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arXiv 2101.12450astro-ph.EP
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M3项目:2 -火星上镁铁质矿物丰度的全球分布

The M3 project: 2 -- Global distributions of mafic mineral abundances on Mars

Lucie Riu, François Poulet, Jean-Pierre Bibring, Brigitte Gondet

摘要:

一个辐射转移模型被用来再现数百万个代表火星火成岩地形的欧米茄光谱。这项任务提供了行星尺度上的模态成分和晶粒尺寸。岩性可概括为五个公里级矿物图。我们发现,火星表面的低赤道地区(从60°S到30°N)是全球主要的斜长石平均丰度约50体积%和辉石的总平均丰度接近40体积%。的LCP/(LCP+HCP)的比例的演变是观察随着时间的推移在全球范围内,这表明在整个火星时代的部分熔融程度的演变。橄榄石和火星尘埃是模拟地形的次要组成部分。橄榄石的分布与其他矿物有很大不同,因为它是在局部地区发现的,丰度达到20体积%。一种统计方法,使用k-均值聚类对丰度图的像素进行分类,突出显示了表面上七种不同的矿物组合。这一分类说明了在诺亚纪和西方纪地体中发现了不同的矿物学单元,这表明在这两个最古老的时代,在全球范围内存在着各种复杂的岩浆过程。化学成分来自模态组成图。欧米茄衍生的化学成分与以前被认为是火星表面指纹的几个独特的地球化学特征非常一致。一个主要的差异是关于铁的含量,这是显着小于土壤和岩石分析从GRS和原位测量。这种差异可以部分地由光谱建模所使用的假设来解释,或者也可以表明表面蚀变。

英文摘要:

A radiative transfer model was used to reproduce several millions of OMEGA (Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité) spectra representative of igneous terrains of Mars. This task provided the modal composition and grain sizes at a planetary scale. The lithology can be summarized in five mineral maps at km-scale. We found that the low albedo equatorial regions of the Martian surface (from 60°S to 30°N) are globally dominated by plagioclase with average abundance ~50 vol% and pyroxenes with total averaged abundance close to 40 vol%. An evolution of the LCP/(LCP+HCP) ratio is observed with time at the global scale, suggesting an evolution of the degree of partial melting throughout the Martian eras. Olivine and Martian dust are minor components of the modelled terrains. The olivine distribution is quite different from the other minerals because it is found on localized areas with abundance reaching 20 vol%. A statistical approach, to classify the pixels of the abundances maps, using k-means clustering, highlighted seven distinct mineral assemblages on the surface. This classification illustrates that diverse mineralogical units are found in the Noachian and Hesperian terrains, which suggests the presence of various and complex magmatic processes at a global scale during the two oldest eras. The chemical composition was derived from the modal composition maps. The OMEGA-derived chemical composition is quite consistent with several distinctive geochemical characteristics previously considered as fingerprints of the Martian surface. A major discrepancy is in regards to the Fe content that is significantly smaller than soil and rock analyses from GRS and in situ measurements. The discrepancy could be partly explained by the assumptions used for the spectral modelling or could also indicate surface alteration rinds.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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