月表高程分布特征及其分级标准初探

月球是地球的唯一天然卫星,也是现阶段深空探测的主要天体。月表形貌研究有助于了解月球的状态、结构和组成,能够为探究月球起源和演化等科学问题提供直接、可靠的证据。与地貌分类相比,月貌研究起步较晚,发展较为缓慢。尽管月貌研究已取得了一定进展,但月球形貌分类过程中仍旧缺乏对于形貌指标,如高程等的应用,对于形貌特征的描述仍存在部分缺失。本文通过分析月球表面高程的整体特征以及月海、撞击坑、南极艾肯盆地等典型地质构造单元的高程特征,认为-2500 m等高线能够较好的区分月海内部区域;-1500 m等高线能够较好的区分月海区域与月陆区域;1000 m等高线与南极艾肯盆地边界拟合程度较好;3000 m等高线能够较好地突出月陆地区撞击坑的边界。在此基础上,提出以-2500 m、-1500 m、1000 m、3000 m 4个高程值作为月球形貌分类体系中的高程分类标准,将月球表面划分为极低海拔、低海拔、中海拔、高海拔和极高海拔5个形貌类型。

Distribution characteristics and classification schemes of lunar surface elevation

The moon is the only natural satellite of the earth and the main celestial body in deep space exploration at current stage. The study on lunar surface morphology can not only help understand the structure and composition of the moon but also provide direct and reliable evidence on the origin and evolution history of the moon. Compared with the geomorphic classification of the earth, research on lunar morphology started late and developed slowly. Although researchers have been concentrated in lunar morphology study, there is still lack of research with regards to the distribution characteristics of morphological indicators and their combination with lunar morphological classification schemes. Based on the characteristic analysis of surface elevation in lunar mare, we found that the division criteria of -2500 m and -1500 m can better distinguish the inner region of the lunar mare and the crater rim crests and highland. The study on the impact craters shows that a contour line of 3000 m can better highlight the boundary of some impact craters in the highland. Besides, the boundary of South Pole Aitken is mostly situated at an elevation of about 1000 m. Thus, four thresholds of -2500 m, -1500 m, 1000 m and 3000 m are proposed as the classification criteria in lunar morphological classification scheme, and the lunar surface is divided into five geomorphic types: extremely low altitude, low altitude, medium altitude, high altitude and extremely high altitude.