Evidence for Mg-rich carbonates on Mars from a 3.9 μm absorption feature
Evidence for Mg-rich carbonates on Mars from a 3.9 μm absorption feature
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DOI：
10.1016/j.icarus.2009.04.013
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发表时间：
2009-09-01
期刊：
影响因子：
3.2
通讯作者：
Maturilli, Alessandro
中科院分区：
文献类型：
--
作者：
Palomba, Ernesto;Zinzi, Angelo;Maturilli, Alessandro
火星早期大气的起源和性质仍存在争议。火星表面硫酸盐沉积物的发现，再加上火星风化层光学上可探测到的碳酸盐含量不高的证据，开启了不同的古气候演化路径。即使碳酸盐是TES和Mini-TES在6.76微米观察到的特征的原因，但另一种假设表明，这可能是由于水合硫酸铁(HIS)的存在。通过研究存在强泛音碳酸盐带的光谱区域，可以区分碳酸盐和HIS。自2004年1月以来，火星快车航天器上的行星傅立叶光谱仪已经获取了数千个火星光谱，范围为1.2-45微米，其中大部分在3.8至4微米之间显示出弱吸收特征。以前在地球上也观察到了类似的特征，但它的起源不能直接归因于地表物质，特别是碳酸盐。在这里，我们展示了这个带的表面性质，可以归因于碳酸盐与火星土壤物质的混合。最能再现检测到的特征的材料是富镁碳酸盐(Hunte[CaMG(3)(CO(3))(4)]和/或镁矿[MgCO(3)])。无论是在明亮的火星地区还是黑暗的火星地区，都可以看到碳酸盐的存在。对最可能丰度的评估给出了类似于10wt%的上限。碳酸盐的广泛分布支持这样一种情景，即碳酸盐的形成不是通过富水环境中的降水，而是通过风化过程。(C)2009 Elsevier Inc.保留所有权利。
The origin and nature of the early atmosphere of Mars is still debated. The discovery of sulfate deposits on the surface, coupled with the evidence that there are not large abundances of carbonates detectable on Mars in the optically accessible part of the regolith, leaves open different paleoclimatic evolutionary pathways. Even if carbonates are responsible for the feature observed by TES and Mini-TES at 6.76 mu m, alternative hypotheses suggest that it could be due to the presence of Hydrated Iron Sulfates (HIS). Carbonates can be discerned from HIS by investigating the spectral region in which a strong overtone carbonate band is present. The Planetary Fourier Spectrometer on board the Mars Express spacecraft has acquired several thousand martian spectra in the range 1.2-45 mu m since January 2004, most of which show a weak absorption feature between 3.8 and 4 mu m. A similar feature was observed previously from the Earth, but its origin could not be straightforwardly ascribed to surface materials, and specifically to carbonates. Here we show the surficial nature of this band that can be ascribed to carbonate mixed with the martian soil materials. The materials that best reproduce the detected feature are Mg-rich carbonates (huntite [CaMg(3)(CO(3))(4)] and/or magnesite [MgCO(3)]). The presence of carbonates is demonstrated in both bright and dark martian regions. An evaluation of the likeliest abundance gives an upper limit of similar to 10 wt%. The widespread distribution of carbonates supports scenarios that suggest carbonate formation occurred not by precipitation in a water-rich environment but by weathering processes. (C) 2009 Elsevier Inc. All rights reserved.