Perchlorate‐induced combustion of organic matter with variable molecular weights: Implications for Mars missions

Sephton, Mark A.; Lewis, J. M. T.; Watson, Jonathan S.; Montgomery, W J; Garnier, Carole

doi:10.1002/2014gl062109

Cited by 18 publications

(14 citation statements)

References 23 publications

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“…A well‐known example for Mars comes from the presence of perchlorate salts in the soil, which are thermally decomposed to release molecular oxygen and chlorine‐bearing volatile compounds such as HCl. These species lead to the oxidation and chlorination of organics during the pyrolysis [ Glavin et al , ; Ming et al , ; Navarro‐Gonzalez et al , ; Steininger et al , ; Sephton et al , ]. The perchlorates were first detected in northern Martian soils during the Phoenix mission [ Hecht et al , ], and more recently in Gale Crater by SAM [ Glavin et al , ; Leshin et al , ; Ming et al , ].…”

Section: Introductionmentioning

confidence: 99%

Magnesium sulfate as a key mineral for the detection of organic molecules on Mars using pyrolysis

et al. 2016

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International audiencePyrolysis of soil or rock samples is the preferred preparation technique used on Mars to search for organic molecules up today. During pyrolysis, oxichlorines present in the soil of Mars release oxidant species that alter the organic molecules potentially contained in the samples collected by the space probes. This process can explain the difficulty experienced by in situ exploration probes to detect organic materials in Mars soil samples until recently. Within a few months, the Curiosity rover should reach and analyze for the first time soils rich in sulfates which could induce a different behavior of the organics during the pyrolysis compared with the types of soils analyzed up today. For this reason, we systematically studied the pyrolysis of organic molecules trapped in magnesium sulfate, in the presence or absence of calcium perchlorate. Our results show that organics trapped in magnesium sulfate can undergo some oxidation and sulfuration during the pyrolysis. But these sulfates are also shown to protect organics trapped inside the crystal lattice and/or present in fluid inclusions from the oxidation induced by the decomposition of calcium perchlorate, and probably other oxychlorine phases currently detected on Mars. Trapped organics may also be protected from degradation processes induced by other minerals present in the sample, at least until these organics are released from the pyrolyzed sulfate mineral (~700 °C in our experiment). Hence, we suggest magnesium sulfate as one of the minerals to target in priority for the search of organic molecules by the Curiosity and ExoMars 2018 rovers

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Section: Introductionmentioning

confidence: 99%

Magnesium sulfate as a key mineral for the detection of organic molecules on Mars using pyrolysis

et al. 2016

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“…Decomposition of Mg-perchlorate leads to formation of MgO and MgCl 2 as well as O 2 and Cl 2 , or their associated radicals (Manelis et al, 2003;Navarro-González et al, 2010Steininger et al, 2012). O and Cl radicals further lead to the formation of CO 2 from organic matter and chlorinated organic compounds via oxidation and chlorination, respectively (Sephton et al, 2014). A determination of exact parent molecules of chlorinated compounds observed in our study is difficult, if not impossible.…”

Section: Applicability Of Different Techniques and Impact Of Perchloratementioning

confidence: 71%

“…Perchlorates are relatively inactive at low temperatures (i.e., martian surface temperatures) and thus, for example, remain unreacted in soils (Brown and Gu, 2006;Catling et al, 2010). However, they become reactive during heating, as the perchlorate molecule decomposes in the temperature range of 200-600°C, forming products likely leading to oxidation and chlorination of organic compounds (Navarro-González et al, 2010Steininger et al, 2012;Sephton et al, 2014). Potential biosignatures may therefore be destroyed in the presence of perchlorates, either by chemical alteration or complete combustion (i.e., transformation into CO 2 ; Steininger et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Investigating the Effect of Perchlorate on Flight-like Gas Chromatography–Mass Spectrometry as Performed by MOMA on board the ExoMars 2020 Rover

