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Influence of Calcium Perchlorate on the Search for Organics on Mars with Tetramethylammonium Hydroxide Thermochemolysis
Astrobiology ( IF 4.2 ) Pub Date : 2021-03-10 , DOI: 10.1089/ast.2020.2252
Yuanyuan He 1 , Arnaud Buch 1 , Cyril Szopa 2 , Amy J Williams 3, 4 , Maëva Millan 3, 5 , Charles A Malespin 3 , Daniel P Glavin 3 , Caroline Freissinet 2 , Jennifer L Eigenbrode 3 , Samuel Teinturier 3 , David Coscia 2 , Jean-Yves Bonnet 2, 6 , Jennifer C Stern 3 , Fabien Stalport 7 , Melissa Guzman 2 , Naila Chaouche-Mechidal 7 , Pin Lu 8 , Rafael Navarro-Gonzalez 9 , Vincent Butin 1 , Jamila El Bekri 1 , Hervé Cottin 7 , Sarah Johnson 5 , Michel Cabane 2 , Paul R Mahaffy 3
Affiliation  

The Mars Organic Molecule Analyzer (MOMA) and Sample Analysis at Mars (SAM) instruments onboard the Exomars 2022 and Mars Science Laboratory rovers, respectively, are capable of organic matter detection and differentiating potentially biogenic from abiotic organics in martian samples. To identify organics, both these instruments utilize pyrolysis–gas chromatography coupled to mass spectrometry, and the thermochemolysis agent tetramethylammonium hydroxide (TMAH) is also used to increase organic volatility. However, the reactivity and efficiency of TMAH thermochemolysis are affected by the presence of calcium perchlorate on the martian surface. In this study, we determined the products of TMAH pyrolysis in the presence and absence of calcium perchlorate at different heating rates (flash pyrolysis and SAM-like ramp pyrolysis with a 35°C·min−1 heating rate). The decomposition mechanism of TMAH pyrolysis in the presence of calcium perchlorate was studied by using stepped pyrolysis. Moreover, the effect of calcium perchlorate (at Mars-relevant concentrations) on the recovery rate of fatty acids with TMAH thermochemolysis was studied. Results demonstrate that flash pyrolysis yields more diversity and greater abundances of TMAH thermochemolysis products than does the SAM-like ramp pyrolysis method. There is no obvious effect of calcium perchlorate on TMAH degradation when the [ClO4] is lower than 10 weight percent (wt %). Most importantly, the presence of calcium perchlorate does not significantly impact the recovery rate of fatty acids with TMAH thermochemolysis under laboratory conditions, which is promising for the detection of fatty acids via TMAH thermochemolysis with the SAM and MOMA instruments on Mars.

中文翻译:

高氯酸钙对四甲基氢氧化铵热化学在火星上寻找有机物的影响

火星有机分子分析仪 (MOMA) 和火星样品分析 (SAM) 仪器分别搭载在 Exomars 2022 和火星科学实验室漫游车上,能够检测有机物质并区分火星样品中的潜在生物有机物和非生物有机物。为了鉴定有机物,这两种仪器都利用热解-气相色谱与质谱联用,并且还使用热化学分解剂四甲基氢氧化铵 (TMAH) 来增加有机物的挥发性。然而,TMAH 热化学分解的反应性和效率受到火星表面高氯酸钙的影响。在本研究中,我们确定了在高氯酸钙存在和不存在下,不同加热速率(闪蒸热解和 SAM 样斜坡热解,35°C·min−1加热速率)。采用阶梯热解法研究了高氯酸钙存在下TMAH热解的分解机理。此外,研究了高氯酸钙(在火星相关浓度下)对 TMAH 热化学分解脂肪酸回收率的影响。结果表明,与类似 SAM 的斜坡热解方法相比,快速热解产生了更多多样性和更高丰度的 TMAH 热化学分解产物。当[ClO 4 ] 低于 10 重量百分比 (wt%)。最重要的是,在实验室条件下,高氯酸钙的存在不会显着影响 TMAH 热化学分解脂肪酸的回收率,这对于在火星上使用 SAM 和 MOMA 仪器通过 TMAH 热化学分解法检测脂肪酸很有希望。
更新日期:2021-03-12
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