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Project Progress

8:00-14:30 PDT NASA Ames Research Center, California, USA
11:00-17:30 EDT NASA Goddard Space Flight Center, Maryland, USA
16:00-23:30 CEST Centro de Astrobiologia del CSIC-INTA, Madrid Spain

Introductory remarks (10 mins; 8:00 PDT/11:00 EDT/17:00 CEST)

Bruce Runnegar, NASA Astrobiology Institute, Ames Research Center, Moffett Field, CA 94035, USA; Bruce.Runnegar@nasa.gov

Spectral observations of methane on Mars (45 + 15 mins; 8:10/11:10/17:10)

Michael J. Mumma, Solar System Exploration Division and Goddard Center for Astrobiology, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
Michael.J.Mumma@nasa.gov

Abstract: Three groups have reported independent detections of methane on Mars. I will review the current status of these searches. On Mars, the photochemical lifetime of methane is very short (~300 years), and any methane now in its atmosphere must have been released within that time. However, the lifetime could be very much shorter if heterogeneous processes destroy methane efficiently, and this would require that estimated production rates be revised upwards. I will present evidence supporting the presence of strong latitudinal (meridional) gradients, obtained by our team. These gradients require: 1. significant local sources of methane, and 2. a removal mechanism that is much more rapid than photochemistry. The destruction lifetime might be shorter than the meridional circulation time (of order weeks), i.e., several thousand times faster than photochemistry and this provides an important quantitative constraint for assessing the release rate. The combination provides an important constraint for assessing biogenic vs. primordial or geothermal origins.

Discussion (30 mins; 9:10/12:10/18:10)

Break (30 mins; 9:40/12:40/18:40)

Terrestrial analogs 1 — water-rock reactions (20 + 5 mins; 10:10/13:10/19:10)

Craig E. Manning, Department of Earth and Space Sciences, University of California, Los Angeles, CA 90095-1567, USA; manning@ess.ucla.edu

Terrestrial analogs 2 — deep crustal methane (20 + 5 mins; 10:35/13:35/19:35)

Barbara Sherwood-Lollar, Department of Geology, University of Toronto, Ontario, Canada M5S 3B1; bslollar@chem.utoronto, ca

Resolving abiogenic versus biogenic sources of methane and implications for Mars exploration.

Sherwood Lollar, B.¹, Telling, J.¹, Lacrampe-Couloume, G.¹, Slater, G.F.², Onstott, T.C.³ and Pratt, L.M.⁴. (¹Department of Geology, 22 Russell St., University of Toronto, Toronto, Ontario Canada M5S 3B1 bslollar@chem.utoronto.ca. ²School of Geography and Geology, McMaster University, Hamilton, Ontario L8S 4K1. ³Dept. of Geosciences, Guyot Hall, Princeton University, Princeton NJ 08544. ⁴Dept. of Geological Sciences, Indiana University, Bloomington IN 47405). Bslollar@chem.utoronto.ca

Abstract: To date the characteristics of abiogenic hydrocarbons have not been well defined. Studies of terrestrial abiogenic gases have shown that measuring the delta ¹³C value of methane alone is not always diagnostic. If the source of carbon is mantle-derived, as at the mid-ocean spreading centers, the delta ¹³C value of the methane would be expected to be relatively enriched in ¹³C. Away from mantle carbon input however, in crustal-dominated systems such as deep Precambrian Shield rocks, processes of water-rock interaction (including serpentinization) produce abiogenic hydrocarbons that may have much more isotopically light (¹²C-rich) signatures, reflecting local crustal carbon sources. Drawing on field data from terrestrial abiogenic gases and recent laboratory experiments, this paper will address key parameters that may be used as diagnostic tools for identifying biogenic hydrocarbons versus abiogenic geological sources of methane and other hydrocarbons, in particular the pattern of ¹³C and ²H variation between methane and higher hydrocarbon gases such as ethane.

Terrestrial analogs 3 – biogenic methane (20 + 5 mins: 11:00/14:00/20:00)

Christopher H. House, Department of Geosciences, Pennsylvania State University, University Park, PA 16802, USA; chouse@geosc.psu.edu

Abstract: Methanogens, members of the Euryarchaeota, inhabit diverse of anaerobic habitats on Earth ranging from polar sediments to hydrothermal vents. The phylogenetic, environmental, and metabolic diversity of methanogens and methanotrophs will be discussed. Also, an overview of carbon isotopic fractionation during methanogenesis will be presented.

Fate of Disequilibrium Trace Gases in the Martian Atmosphere (20 + 5 mins; 11:25/14:25/20:25)

Michael E. Summers, School of Computational Sciences, Department of Physics and Astronomy, George Mason University, Fairfax, Va 22030

Abstract: The recent discovery of methane in the atmosphere of Mars has provided a new approach for indirectly probing possible disequilibrium chemistry beneath the Martian surface. Methane in the Martian atmosphere has a chemical lifetime of less than about 300 Earth years, thus its existence in the atmosphere may suggest a continuous replenishment. Its chemical lifetime is several orders of magnitude longer than typical atmospheric transport timescales, and thus its mixing ratio is to first order expected be fairly uniform throughout the Martian lower atmosphere, except possibly near localized source regions. A measurement of its average value would thus provide an estimate of the total magnitude of its source. In order to use measurements of methane as a probe of its source strength, it is important to understand its fate in the atmosphere. The chemical destruction of methane in the terrestrial atmosphere has been extensively studied. Analogous processes are likely to dominate the destruction of gaseous methane on Mars. Specifically, ultra-violet photolysis and chemical reactions between methane and both OH (hydroxyl) and O(¹D) are probable loss processes on Mars. The oxidation of Martian methane will have an inconsequential impact on the overall chemical structure of the atmosphere, but understanding the details of the oxidation process may provide a means to use measurements of small variations of atmospheric methane to locate source regions. Also, understanding the kinetics of methane chemical destruction on Mars also provides a theoretical framework for understand the chemical loss of other possible disequilibrium gases such as H₂S, NH₃, HCN, and CH₂O, that might exist in the Martian atmosphere. These latter species probably have chemical lifetimes substantially shorter than that of methane, and their distributions in the Martian atmosphere will probably show strong correlations with their respective source regions. And finally, understanding the isotopic fractionation of methane in the Martian atmosphere may provide a means to use isotopic measurements as constraints on the nature of the methane source.

Break (30 Mins; 11:50/14:50/20:50)

Working session/brief contributions (120 Mins; 12:20/15:20/21:20)

Summary and closing remarks (10 mins; 14:20/17:20/23:20)