6 research outputs found
Isotopic and Geochemical Investigation of Two Distinct Mars Analog Environments Using Evolved Gas Techniques in Svalbard, Norway
The 2010 Arctic Mars Analog Svalbard Expedition (AMASE) investigated two distinct geologic settings on Svalbard, using methodologies and techniques to be deployed on Mars Science Laboratory (MSL). AMASErelated research comprises both analyses conducted during the expedition and further analyses of collected samples using laboratory facilities at a variety of institutions. The Sample Analysis at Mars (SAM) instrument suite on MSL includes pyrolysis ovens, a gas-processing manifold, a quadrupole mass spectrometer (QMS), several gas chromatography columns, and a Tunable Laser Spectrometer (TLS). An integral part of SAM development is the deployment of SAM-like instrumentation in the field. During AMASE 2010, two parts of SAM participated as stand-alone instruments. A Hiden Evolved Gas Analysis- Mass Spectrometer (EGA-QMS) system represented the EGA-QMS component of SAM, and a Picarro Cavity Ring Down Spectrometer (EGA-CRDS), represented the EGA-TLS component of SAM. A field analog of CheMin, the XRD/XRF on MSL, was also deployed as part of this field campaign. Carbon isotopic measurements of CO2 evolved during thermal decomposition of carbonates were used together with EGA-QMS geochemical data, mineral composition information and contextual observations made during sample collection to distinguish carbonates formation associated with chemosynthetic activity at a fossil methane seep from abiotic processes forming carbonates associated with subglacial basaltic eruptions. Carbon and oxygen isotopes of the basalt-hosted carbonates suggest cryogenic carbonate formation, though more research is necessary to clarify the history of these rocks
An international intercomparison of stable carbon isotope composition measurements of dissolved inorganic carbon in seawater
We report results of an intercomparison of stable carbon isotope ratio measurements in seawater dissolved inorganic carbon (δ 13CâDIC) which involved 16 participating laboratories from various parts of the world. The intercomparison involved distribution of samples of a Certified Reference Material for seawater DIC concentration and alkalinity and a preserved sample of deep seawater collected at 4000âm in the northeastern Atlantic Ocean. The betweenâlab standard deviation of reported uncorrected values measured with diverse analytical, detection, and calibration methods was 0.11â° (1Ď ). The multiâlab average δ 13CâDIC value reported for the deep seawater sample was consistent within 0.1â° with historical measured values for the same water mass. Application of a correction procedure based on a consensus value for the distributed reference material, improved the betweenâlab standard deviation to 0.06â°. The magnitude of the corrections were similar to those used to correct independent data sets using crossover comparisons, where deep water analyses from different cruises are compared at nearby locations. Our results demonstrate that the accuracy/uncertainty target proposed by the Global Ocean Observing System (Âą0.05â°) is attainable, but only if an aqueous phase reference material for δ 13CâDIC is made available and used by the measurement community. Our results imply that existing Certified Reference Materials used for seawater DIC and alkalinity quality control are suitable for this purpose, if a âCertifiedâ or internally consistent âconsensusâ value for δ 13CâDIC can be assigned to various batches.publishedVersio
Biogeochemical probing of microbial communities in a basalt-hosted hot spring at KverkfjĂśll volcano, Iceland
We investigated bacterial and archaeal communities along an iceâfed surficial hot spring at KverkfjĂśll volcanoâa partially iceâcovered basaltic volcano at VatnajĂśkull glacier, Iceland, using biomolecular (16S rRNA, apsA, mcrA, amoA, nifH genes) and stable isotope techniques. The hot spring environment is characterized by high temperatures and low dissolved oxygen concentrations at the source (68°C and <1 mg/L (Âą0.1%)) changing to lower temperatures and higher dissolved oxygen downstream (34.7°C and 5.9 mg/L), with sulfate the dominant anion (225 mg/L at the source). Sediments are comprised of detrital basalt, lowâtemperature alteration phases and pyrite, with <0.4 wt. % total organic carbon (TOC). 16S rRNA gene profiles reveal that organisms affiliated with Hydrogenobaculum (54%â87% bacterial population) and Thermoproteales (35%â63% archaeal population) dominate the microâoxic hot spring source, while sulfurâoxidizing archaea (Sulfolobales, 57%â82%), and putative sulfurâoxidizing and heterotrophic bacterial groups dominate oxic downstream environments. The δ13Corg (â° VâPDB) values for sediment TOC and microbial biomass range from â9.4â° at the spring's source decreasing to â12.6â° downstream. A reverse effect isotope fractionation of ~3â° between sediment sulfide (δ34S ~0â°) and dissolved water sulfate (δ34S +3.2â°), and δ18O values of ~ â5.3â° suggest pyrite forms abiogenically from volcanic sulfide, followed by abiogenic and microbial oxidation. These environments represent an unexplored surficial geothermal environment analogous to transient volcanogenic habitats during putative âsnowball Earthâ scenarios and volcanoâice geothermal environments on Mars