NASA Astrobiology Institute (NAI)

1. Isotopic Signatures of Methane and Higher Hydrocarbon Gases from Precambrian Shield Sites: A Model for Abiogenic Polymerization of Hydrocarbons

   Project Investigators: Barbara Sherwood Lollar, Ken Voglesonger

   Other Project Members

   G Lacrampe-Couloume (Research Staff)

   Tullis Onstott (Collaborator)

   Lisa Pratt (Collaborator)

   Stefanie Tille (Doctoral Student)

   Summary

   Methane and higher hydrocarbon gases in ancient rocks on Earth originate from both biogenic and abiogenic processes. The measured carbon isotopic compositions of these natural gases are consistent with formation of polymerization of increasing long hydrocarbon chains starting with methane. Integration of carbon isotopic compositions with concentration data is needed to delineate the origin of hydrocarbon gases.

   Astrobiology Roadmap Objectives:

   • Objective 1.1: Models of formation and evolution of habitable planets
   • Objective 2.1: Mars exploration
   • Objective 3.1: Sources of prebiotic materials and catalysts
   • Objective 4.1: Earth's early biosphere
   • Objective 4.2: Foundations of complex life
   • Objective 6.1: Environmental changes and the cycling of elements by the biota, communities, and ecosystems
   • Objective 7.1: Biosignatures to be sought in Solar System materials
   • Objective 7.2: Biosignatures to be sought in nearby planetary systems

   Project Progress

   Isotopic Signatures of Methane and Higher Hydrocarbon Gases from Precambrian Shield Sites: A Model for Abiogenic Polymerization of Hydrocarbons

   Previous studies of methane (CH₄) and higher hydrocarbon gases in Precambrian Shield rocks in Canada and the Witwatersrand Basin of South Africa identified both microbial and abiogenic origins for gas types. Relatively fresh paleometeoric waters were dominated by hydrocarbon gases with compositional and isotopic characteristics consistent with production by methanogenic microbes utilizing a CO₂ reduction pathway. In contrast, the deepest and most saline fracture waters contained gases that did not resemble the products of microbial methanogenesis and were characterizedg by high concentrations of both H₂ and CH₄ gas and by isotopic compositions of CH₄ and higher hydrocarbon gases aligned with abiogenic processes in water-rock reactions at high rock/water ratios.. Based on new data obtained for the higher hydrocarbon gases in particular, a model is proposed to account for carbon isotope variation between CH₄ and the higher hydrocarbon gases (specifically ethane, propane, butane, and pentane) consistent with abiogenic polymerization. Values of δ¹³C for CH₄ and the higher hydrocarbon gases predicted by the model are shown to match proposed abiogenic hydrocarbon gas end-members identified at 5 field sites (2 in Canada and 3 in South Africa) suggesting that the carbon isotope patterns between the hydrocarbon homologues reflect the reaction mechanism. Recent experimental and field studies of proposed abiogenic hydrocarbons such as those found at mid-ocean spreading centers and off-axis hydrothermal fields such as Lost City have begun to focus not only on the origin of CH₄ but on the compositional and isotopic information contained in the higher hydrocarbon gases. Although the extent of fractionation in the first step in the hydrocarbon synthesis reaction chain may vary as a function of different reaction parameters, δ¹³C values for the higher hydrocarbon gases may be predicted by a simple mass balance model from the δ¹³C values of the lower molecular weight precursors, consistent with abiogenic polymerization. Integration of isotopic data for the higher hydrocarbon gases in addition to CH₄ may be critical for delineation of the origin of the hydrocarbons and investigation of formation mechanisms.

   
   

   Measured carbon isotope values (black squares and dotted lines) plotted versus carbon number for the straight chain alkanes— methane (C1), ethane (C2), propane (C3), n-butane (n-C4) and n-pentane (n-C5) for Kidd Creek gases. Errors are ±0.5& for d13C values. Carbon isotope values calculated based on the polymerization model equations in Table 2 are shown as open circles and solid lines. The model reproduces the C1–C2 depletion trend and C2–C5 enrichment trend in 13C for straight chain alkanes, although the calculated d13C values for n-C5 are more depleted in 13C than measured values.

