NASA ASTEP - Shallow-Borehole Array for Measuring Greenland Emission of Trace Gases as an Analogue for Methane on Mars (Project GETGAMM)
Planetary exploration of Mars has advanced rapidly in the past decade with high-resolution data from orbiting and landed instruments upending the image of a monotonously arid red planet and raising interest in a search for evidence of past or present Martian life. Cratered landscapes dissected by abandoned channels and active gullies, sedimentary sequences containing phyllosilicate and evaporate minerals, and plumes of atmospheric methane are tantalizing clues about the habitability potential for dynamic Mars. Plausible pathways and relative importance of biotic and abiotic processes during origination and destruction of CH4 on Mars remain highly contentious issues in the scientific community. Nevertheless, treating volatile emissionsas potential atmospheric biomarkers is prudent for planetary protection and is critical for exploration strategies aimed at life detection. The combined objectives of planetary protection and life detection require development, testing and refinement of new instrumental methods for directly determining the concentration and isotopic composition of methane, and other reduced trace gases, in Martian samples collected from the lower atmosphere and in shallow boreholes. During our 3-year field campaign in southwest Greenland (Figure 1) we will analyze seasonal and diurnal variations in concentrations and isotopic compositions of CH4, C2H6, and H2S in bedrock boreholes (0.5 to 2 m depth) and soil pipe wells (1 to 1.5 m depth) intersecting permafrost environments across a study site of about 1 km2. Results of this study in Greenland are fundamental to engineering and scientific preparation for shallow drilling on Mars currently under consideration for future mid-range rover missions.
During the 2011 site-selection campaign in Greenland, laser spectroscopy was used to map CH4 emissions, and the orientation of fracture zones and mafic units at the study site were mapped in detail. During the 2012 campaign this spring pipe wells will be hand inserted, instrumented and sealed at 2 wet- and 2 dry-soils locations for testing of gas transfer to instruments via capillary tubes. During the 2012 drilling campaign, data from Open Path Laser (OPL) mapping will be used to target soil and bedrock sites for measurement of reduced gases, temperature, and pressure. Bedrock boreholes at 3 sites will be drilled percussively with instrumentation and sealing done by hand. Each borehole or well will have one fiber optic line and two capillary lines installed by hand through an inert screw-compression seal. The capillary lines will be used to transfer gas into detection instruments at the surface and the fiber optic line will allow transfer of data from temperature and pressure sensors to data loggers. During the 2013 campaign, bedrock boreholes will be drilled percussively with an integrated drill-packer-optic-capillary (DPOC) system as a technology demonstration of semi-autonomous drilling for planetary exploration. Carbon and hydrogen isotopic compositions for methane (CH 4 ) and ethane (C 2 H 6 ) will be determined in the field using commercial instruments for Integrated Cavity Output Spectroscopy (ICOS) (Los Gatos Inc.), and research instruments for Cavity Ring Down Spectroscopy (CRDS) from Goddard Space Flight Center and Princeton University and multi-path tunable laser called the Methane Carbon Isotope Laser Spectrometer (CH 4 CILS) from JPL.