嫦娥五号样品——月球遥感定量反演的新地面真值

Chang’E-5 samples——New“ground truth”for the quantitative inversion of lunar remote sensing

嫦娥五号任务从月球风暴洋东北部成功返回了1731 g月壤样品.最新返回的月壤有望为月球遥感数据定量反演提供新的地面真值(Ground Truth).本研究中首先利用遥感数据获取了着陆单元的矿物组成和化学成分(FeO,TiO2,Th),并与嫦娥五号月壤样品实验室分析结果进行对比.二者之间的差异(特别是橄榄石含量)反映了目前利用遥感数据反演元素和矿物含量的方法仍存在提升空间.本研究通过系统地对比分析发现:(1)嫦娥五号月壤具有高铁、中钛、富钍的化学特征,显著区别于已有阿波罗月壤,可为月球遥感研究提供全新的地面真值;(2)嫦娥五号月壤代表了一类发育成熟的年轻月海月壤,外来溅射物占比较小,能够反映着陆区玄武岩的成分特征;(3)嫦娥五号月壤粒径较小,符合Lunar Soil Characterization Consortium(LSCC)提供地面真值的样品标准(<45μm).此外,嫦娥五号着陆区也具有独特性:(1)位于月球正面西部的中纬度地区,不同于美苏样品返回任务所着陆的低纬度区域;(2)位于月球晚期玄武岩单元,区别于已有的光谱定标区.因此,以嫦娥五号月壤实测数据为地面真值,进而将嫦娥五号着陆区构建为全新的遥感定标点,可以显著扩大定标点的地理范围和全球代表性.基于着陆区遥感及样品研究成果,本研究在嫦娥五号着陆区所在单元(Em4)内划定了定标区的范围,可为后续遥感定标区的建立提供参考.

The Chang’E-5(CE-5)mission successfully returned 1731 g of lunar soil samples from the northeast of the Oceanus Procellarum.The newly returned lunar soil can provide a new ground truth for the quantitative inversion of lunar remote sensing data.In this study,the mineral and chemical compositions(FeO,TiO2,Th)of the landing region were obtained from the remote sensing data and compared with the laboratory analysis results of the CE-5 lunar soil samples.The differences between them(especially the olivine content)indicate that there is still room for improvement in the methods for retrieving the elemental and mineral abundances using remote sensing data.Through a systematic comparative analysis,we discovered that:(1)the geochemical characteristics of high FeO,medium TiO2,and abundant Th in the CE-5lunar soil are significantly different from the existing Apollo lunar soil,which can provide unique ground truth for remote sensing research;(2)The CE-5 lunar soil represents mature lunar soil developed on the young basalt unit on the moon,with a small proportion of distantly sourced ejecta,representing the mare basalt composition characteristics of the landing region;(3)The CE-5 lunar soil is very fine,which meets the sample standard(<45μm)of the Lunar Soil Characterization Consortium for providing ground truth.Notably,the CE-5 landing region also exhibits unique characteristics:(1)it is located in the mid-latitude region on the western hemisphere of the moon,different from the lowlatitude region where the United States and the Soviet Union sample return missions landed;(2)it is located on the latestage lunar basalt unit;it is different from the existing spectral calibration area.Therefore,the construction of the CE-5landing area as a new remote sensing calibration site based on the measured data of its lunar soil can significantly expand the geographical scope and global representation of the lunar calibration sites.Based on the results of the remote sensing and sample studies,we delineate the calibration area in the unit where the CE-5 landing site is located(Em4),thus providing a reference for establishing a remote sensing calibration area in the future.