Chang'E-4 initial spectroscopic identification of lunar far-side mantle-derived materials
Chang'E-4 initial spectroscopic identification of lunar far-side mantle-derived materials
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DOI：
10.1038/s41586-019-1189-0
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发表时间：
2019-05-16
期刊：
影响因子：
64.8
通讯作者：
Ouyang, Ziyuan
中科院分区：
文献类型：
--
作者：
Li, Chunlai;Liu, Dawei;Ouyang, Ziyuan
经过 60 多年的航天器探索，地球月球的特征是月壳 (1) 以矿物斜长石为主，上面覆盖着成分不确定的镁铁质（富含铁和镁）地幔。地壳和地幔都是在月球演化的最初阶段形成的，当时后期的吸积能量导致了熔岩（岩浆）海洋、轻斜长石的漂浮、密度较大的富铁矿物（例如橄榄石和辉石）的下沉，并最终凝固（2）。非常大的撞击坑有可能穿透地壳并采集月幔样本。其中最大的陨石坑是月球背面直径约 2,500 公里的南极艾特肯 (SPA) 盆地(3)。从轨道航天器获得的证据表明，SPA盆地的底部富含镁铁质矿物(4)，但它们的地幔起源存在争议，而且对其原位地质环境知之甚少。中国的嫦娥四号月球背面着陆器最近在冯卡门陨石坑(5,6)着陆，探索巨大的SPA盆地的底部，并部署了玉兔二号月球车。在这里，我们报告了玉兔二号上可见光和近红外光谱仪（VNIS）（7）的初步光谱观测，我们将其解释为代表了低钙（正）辉石和橄榄石的存在，这些物质可能源自月幔。地质背景(6)表明这些材料是由附近直径 72 公里的芬森撞击坑事件从 SPA 地板下方挖掘出来的，并运送到着陆点。玉兔二号的持续探索将针对冯卡门陨石坑底部的这些物质，以了解它们的地质背景、起源和丰度，并评估样本返回场景的可能性。
Over 60 years of spacecraft exploration has revealed that the Earth's Moon is characterized by a lunar crust(1) dominated by the mineral plagioclase, overlying a more mafic (richer in iron and magnesium) mantle of uncertain composition. Both crust and mantle formed during the earliest stages of lunar evolution when late-stage accretional energy caused a molten rock (magma) ocean, flotation of the light plagioclase, sinking of the denser iron-rich minerals, such as olivine and pyroxene, and eventually solidification(2). Very large impact craters can potentially penetrate through the crust and sample the lunar mantle. The largest of these craters is the approximately 2,500-kilometre-diameter South Pole-Aitken (SPA) basin(3) on the lunar far side. Evidence obtained from orbiting spacecraft shows that the floor of the SPA basin is rich in mafic minerals(4), but their mantle origin is controversial and their in situ geologic settings are poorly known. China's Chang'E-4 lunar far-side lander recently touched down in the Von Karman crater(5,6) to explore the floor of the huge SPA basin and deployed its rover, Yutu-2. Here we report on the initial spectral observations of the Visible and Near Infrared Spectrometer (VNIS)(7) onboard Yutu-2, which we interpret to represent the presence of low-calcium (ortho) pyroxene and olivine, materials that may originate from the lunar mantle. Geological context(6) suggests that these materials were excavated from below the SPA floor by the nearby 72-km-diameter Finsen impact crater event, and transported to the landing site. Continued exploration by Yutu-2 will target these materials on the floor of the Von Karman crater to understand their geologic context, origin and abundance, and to assess the possibility of sample-return scenarios.