月球小型撞击坑形貌特征及退化规律研究

发布时间：2018-08-11 20:45

【摘要】：月球是地月系乃至太阳系空间陨石撞击记录的样板星球,撞击坑是其最明显的形貌特征,它对我们研究月球演化、太阳系陨石撞击历史和空间环境等都有重要的意义。从上个世纪90年代起,以开发利用月球资源为目标,国际上掀起了新一轮的月球探测高潮。开展月球探测工作是我国迈出航天深空探测第一步的重大举措。我国的嫦娥卫星,尤其是“嫦娥二号”,针对月球形貌的研究获取了大量高精度的月球表面影像数据,为月球形貌特征和撞击坑形态规律的精细研究提供了充足的数据支持。本文以嫦娥工程的科学研究和应用为背景,利用嫦娥二号获取的大量高精度遥感数据,以虹湾为研究区,从月球小型撞击坑的形态特征和统计特征入手,对撞击坑退化规律,以及地质单位的撞击年龄、撞击时序规律等问题进行研究。首先,本文系统介绍了小型撞击坑构造的形貌特征和演化特征。月球上的小型撞击坑多为碗形的简单撞击坑,直径一般小于15～20千米,分布广泛,数量众多,而且受到退化影响规律更明显,是利用统计方法进行撞击坑形态特征和演化规律研究的较理想对象。其次,对大量数据的分析,撞击坑自动识别方法和形态参数自动提取方法的研究非常必要。本文尝试性的应用基于影像数据的区域分割的方法、基于地形数据的等值线特征约束的方法,进行撞击坑的自动识别；应用坡度分割方法从地形数据中进行了撞击坑形态参数的自动提取。本文分析了研究区撞击坑形态参数的分布特征和相关性,并选用撞击坑深度作为退化特征的标志参数。然后,本文通过撞击坑大小频率统计和形态参数统计两种方法研究退化规律。撞击坑的退化是指撞击坑在微小陨石撞击等空间环境影响下逐渐暗淡、填充甚至消失的现象。通过大小频率分布,退化的统计特征通常表现为均衡现象,均衡的演化可以表示地质单元相对年龄的变化；撞击坑的形态特征即退化状态可以直接表征撞击坑形成年龄,进而反应地质单元的形成年代,退化参数是地质单元相对年代的标志性参数。针对利用小型撞击坑进行撞击年龄计算的问题,综合考虑了撞击坑退化因素、次级撞击坑影响和计算精度等问题,提出了一个较谨慎的解决方法。该方法通过撞击坑大小频率分析得出用来计算撞击年龄的撞击坑尺度范围,即避开受退化影响的分布区和次级撞击坑的密集分布区,同时撞击坑标绘中利用形态特征排除次级坑,由此可以取得较可靠的计算结果。本文分析了计算模型的不确定性,以及统计过程对结果的影响。针对撞击时序规律的研究,本文以形态演化特征及退化状态为入手点,以撞击坑深度变化作为退化的标识参数,模拟不同时间下撞击坑族的大小频率分布特征,并得出基于撞击坑大小深度的时序特征线,进而得到退化模型。通过退化模型,可以估计小型撞击坑的撞击年代和退化过程,从而模拟出不同年代的撞击坑分布。本文以小型撞击坑的形貌特征和演化研究为基础,选择典型月海地质单元为研究区域,系统研究撞击坑的形貌特征和退化规律,建立了定量的退化过程模型,并针对撞击年龄的计算问题、撞击时序等问题进行了探讨。本文的研究内容对研究陨石撞击的分布特征和空间环境的变化等具有重要意义。
[Abstract]:The Moon is a model planet recorded by meteorite impacts in the Earth-Moon system and even in the solar system. The impact crater is the most obvious feature of its morphology. It is of great significance to the study of the evolution of the Moon, the history of meteorite impacts in the solar system and the space environment. Since the 1990s, with the aim of exploiting and utilizing the lunar resources, a new international trend has been set off. Lunar exploration is the climax of lunar exploration. The lunar exploration is the first step of space exploration in China. China's Chang'e satellite, especially the Chang'e-2 satellite, has obtained a large number of high-precision image data of the lunar surface for the study of lunar morphology characteristics and impact crater morphology. Sufficient data support is provided.
Based on the scientific research and application of Chang'e project, this paper studies the degradation law of impact craters, the impact age of geological units, and the impact time series law of small impact craters on the moon in Hongwan research area by using a large number of high-precision remote sensing data obtained by Chang'e 2.
Firstly, the morphological and evolutionary characteristics of the small impact craters are systematically introduced. Most of the small impact craters on the moon are bowl-shaped, simple impact craters with a diameter of less than 15-20 km. They are widely distributed, numerous in number, and more obviously affected by degradation. They are the morphological and evolutionary characteristics of impact craters by statistical methods. The ideal object of the study.
Secondly, it is necessary to study the methods of automatic identification of impact craters and automatic extraction of morphological parameters for the analysis of a large number of data. In this paper, the distribution characteristics and correlation of the shape parameters of the impact crater in the study area are analyzed, and the depth of the impact crater is selected as a marker parameter of the degradation characteristics.
The degradation of impact craters is defined as the gradual fading, filling and even disappearance of impact craters under the influence of space environment such as micro meteorite impacts. Evolution can indicate the change of relative age of geological unit, and the morphological characteristics of impact crater, i.e. the degeneration state, can directly indicate the age of formation of impact crater and then reflect the age of formation of geological unit.
In order to solve the problem of calculating the impact age of a small impact crater, a more cautious method is proposed, which considers the deterioration factor of the impact crater, the influence of the secondary impact crater and the calculation accuracy. In this paper, the uncertainty of the calculation model and the influence of the statistical process on the results are analyzed.
Aiming at the study of impact time series, this paper takes the morphological evolution and degeneration as the starting point, and takes the change of crater depth as the degeneration index parameter, simulates the size and frequency distribution characteristics of the impact crater family at different time, and obtains the time series characteristic line based on the size and depth of the impact crater, and then obtains the degeneration model. It can estimate the impact age and degradation process of small impact craters and simulate the distribution of impact craters in different ages.
Based on the study of the morphological characteristics and evolution of small impact craters, a typical lunar sea geological unit is selected as the study area. The morphological characteristics and Degradation Laws of impact craters are systematically studied. A quantitative degradation process model is established. The calculation of impact age and impact time series are discussed. It is of great significance to study the distribution characteristics of meteorite impact and the change of space environment.
【学位授予单位】：武汉大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：P184

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