   Mission Involvement

   AFL

   Sherwood Lollar is collaborating closely with Onstott on testing a Cavity Ring Down Spectrometer in both laboratory and field settings as an instrument that could be landed on the surface of Mars and used for determining the isotopic composition of methane.

   Field Expeditions

   Name

   Geochemical and microbiological investigation of high salinity endmember groundwaters in the Precambrian Canadian Shield

   Dates

   8/26/07 - 8/29/07

   Location

   48o28’N 81o20’W

   Description

   Integrated geochemical and microbiological sampling of boreholes of with the highest salinities at the 7900 ft level of Kidd Creek Mine.

   Name

   Sampling deep groundwaters in the Birchtree mine for gases, fluids, and biomass – geochemical and microbiological characterization of the deep biosphere

   Dates

   11/5/07 - 11/11/07

   Location

   50o45’N 97o52’W

   Description

   Integrated geochemical and microbiological sampling of boreholes discharging gas and water at the 3900 ft.level of the Birchtree Mine. Large-scale filtration of fluids for the collection of biomass to for DNA and PFLA collection. Deployment of in situ biofilm units for increased collection of biomass. Collecting of drill core samples for isotopic analyses. Collecting the noble gas samples.

   Name

   Microbiological sampling of the deep biosphere in an ultramafic setting

   Dates

   1/9/08 - 1/11/08

   Location

   50o45’N 97o52’W

   Description

   Recovery and deployment of biofilm units for DNA and PLFA analyses at the 3900 ft level of the Birchtree Mine.

   Name

   Geochemical and microbiological investigation of deep fracture waters in the Precambrian Canadian Shield

   Dates

   2/9/08 - 2/14/08

   Location

   48o28’N 81o20’W

   Description

   Integrated geochemical and microbiological sampling of boreholes with the highest salinities at the 7900 ft level of Kidd Creek Mine. Deployment of biofilm units for increased collection of biomass. Collecting the noble gas samples.

   Name

   Sampling deep groundwaters in the Birchtree mine for gases, fluids, and biomass – geochemical and microbiological characterization of the deep biosphere

   Dates

   3/24/08 - 3/28/08

   Location

   50o45’N 97o52’W

   Description

   Geochemical and microbiological sampling of boreholes discharging gas and water at the 3900 ft.level of the Birchtree Mine. Large-scale filtration of fluids for the collection of biomass to for DNA and PFLA collection. Deployment of in situ biofilm units for increased collection of biomass. Collecting of drill core samples for isotopic analyses.

   Name

   Microbial and geochemical sampling in the Canadian High Arctic: Analogues for Mars simulator testing

   Dates

   4/23/08 - 5/2/08

   Location

   79º26'N 90º46'W

   Description

   Geochemical and microbiological sampling in methane seeps and springs in the Canadian High Arctic

   Name

   Geochemical and microbiological investigation of deep fracture waters in the Precambrian Canadian Shield

   Dates

   6/18/08 - 6/21/08

   Location

   48o28’N 81o20’W

   Description

   Integrated geochemical and microbiological sampling of boreholes of with the highest salinities at the 7900 ft level of Kidd Creek Mine. Deployment of biofilm units for increased collection of biomass. Collecting the noble gas samples.

   Cross-Team Collaborations

   1) Collaboration with Dr. T. McCollom of the University of Colorado, Boulder team to measure the isotopic signatures of abiotic organic synthesis under geologic conditions. (Discussed in Sherwood Lollar,B. & McCollom, T.M. Biosignatures and abiotic constraints on early life.(2006) Nature 444:E18. Dec 14, 2006). Experimental results in prep for submission to EPSL.

