Fresh emplacement of hydrated sodium chloride on Ceres from ascending salty fluids
Fresh emplacement of hydrated sodium chloride on Ceres from ascending salty fluids
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DOI：
10.1038/s41550-020-1138-8
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发表时间：
2020-08-01
期刊：
影响因子：
14.1
通讯作者：
Russell, C. T.
中科院分区：
文献类型：
--
作者：
De Sanctis, M. C.;Ammannito, E.;Russell, C. T.
从黎明获得的高空间分辨率光谱数据检测到谷神星上的谷类光斑存在新鲜的氯盐。这些盐的水化程度的空间分布表明，它们最早在几个世纪前浮出水面，含盐流体的上升流可能仍然活跃。谷神星的表面和内部结构显示出全球水蚀变过程的证据，表明过去存在海洋。然而，目前还不清楚这片海洋的一部分是否仍然存在，以及残存的流体是否仍在这颗矮行星上循环。这些流体可能暴露在地质上年轻的表面，而最有希望证实谷神星上存在现代流体的地点是位于Occator陨石坑的谷类光斑穹顶。这个非常年轻的光斑展示了在我们的太阳系中相对罕见的矿物，它的形成需要液态水的存在和热液活动的结合。在这里，我们报告了水合氯化钠在谷类光斑上的发现。这些新发现的氯盐集中在穹顶的顶部，靠近放射状裂缝系统。水化相的空间分布表明，氯盐是最近才到达地表或仍在上升的深层卤水的固体残留物。这些盐在维持谷神星温暖的内部温度和降低卤水的共晶温度方面非常有效，在这种情况下，今天的谷神星中可能存在上升的含盐流体。
Spectroscopic data obtained at high spatial resolution from Dawn detected the presence of fresh chloride salts at Cerealia Facula on Ceres. The spatial distribution of the hydration level of these salts suggests that they surfaced a maximum of a few centuries ago and that the upwelling of salty fluids may still be active.The surface and internal structure of Ceres show evidence of a global process of aqueous alteration, indicating the existence of an ocean in the past. However, it is not clear whether part of this ocean is still present and whether residual fluids are still circulating in the dwarf planet. These fluids may be exposed in a geologically young surface, and the most promising site to verify the occurrence of present fluids on Ceres is Cerealia Facula dome, in Occator crater. This very young facula exhibits minerals that are relatively rare in our Solar System, the formation of which requires the presence of liquid water in combination with hydrothermal activity. Here we report the discovery of hydrated sodium chloride on Cerealia Facula. These newly identified chloride salts are concentrated on the top of the dome, close to a system of radial fractures. The spatial distribution of the hydrated phase suggests that chloride salts are the solid residue of deep brines that reached the surface only recently, or are still ascending. These salts are very efficient in maintaining Ceres's warm internal temperature and lowering the eutectic temperature of the brines, in which case ascending salty fluids may exist in Ceres today.