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Chloromethane release from carbonaceous meteorite affords new insight into Mars lander findings.

Keppler F, Harper DB, Greule M, Ott U, Sattler T, Schöler HF, Hamilton JT - Sci Rep (2014)

Bottom Line: Controversy continues as to whether chloromethane (CH3Cl) detected during pyrolysis of Martian soils by the Viking and Curiosity Mars landers is indicative of organic matter indigenous to Mars.Thus CH3Cl emissions recorded by Mars lander experiments may be attributed to methoxyl groups in undegraded organic matter in meteoritic debris reaching the Martian surface being converted to CH3Cl with perchlorate or chloride in Martian soil.However we cannot discount emissions arising additionally from organic matter of indigenous origin.

View Article: PubMed Central - PubMed

Affiliation: 1] Institute of Earth Sciences, University of Heidelberg, Im Neuenheimer Feld 234-236, 69120 Heidelberg, Germany [2] Max-Planck-Institute for Chemistry, Hahn-Meitner-Weg 1, 55128 Mainz, Germany.

ABSTRACT
Controversy continues as to whether chloromethane (CH3Cl) detected during pyrolysis of Martian soils by the Viking and Curiosity Mars landers is indicative of organic matter indigenous to Mars. Here we demonstrate CH3Cl release (up to 8 μg/g) during low temperature (150-400°C) pyrolysis of the carbonaceous chondrite Murchison with chloride or perchlorate as chlorine source and confirm unequivocally by stable isotope analysis the extraterrestrial origin of the methyl group (δ(2)H +800 to +1100‰, δ(13)C -19.2 to +10‰,). In the terrestrial environment CH3Cl released during pyrolysis of organic matter derives from the methoxyl pool. The methoxyl pool in Murchison is consistent both in magnitude (0.044%) and isotope signature (δ(2)H +1054 ± 626‰, δ(13)C +43.2 ± 38.8‰,) with that of the CH3Cl released on pyrolysis. Thus CH3Cl emissions recorded by Mars lander experiments may be attributed to methoxyl groups in undegraded organic matter in meteoritic debris reaching the Martian surface being converted to CH3Cl with perchlorate or chloride in Martian soil. However we cannot discount emissions arising additionally from organic matter of indigenous origin. The stable isotope signatures of CH3Cl detected on Mars could potentially be utilized to determine its origin by distinguishing between terrestrial contamination, meteoritic infall and indigenous Martian sources.

No MeSH data available.


Related in: MedlinePlus

Isotopic composition of CH3Cl of terrestrial and extraterrestrial organic matter.Stable carbon and hydrogen isotope composition of CH3Cl released during low temperature pyrolysis of terrestrial and extraterrestrial organic matter. The green box indicates hypothetical biological Martian signatures based on assumptions provided in the discussion section, the most important of which is that we assumed that life forms on Mars would have evolved in a similar way to those on earth.
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f6: Isotopic composition of CH3Cl of terrestrial and extraterrestrial organic matter.Stable carbon and hydrogen isotope composition of CH3Cl released during low temperature pyrolysis of terrestrial and extraterrestrial organic matter. The green box indicates hypothetical biological Martian signatures based on assumptions provided in the discussion section, the most important of which is that we assumed that life forms on Mars would have evolved in a similar way to those on earth.

Mentions: The mean δ13C value for the terrestrial methoxyl pool (−49.2 ± 1.2‰) was quite different from that for Murchison (+43.2 ± 38.8). The organic carbon in Murchison has been reported to be isotopically very heterogeneous24 and this might explain the much larger variations for δ13C values found for the methoxyl groups of Murchison. Similarly, mean δ13C values of CH3Cl emissions from terrestrial soil (ranging from −74 to −54‰) and Murchison (ranging from −19.2 to +10‰) on pyrolysis between 200 and 350°C were distinct from one another, (Fig. 5, Supplementary Table 1). Figure 6 shows a two-dimensional plot of the δ13C and δ2H values of CH3Cl emissions from the terrestrial environment and Murchison. Also shown are the predicted values for CH3Cl emissions from a biological Martian origin (for details of assumptions made see discussion). From this figure it is clear that isotopic signatures would be a powerful tool in constraining the origin of the organic matter precursor of CH3Cl derived from Martian soil.


