Effects of oxygen-containing salts on the detection of organic biomarkers on Mars and in terrestrial analogue soils

Autor: Dirk Schulze-Makuch, Mark A. Sephton, Wren Montgomery, Elizabeth A. Jaramillo, Samuel P. Kounaves, Samuel H. Royle
Přispěvatelé: Science and Technology Facilities Council (STFC), UK Space Agency
Rok vydání: 2019
Předmět:
Life Sciences & Biomedicine - Other Topics
Extraterrestrial Environment
010504 meteorology & atmospheric sciences
Perchlorate
Atacama
Martian soil
01 natural sciences
Pyrolysis–gas chromatography–mass spectrometry
Soil
chemistry.chemical_compound
MOLECULES
Oxidizing agent
Organic Chemicals
Geosciences
Multidisciplinary
010303 astronomy & astrophysics
ATACAMA DESERT
chemistry.chemical_classification
Perchlorates
Environmental Biomarkers
Pyrolysis-gas chromatography-mass spectrometry
Geology
Agricultural and Biological Sciences (miscellaneous)
MUDSTONE
Detection
Environmental chemistry
Physical Sciences
Desert Climate
Oxidation-Reduction
Pyrolysis
Life Sciences & Biomedicine
NITRATE
ROCKNEST AEOLIAN DEPOSIT
Mars
Astronomy & Astrophysics
Gas Chromatography-Mass Spectrometry
COMBUSTION
Organics
Exobiology
0103 physical sciences
0201 Astronomical and Space Sciences
0402 Geochemistry
Organic matter
GALE CRATER
Biology
0105 earth and related environmental sciences
Science & Technology
chemistry
0403 Geology
Space and Planetary Science
MARTIAN SOIL
Soil water
Leaching (metallurgy)
MATTER
Popis: The detection of chlorinated hydrocarbons by Curiosity on Mars has been attributed to the presence of unidentified indigenous organic matter. Similarly, oxychlorines on Earth have been proposed to be responsible for the apparent lack of organics in the Atacama Desert. The presence of perchlorate (ClO4-) poses a unique challenge to the measurement of organic matter due to the oxidizing power of oxychlorines during commonly used pyrolysis-gas chromatography-mass spectrometry (py-GC-MS) methods. Here, we show that perchlorates and other oxyanion salts inhibit the detection of organic compounds but that removing these problematic species prior to pyrolysis by using an optimal sample extraction duration and suitable ratios of water to sample mass enables analysis. We have characterized leached and unleached samples containing perchlorates from the Atacama Desert and have found that after leaching, the py-GC-MS chromatograms of the dried mineral residues show identifiable biomarkers associated with indigenous cyanobacteria. Samples which were pyrolyzed without leaching showed no detectable organic matter other than background siloxane and very weak or no trace of detectable polychlorinated benzenes. Dried sample residues remaining after leaching, the mineral matrix and water-insoluble organic matter, showed a strong organic response in all cases when analyzed by py-GC-MS. These residues are most likely the product of the pyrolysis of water-insoluble organics originally present in the samples. In addition, our results imply that previous soil analyses which contained high levels of oxyanions and concluded that organics were either not present or were present at extremely low levels should be reexamined.
Databáze: OpenAIRE
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