基于最新多源数据的嫦娥三号着陆区地层结构研究

The eruption phase and total volume of the mare basalt provides a basic thermal and lithogenesis constraint on the moon. Mare Imbrium is the largest impact basin of the lunar nearside. According to Wilhelms(1987), the formation age of imbrium basin is 3.85 Ga. The Mare basalts erupted periodically and filled the low-lying large impact basins and craters from Imbrian Period to Eratosthenian Period(Hiesinger et al., 2000; Hiesinger et al., 2010). Basing on crater size-frequency distribution data and spectral and morphological data, reseachers defined many homogeneous units in mare imbrium. These units shows differnent eruption ages between 2.01 and 3.57Ga, implying a trend that older basalts may be covered by younger basalts. For the total volumn, there are some methods to determin, such as crater excavation method, the craters partially filled wieh basalt. But the stratigraphy and the eruptive sequence of the basalt units still remain unclear. In our project, the data of the CE3 lunar penetrating radar will be used to obtain the subsurface stratification of the landing area, for CE-3 landing position is close to the boundary two basalt units. Using the CE-2 CCD image data and the Selene Multi-band imager data, we will define the units near the landing site again and estimate the age of the units. Based on these works, we will give a geological profile with fine stratigraphy stucture and the eruptive history of the landing area, giving a control point for the study of the basalt in the Mare Imbrium.

研究月海玄武岩喷发期次和规模能为月球的岩石成因学和热演化历史提供重要的约束条件。嫦娥三号着陆在雨海北部地区（44.12°N 19.50°W），该地区是晚雨海世至爱拉托辛纪的玄武岩大规模填充雨海盆地后形成的地质区域，保存有丰富的地层信息。前人对于玄武岩单元的划分、各单元表面年龄以及玄武岩的总体积有过大量的估算，但是对于各期次喷发规模和层序关系，由于缺乏就位探测数据，研究相对较少。本项目利用最新的光谱数据和嫦娥二号高分辨率影像数据，对着陆区附近的玄武岩单元重新进行划分和年龄计算；在此基础上解译嫦娥三号巡视器的测月雷达数据图像，处理获得着陆区玄武岩的分层和厚度信息；同时结合最后系统性地绘制出着陆区附近区域的玄武岩喷发期次、年龄、厚度、层序关系等的地质剖面图，为雨海地区的玄武岩覆盖规模提供可靠的控制点。

嫦娥三号着陆于雨海北部地区，接近新老两个玄武岩单元的分界处，对于着陆区的地层结构和月壤风化物结构的研究，对于理解雨海的形成和演化具有重要意义。本项目通过对嫦娥三号巡视器搭载的测月雷达数据的处理，结合月面影像数据，研究着陆点月壤层的介电常数、厚度信息，以及玄武岩单元的分层结构。研究发现，着陆区月壤介电常数随深度成线性变化，石块含量随深度明显增加，厚度较浅，大约在2.5~3米之间。着陆区的月面年龄比较年轻，受到的表面撞击、改造作用较少，表面覆盖的月壤厚度浅且含石块较多。对第一通道数据的研究并未发现有效的分层结构，表明最近一次玄武岩喷发规模较大，厚度至少大于雷达就位探测深度。