Constraints on abundance, composition, and nature of X-ray amorphous components of soils and rocks at Gale crater, Mars
Constraints on abundance, composition, and nature of X-ray amorphous components of soils and rocks at Gale crater, Mars
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DOI：
10.1002/2014je004716
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发表时间：
2014-12-01
影响因子：
4.8
通讯作者：
Cousin, Agnes
中科院分区：
文献类型：
--
作者：
Dehouck, Erwin;McLennan, Scott M.;Cousin, Agnes
在火星科学实验室任务的第一年，好奇号的化学和矿物学 (CheMin) 仪器分析了三个样品的 X 射线衍射图：Rocknest 砂、John Klein 和 Cumberland 钻屑（均从 Sheepbed 泥岩中提取）显示出存在来源不明的重要非晶态成分的证据。我们开发了一个质量平衡计算程序，可以在 CheMin 数据得出的矿物丰度的不确定性范围内确定这些样品的结晶和非晶成分的可能化学成分范围。反过来，化学成分限制了实际成分所需的无定形组分的最小丰度（所有氧化物均为 0wt%）：Rocknest 为 21-22wt%，Cumberland 为 15-20wt%，与衍射图样得出的估计值（分别为 27 和 31wt%）非常吻合。尽管 Rocknest 砂和 Sheepbed 泥岩之间存在明显差异，但这两个地点的非晶态成分在化学上非常相似，具有相当浓度的 SiO2、TiO2、Al2O3、Cr2O3、FeOT、CaO、Na2O、K2O 和 P2O5。 Rocknest 中的 MgO 往往较低，但根据 Sheepbed 中蒙皂石的确切成分，两个样品之间的 MgO 也可能具有可比性。唯一明确的区别是 SO3 含量，Rocknest 中的 SO3 含量始终较高。观察到的相似性表明这两种无定形成分具有共同的起源或形成过程。无定形组分中可能存在的各个相包括：火山（或冲击）玻璃、硅石（或二氧化硅+水铁矿）、无定形硫酸盐（或吸附的SO42-）和纳米相氧化铁。
X-ray diffraction patterns of the three samples analyzed by Curiosity's Chemistry and Mineralogy (CheMin) instrument during the first year of the Mars Science Laboratory missionthe Rocknest sand, and the John Klein and Cumberland drill fines, both extracted from the Sheepbed mudstoneshow evidence for a significant amorphous component of unclear origin. We developed a mass balance calculation program that determines the range of possible chemical compositions of the crystalline and amorphous components of these samples within the uncertainties of mineral abundances derived from CheMin data. In turn, the chemistry constrains the minimum abundance of amorphous component required to have realistic compositions (all oxides 0wt %): 21-22wt % for Rocknest and 15-20wt % for Cumberland, in good agreement with estimates derived from the diffraction patterns (27 and 31wt %, respectively). Despite obvious differences between the Rocknest sand and the Sheepbed mudstone, the amorphous components of the two sites are chemically very similar, having comparable concentrations of SiO2, TiO2, Al2O3, Cr2O3, FeOT, CaO, Na2O, K2O, and P2O5. MgO tends to be lower in Rocknest, although it may also be comparable between the two samples depending on the exact composition of the smectite in Sheepbed. The only unambiguous difference is the SO3 content, which is always higher in Rocknest. The observed similarity suggests that the two amorphous components share a common origin or formation process. The individual phases possibly present within the amorphous components include: volcanic (or impact) glass, hisingerite (or silica+ferrihydrite), amorphous sulfates (or adsorbed SO42-), and nanophase ferric oxides.