Chloromethane release from carbonaceous meteorite affords new insight into Mars lander findings.

Keppler F, Harper DB, Greule M, Ott U, Sattler T, Schöler HF, Hamilton JT - Sci Rep (2014)

Isotopic composition of CH3Cl of terrestrial and extraterrestrial organic matter.Stable carbon and hydrogen isotope composition of CH3Cl released during low temperature pyrolysis of terrestrial and extraterrestrial organic matter. The green box indicates hypothetical biological Martian signatures based on assumptions provided in the discussion section, the most important of which is that we assumed that life forms on Mars would have evolved in a similar way to those on earth.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4230006&req=5

f6: Isotopic composition of CH3Cl of terrestrial and extraterrestrial organic matter.Stable carbon and hydrogen isotope composition of CH3Cl released during low temperature pyrolysis of terrestrial and extraterrestrial organic matter. The green box indicates hypothetical biological Martian signatures based on assumptions provided in the discussion section, the most important of which is that we assumed that life forms on Mars would have evolved in a similar way to those on earth.
Mentions: The mean δ13C value for the terrestrial methoxyl pool (−49.2 ± 1.2‰) was quite different from that for Murchison (+43.2 ± 38.8). The organic carbon in Murchison has been reported to be isotopically very heterogeneous24 and this might explain the much larger variations for δ13C values found for the methoxyl groups of Murchison. Similarly, mean δ13C values of CH3Cl emissions from terrestrial soil (ranging from −74 to −54‰) and Murchison (ranging from −19.2 to +10‰) on pyrolysis between 200 and 350°C were distinct from one another, (Fig. 5, Supplementary Table 1). Figure 6 shows a two-dimensional plot of the δ13C and δ2H values of CH3Cl emissions from the terrestrial environment and Murchison. Also shown are the predicted values for CH3Cl emissions from a biological Martian origin (for details of assumptions made see discussion). From this figure it is clear that isotopic signatures would be a powerful tool in constraining the origin of the organic matter precursor of CH3Cl derived from Martian soil.

Bottom Line: Controversy continues as to whether chloromethane (CH3Cl) detected during pyrolysis of Martian soils by the Viking and Curiosity Mars landers is indicative of organic matter indigenous to Mars.Thus CH3Cl emissions recorded by Mars lander experiments may be attributed to methoxyl groups in undegraded organic matter in meteoritic debris reaching the Martian surface being converted to CH3Cl with perchlorate or chloride in Martian soil.However we cannot discount emissions arising additionally from organic matter of indigenous origin.

View Article: PubMed Central - PubMed

Affiliation: 1] Institute of Earth Sciences, University of Heidelberg, Im Neuenheimer Feld 234-236, 69120 Heidelberg, Germany [2] Max-Planck-Institute for Chemistry, Hahn-Meitner-Weg 1, 55128 Mainz, Germany.

ABSTRACT
Controversy continues as to whether chloromethane (CH3Cl) detected during pyrolysis of Martian soils by the Viking and Curiosity Mars landers is indicative of organic matter indigenous to Mars. Here we demonstrate CH3Cl release (up to 8 μg/g) during low temperature (150-400°C) pyrolysis of the carbonaceous chondrite Murchison with chloride or perchlorate as chlorine source and confirm unequivocally by stable isotope analysis the extraterrestrial origin of the methyl group (δ(2)H +800 to +1100‰, δ(13)C -19.2 to +10‰,). In the terrestrial environment CH3Cl released during pyrolysis of organic matter derives from the methoxyl pool. The methoxyl pool in Murchison is consistent both in magnitude (0.044%) and isotope signature (δ(2)H +1054 ± 626‰, δ(13)C +43.2 ± 38.8‰,) with that of the CH3Cl released on pyrolysis. Thus CH3Cl emissions recorded by Mars lander experiments may be attributed to methoxyl groups in undegraded organic matter in meteoritic debris reaching the Martian surface being converted to CH3Cl with perchlorate or chloride in Martian soil. However we cannot discount emissions arising additionally from organic matter of indigenous origin. The stable isotope signatures of CH3Cl detected on Mars could potentially be utilized to determine its origin by distinguishing between terrestrial contamination, meteoritic infall and indigenous Martian sources.

No MeSH data available.


Related in: MedlinePlus