基于撞击坑自动识别的月球雨海北部地区(LQ-4)月海玄武岩定年研究

Research on dating of the mare basalts based on the automatic identification of impact craters in the northern region of Mare Imbrium on the Moon(LQ-4)

月球表面定年研究对于理解和重建月球地质演化历史具有关键作用,撞击坑尺寸-频率分布法(CS-FD)是通过统计区域内不同尺寸撞击坑密度得到特定地质单元的绝对地质年龄。雨海北部地区(LQ-4)包括雨海北部、冷海西部地区以及风暴洋东北部等月海,位于雨海西北边缘的虹湾是中国嫦娥三号卫星预选软着落区,文中综合使用3种方法从影像和地形数据中自动提取了该区内的撞击坑。利用Clementine光谱数据对雨海北部和风暴洋东北部内玄武岩进行了分区,利用撞击坑尺寸-频度法(CSFD)法得到每个玄武岩分区内的定年结果。对比该地区之前的定年数据后发现,使用自动识别结果得到的各分区定年结果新老整体趋势上与之前研究结果基本一致,但存在一定偏差。根据自动识别定年结果,认为该地区玄武岩新老顺序大致为:雨海东部(3.56Ga)—虹湾(3.38Ga)—风暴洋东北部(2.74Ga)—雨海西部(2.63Ga)—柏拉图坑(2.37Ga)。结合撞击坑自动识别技术和CSFD法,形成了一条利用影像和地形遥感数据快速得到月球表面地质年龄的方法,为月球年代学研究提供一种新途径。

Dating of the lunar surface plays a key role in understanding and reconstruction of lunar geological evolution,and crater sizefrequency distribution method（CSFD） could get the absolute geological age of a specific geological unit according to crater density of different sizes in the region.The northern region of Mare Imbrium（LQ-4） consists of the northern part of Mare Imbrium,the western region of Mare Frigoris and the northeastern Oceanus Procellarum;Sinus Iridum located at the northwestern edge of the Mare Imbrium is the China＇s Chang＇e III satellite preselected soft landing area.This paper extracted the impact craters automatically from the images and terrain data in the area of impact craters with three methods.Basalt of the northern part of Mare Imbrium and in the northeastern Oceanus Procellarum was partitioned by Clementine spectral data,and dating results of each basalt region were obtained by using CSFD.We found that there is a certain deviation in the dating results obtained by means of automatic identification comparing with previous dating data in the region,but for each partition the new and old overall trend is basically consistent with the previous research results.The automatic identification dating results show that for the basalt areas,the geochronolgy roughly is as follows： eastern Mare Imbrium（3.56 Ga）Sinus Iridium（3.38 Ga）northeastern Oceanus Procellarum（2.74 Ga）western Mare Imbrium（2.63 Ga）Crater Plato（2.37 Ga）.With the combination of automatic identification of impact cracters,this paper basically provided a technical approach which can quickly get the lunar surface geological age with remote sensing data,and the new approach provides a new way for the lunar chronology.