Evidence of martian perchlorate, chlorate, and nitrate in Mars meteorite EETA79001: Implications for oxidants and organics
Evidence of martian perchlorate, chlorate, and nitrate in Mars meteorite EETA79001: Implications for oxidants and organics
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DOI：
10.1016/j.icarus.2013.11.012
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发表时间：
2014-02-01
期刊：
影响因子：
3.2
通讯作者：
Claire, Mark W.
中科院分区：
文献类型：
--
作者：
Kounaves, Samuel P.;Carrier, Brandi L.;Claire, Mark W.
20世纪70年代中期的维京海盗号使命的结果提供了证据，证明火星表面含有氧化剂，负责破坏有机化合物。2008年，凤凰城湿化学实验室（WCL）在三个土壤样本中发现了高氯酸盐（ClO 4-），浓度从0.5%到0.7%。维京海盗热解气相色谱-质谱仪（GC-MS）检测到氯甲烷（CH 3Cl）和二氯甲烷（CH 2Cl（2））可能是该地点的ClO 4-氧化陆地有机污染物或（如果存在）本地有机物的结果。最近，火星科学实验室（MSL）Curtain上的火星样品分析（SAM）仪器直接测量了CH 3Cl，CH 2Cl 2的存在，沿着HCl和氧气的测量，间接表明ClO-的存在。然而，除了凤凰号外，没有其他直接测量火星土壤或岩石中的ClO 4-阴离子。我们在这里报告的离子色谱（IC）和同位素分析的一个独特的木屑部分的火星陨石EETA 79001，显示存在的质量为0.6 +/- 0.1 ppm的CIOT，1.4 +/- 0.1 ppm的C10，-和16 +/- 0.2 ppm的NO;在数量和位置内的陨石是难以调和与陆地污染。锯屑样品由玄武岩材料与少量的富盐包裹体组成，其质量比为约300：1，因此盐在包裹体中的浓度可能是整个样品的300倍。NO：ClO4-; Cl-：EETA 79001的C10，-，分别为-40：1和15：1，与陨石附近的南极土壤和冰分别为-10，000：1和5000：1非常不同。此外，EETA 79001的同位素比率，δ N-15 = -10.48 +/- 0.32 ppm，δ 8180 = +51.61 +/-0.74%。与附近的米勒山脉蓝冰有很大的不同，其N-15值为+102.80 +/- 0.14 ‰，O-18值为+43.11 +/-0.64%。更重要的是，δ N-15与未受污染的Tissint火星陨石相似，815 N =-4.5%，这些发现表明，在EETA 79001中，ClO 4-，ClO 3-和NO的火星起源，并与以前的发现相结合，支持它们在火星上存在和普遍存在的假设。EETA 79001中ClO 3-的存在表明伴随存在其他高氧化性氯氧化合物，如ClO-或ClO-，由o-和y-的UV氧化和C10：4的X射线辐解产生。由于这种中间物质可能有助于有机化合物的氧化，因此只有高度难熔和/或保护良好的有机物才可能存活。ClO 4-、ClO 3-和NO2的全球存在对全球水循环、盐水的形成、人类可居住性、有机物和生命具有广泛的影响。(C)2013 Elsevier Inc. All rights reserved.
The results from the Viking mission in the mid 1970s provided evidence that the martian surface contained oxidants responsible for destroying organic compounds. In 2008 the Phoenix Wet Chemistry Lab (WCL) found perchlorate (ClO4-) in three soil samples at concentrations from 0.5 to 0.7 wt%. The detection of chloromethane (CH3Cl) and dichloromethane (CH2Cl(2)) by the Viking pyrolysis gas chromatograph-mass spectrometer (GC-MS) may have been a result of ClO4- at that site oxidizing either terrestrial organic contaminates or, if present, indigenous organics. Recently, the Sample Analysis at Mars (SAM) instrument on the Mars Science Laboratory (MSL) Curiosity directly measured the presence of CH3Cl, CH2Cl2 and, along with measurements of HCl and oxygen, indirectly indicate the presence of ClO-. However, except for Phoenix, no other direct measurement of the ClO4- anion in martian soil or rock has been made. We report here ion chromatographic (IC) and isotopic analyses of a unique sawdust portion of the martian meteorite EETA79001 that show the presence by mass of 0.6 +/- 0.1 ppm CIOT,, 1.4 +/- 0.1 ppm C10,-, and 16 +/- 0.2 ppm NO; at a quantity and location within the meteorite that is difficult to reconcile with terrestrial contamination. The sawdust sample consists of basaltic material with a minor salt-rich inclusion in a mass ratio of -300:1, thus the salts may be 300 times more concentrated within the inclusion than the whole sample. The molar ratios of NO : ClO4-; and Cl- : C10,-, are very different for EETA79001 at -40:1 and 15:1, respectively, than the Antarctic soils and ice near where the meteorite was recovered at -10,000:1 and 5000:1, respectively. In addition, the isotope ratios for EETA79001 with delta N-15 = -10.48 +/- 0.32 parts per thousand and 8180 = +51.61 +/- 0.74%. are significantly different from that of the nearby Miller Range blue ice with delta N-15 = +102.80 +/- 0.14 parts per thousand and delta O-18 = +43.11 +/- 0.64%, This difference is notable, because if the meteorite had been contaminated with nitrate from the blue ice, the delta N-15 values should be the same. More importantly, the delta N-15 is similar to the uncontaminated Tissint Mars meteorite with 815N = -4.5%, These findings suggest a martian origin of the ClO4-, ClO3- and NO; in EETA79001, and in conjunction with previous discoveries, support the hypothesis that they are present and ubiquitous on Mars. The presence of ClO3- in EETA79001 suggests the accompanying presence of other highly oxidizing oxychlorines such as ClO- or ClO-, produced both by UV oxidation of o- and y- and X-ray radiolysis of C10:4. Since such intermediary species may contribute to oxidization of organic compounds, only highly refractory and/or well-protected organics are likely to survive. The global presence of ClO4-, ClO3-, and NO;, has broad implications for the planet-wide water cycle, formation of brines, human habitability, organics, and life. (C) 2013 Elsevier Inc. All rights reserved.