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Perchlorate and volatiles of the brine of Lake Vida (Antarctica): Implication for the in situ analysis of Mars sediments
Author(s) -
Kenig Fabien,
Chou Luoth,
McKay Christopher P.,
Jackson W. Andrew,
Doran Peter T.,
Murray Alison E.,
Fritsen Christian H.
Publication year - 2016
Publication title -
journal of geophysical research: planets
Language(s) - English
Resource type - Journals
eISSN - 2169-9100
pISSN - 2169-9097
DOI - 10.1002/2015je004964
Subject(s) - perchlorate , solid phase microextraction , mars exploration program , chemistry , brine , environmental chemistry , gas chromatography , mass spectrometry , gas chromatography–mass spectrometry , geology , chromatography , astrobiology , organic chemistry , ion , physics
The cold (−13.4°C), cryoencapsulated, anoxic, interstitial brine of the >27 m thick ice of Lake Vida (Victoria Valley, Antarctica) contains 49 µg · L −1 of perchlorate and 11 µg · L −1 of chlorate. Lake Vida brine (LVBr) may provide an analog for potential oxychlorine‐rich subsurface brine on Mars. LVBr volatiles were analyzed by solid‐phase microextraction (SPME) gas chromatography–mass spectrometry (GC‐MS) with two different SPME fibers. With the exception of volatile organic sulfur compounds, most other volatiles observed were artifacts produced in the GC injector when the thermal decomposition products of oxychlorines reacted with reduced carbon derived from LVBr and the SPME fiber phases. Analysis of MilliQ water with perchlorate (40 µg · L −1 ) showed low level of organic artifacts, reflecting carbon limitation. In order to observe sample‐derived organic compounds, both in analog samples and on Mars, the molar abundance of reduced carbon in a sample must exceed those of O 2 and Cl 2 produced during decomposition of oxychlorines. This suggests that the abundance of compounds observed by the Sample Analysis at Mars (SAM) instruments in Sheepbed samples (CB‐3, CB5, and CB6) may be controlled by an increase in the reduced‐carbon/oxychlorine ratio of these samples. To increase chances of in situ detection of Martian organics during pyrolysis‐GC‐MS, we propose that the derivatization agents stored on SAM may be used as an external source of reduced carbon, increasing artificially the reduced‐carbon to perchlorate ratio during pyrolysis, allowing the expression of more abundant and perhaps more diverse Martian organic matter.