行了填图,不对称分布的特征表明这两个坑可能形成于倾斜撞击。

Crater is the most typical geologic unit on the lunar surface. As the outer part of a crater, the ejecta often occurs even beyond ten crater diameters, which makes it one of the most important features during lunar geologic mapping. By using of the lunar orbiter laser altimeter （LOLA） data, wide-angle camera （WAC） images and narrow-angle camera （NAC） images in Lunar Reconnaissance Orbiter （LRO） mission and Clementine UVVIS muhispectral data, we studied the 31km in diameter crater Kepler which locates in the nearside mare region and 30km in diameter crater Necho which locates in the farside land region, both of them belong to Copernican. Copernican crater ejecta can be divided into three faces, which are continuous ejecta deposits （CE）, discontinuous ejecta deposits （DE） and crater ray （CR）. CE is distributed in a max distance of about 2. 6 radii. DE is distributed in a max distance of almost 11 radii, and CR is distributed in a max distance of about 29 radii. This paper stresses the significance of the combination of multi-source data in recognizing the ejecta deposits. Multi-source data are used in mapping the ejecta of crater Kepler and crater Necho. The asymmetric distributions of these two craters ＇ ejecta indicate that they were formed in an oblique impact respectively.