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Formation of Methane and (Per)Chlorates on Mars
ACS Earth and Space Chemistry ( IF 2.9 ) Pub Date : 2018-12-17 00:00:00 , DOI: 10.1021/acsearthspacechem.8b00104
Svatopluk Civiš 1 , Antonín Knížek 1, 2 , Paul B. Rimmer 3, 4, 5 , Martin Ferus 1 , Petr Kubelík 1, 6 , Markéta Zukalová 1 , Ladislav Kavan 1 , Elias Chatzitheodoridis 7
Affiliation  

Methane, perchlorates, chlorates, and methyl chlorides have all been detected on Mars. The origin of these species has never been adequately explained. In this paper, we irradiated mixtures of CO2, HCl, and a mineral catalyst—anatase, rutile, montmorillonite, and the Nakhla meteorite—with soft UV radiation for up to 3500 h and observed the formation of perchlorates, chlorates, methyl chlorides, and methane in a single experiment. Additionally, the methanogenesis for anatase was observed at −196 °C. Further, we propose that while methane is decomposed relatively quickly and therefore attains a steady-state concentration (0.41 ± 0.16 ppbv), the chlorinated compounds are much more stable and therefore would have accumulated throughout the Martian history. We estimate that this mechanism would be sufficient in the course of Martian history to accumulate perchlorate in the soil in 0.5 wt % in 5–50 cm depth, which is in accordance with the observed perchlorate content on Mars. This predicted perchlorate gradient may be observed with the Insight rover. Further, if microbes are present on Mars, they will likely inhabit depths below the perchlorate (i.e., 5–50 cm). This chemistry likely still continues on Mars to a certain extent, and any future exploration by rovers or planetary models should account for this process during their analyses.

中文翻译:

火星上甲烷和(全)氯的形成

在火星上都检测到了甲烷,高氯酸盐,氯酸盐和甲基氯。这些物种的起源尚未得到充分的解释。在本文中,我们辐照了CO 2的混合物,HCl和矿物催化剂(锐钛矿,金红石,蒙脱石和Nakhla陨石)在长达3500 h的紫外线下进行柔和的紫外线照射,并在单个实验中观察到了高氯酸盐,氯酸盐,甲基氯和甲烷的形成。另外,在-196℃下观察到锐钛矿的甲烷生成。此外,我们提出,尽管甲烷分解相对较快,因此达到了稳态浓度(0.41±0.16 ppbv),但氯化物更加稳定,因此将在整个火星历史中积累。我们估计,在火星历史过程中,这种机制足以在土壤中5-5 cm深度以0.5 wt%的浓度积聚高氯酸盐,这与在火星上观察到的高氯酸盐含量是一致的。Insight流动站可能会观测到该预测的高氯酸盐梯度。此外,如果火星上存在微生物,则它们很可能栖息在高氯酸盐以下的深度(即5–50厘米)。这种化学现象很可能仍会在火星上继续延续到一定程度,未来任何由漫游者或行星模型进行的探索都应在分析过程中说明这一过程。
更新日期:2018-12-17
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