   2) Collaboration with Dr. P. Morrill, Dr. O. Johnson, Dr. J. Eigenbrode and Dr. M. Fogel from the Carnegie Institute of Washington team to research biogeochemical carbon cycling in ultrabasic reducing springs in Sonoma County CA. (Presented at the meeting of the American Geophysical Union. San Francisco CA, Dec. 2006.) Morrill, P.L., Johnson, O.J., Cotton, J., Eigenbrode, J.L., Nealson, K.H., Sherwood Lollar, B. and Fogel, M.L. Microbial hydrocarbons in ultra-basic reducing water at a continental site of active serpentinization in N. California. (in review GCA).

   3) Collaboration with Dr. P. Morrill, Dr. D. Weinberger, Dr. M. Fogel and Dr. G. Cody from the Carnegie Institute of Washington team to investigate experimental abiogenic synthesis and stable carbon and hydrogen isotope values of gaseous hydrocarbons and the implications for identifying biosignatures. (Presented at the meeting of the American Geophysical Union. San Francisco CA, Dec. 2006.) Experimental results in prep for submission to GCA.

   4) Collaborations with the Pennsylvania State and University of Minneesota team include collaborative experiments with Dr. William Seyfried on synthesis of abiogenic hydrocarbons (Results presented in: Abiotic formation of hydrocarbons under hydrothermal conditions: Constraints from chemical and isotope data (2007). Geochimica Cosmochimica acta Vol.71:1982-1998.)

   5) Collaboration with the Pennsylvania State team include collaborative analysis via FISH-SIMS (C.House) and position specific δ13C analysis of acetate (K. Freeman, B. Thomas) on samples from Birchtree and Kidd Creek.

Publications

Unknown type: Film or Broadcast (21)

Fu, Q.  (2007).  Abiotic formation of hydrocarbons under hydrothermal conditions: Constraints from chemical and isotope data.  Geochimica Cosmochimica Acta, 71:1982-1998.

Lacrampe-Couloume, G.  (2008).  Microbial methanogenesis in ancient groundwaters in Witwatersrand Basin.  AbSciCon.  San Jose CA.

Lippmann-Pipke, J.  (in prep).  Neon isotopes identify deep Archean crustal fluids and date abiogenic hydrocarbons.  Nature.

Moran, J.  (2008).  Ancient analogs for ultramafic-hosted vents: Water-rock-derived energy for deep subsurface chemosynthesis..  18th Annual V. M. Goldschmidt Conference,.  Vancouver BC.

Morrill, P.  (2008).  Carbon isotope fractionation associated with abiogenic production of CH4: when abiogenic reduced carbon can be a biological look-alike..  AbSciCon.  San Jose CA.

Morrill, P.L.  (2008).  Isotopic evidence of microbial methane in ultra-basic reducing waters at a continental site of active serpentinization in N. California.  18th Annual V. M. Goldschmidt Conference.  Vancouver BC.

Perreault, N.N.  (submitted).  Heterotrophic and autotrophic microbial populations in cold perennial springs of the High Arctic.  AEM.

Pfiffner, S.  (in press).  Permafrost drilling at High lake mine, Nunavut.  Astrobiology.

Sherwood Lollar, B.  (2007).  Hydrogeologic controls on episodic H2 release from Precambrian fractured rocks - Energy for deep subsurface life on Earth and Mars.  Astrobiology, 7:971-986.

Sherwood Lollar, B.  (2008).  Isotopic signatures of CH4 and higher hydrocarbon gases from Precambrian Shield sites: A model for abiogenic polymerization of hydrocarbons.  Geochimica Cosmochimica Acta:doi:10.1016/j.gca.2008.07.004.

Sherwood Lollar, B.  (2008).  Deep abiotic synthesis of organic molecules, and the abiotic-biotic controversy.  Keynote. Deep Carbon Cycle Sloan Foundation Workshop. Carnegie Institute of Washington.  Washington DC.

Sherwood Lollar, B.  (2008).  Methane and Life?: Constraints from higher hydrocarbon gases and associated trace gases.  AbSciCon.  San Jose CA.

Voglesonger, K.M.  (2008).  Geochemistry of the deep "cool" biosphere of Precambrian Shield fracture waters: Terrestrial analogues for subsurface environments on Mars.  AbSciCon.  San Jose CA.