et al. 2019

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The Mars Organic Molecule Analyzer (MOMA) instrument on board ESA's ExoMars 2020 rover will be essential in the search for organic matter. MOMA applies gas chromatography-mass spectrometry (GC-MS) techniques that rely on thermal volatilization. Problematically, perchlorates and chlorates in martian soils and rocks become highly reactive during heating (>200°C) and can lead to oxidation and chlorination of organic compounds, potentially rendering them unidentifiable. Here, we analyzed a synthetic sample (alkanols and alkanoic acids on silica gel) and a Silurian chert with and without Mg-perchlorate to evaluate the applicability of MOMA-like GC-MS techniques to different sample types and assess the impact of perchlorate. We used a MOMA flight analog system coupled to a commercial GC-MS to perform MOMA-like pyrolysis, in situ derivatization, and in situ thermochemolysis. We show that pyrolysis can provide a sufficient overview of the organic inventory but is strongly affected by the presence of perchlorates. In situ derivatization facilitates the identification of functionalized organics but showed low efficiency for n-alkanoic acids. Thermochemolysis is shown to be an effective technique for the identification of both refractory and functional compounds. Most importantly, this technique was barely affected by perchlorates. Therefore, MOMA GC-MS analyses of martian surface/subsurface material may be less affected by perchlorates than commonly thought, in particular when applying the full range of available MOMA GC-MS techniques.

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“…Even for minerals that induce complete combustion of any organic matter present, the amount and temperature of release for carbon dioxide provide information relevant to the search for organic matter (Sephton et al , 2014). Carbon dioxide is readily detectable by FTIR and can be recognized at a few parts per million or less for pyrolysis-FTIR.…”

Section: Discussionmentioning

confidence: 99%

Organic Matter Detection on Mars by Pyrolysis-FTIR: An Analysis of Sensitivity and Mineral Matrix Effects

Gordon

Sephton

2016

Astrobiology

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Returning samples from Mars will require an effective method to assess and select the highest-priority geological materials. The ideal instrument for sample triage would be simple in operation, limited in its demand for resources, and rich in produced diagnostic information. Pyrolysis–Fourier infrared spectroscopy (pyrolysis-FTIR) is a potentially attractive triage instrument that considers both the past habitability of the sample depositional environment and the presence of organic matter that may reflect actual habitation. An important consideration for triage protocols is the sensitivity of the instrumental method. Experimental data indicate pyrolysis-FTIR sensitivities for organic matter at the tens of parts per million level. The mineral matrix in which the organic matter is hosted also has an influence on organic detection. To provide an insight into matrix effects, we mixed well-characterized organic matter with a variety of dry minerals, to represent the various inorganic matrices of Mars samples, prior to analysis. During pyrolysis-FTIR, serpentinites analogous to those on Mars indicative of the Phyllocian Era led to no negative effects on organic matter detection; sulfates analogous to those of the Theiikian Era led, in some instances, to the combustion of organic matter; and palagonites, which may represent samples from the Siderikian Era, led, in some instances, to the chlorination of organic matter. Any negative consequences brought about by these mineral effects can be mitigated by the correct choice of thermal extraction temperature. Our results offer an improved understanding of how pyrolysis-FTIR can perform during sample triage on Mars. Key Words: Mars—Life-detection instruments—Search for Mars’ organics—Biosignatures. Astrobiology 16, 831–845.

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Perchlorate‐induced combustion of organic matter with variable molecular weights: Implications for Mars missions

Cited by 18 publications

References 23 publications

Magnesium sulfate as a key mineral for the detection of organic molecules on Mars using pyrolysis

Magnesium sulfate as a key mineral for the detection of organic molecules on Mars using pyrolysis

Investigating the Effect of Perchlorate on Flight-like Gas Chromatography–Mass Spectrometry as Performed by MOMA on board the ExoMars 2020 Rover

Organic Matter Detection on Mars by Pyrolysis-FTIR: An Analysis of Sensitivity and Mineral Matrix Effects

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