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Project Progress

Challenges for Coring Deep Permafrost on Earth and Mars: Drilling Project at High Lake, Nunavut, Canada

A scientific drilling expedition to the High Lake region of Nunavut, Canada, was completed in August of 2006 with the goal of collecting samples and delineating gradients in salinity, gas composition, pH, pe and microbial abundance in a 400 m thick permafrost zone, and to access the underlying pristine sub-permafrost brine. With a triple-barrel wire line tool and the use of stringent QA/QC protocols, 200 m of frozen, Archean, mafic volcanic rock was collected from the lower boundary that separates the permafrost layer and sub-permafrost saline water. Hot water was used to remove cuttings and prevent the drill rods from freezing in place. No cryopegs were detected during penetration through the permafrost. Coring stopped at the 535 m depth, and the drill water was bailed from the hole while saline water replaced it. Within 24 hours, the borehole iced closed at 125 m depth due to vapor condensation from atmospheric moisture and, initially, warm water leaking through the casing, which blocked further access. Preliminary data suggest that the recovered cores contain viable anaerobic microorganisms that are not contaminants even though isotopic analyses of the saline borehole water suggests that it is a residue of the drilling brine used to remove the ice from the upper, older portion of the borehole. Any proposed coring mission to Mars that seeks to access subpermafrost brine will not only require borehole stability, but also a means by which to generate substantial heating along the borehole string to prevent closure of the borehole from condensation of water vapor generated by drilling. A paper describing these results has just been published in Astrobiology.
Complete pore water analyses of the permafrost rock has been combined with ³⁵S microautoradiography to obtain a vertical profile of microbial sulfate reduction rates which reveals increasing rates with depth. These results were presented at the 2007 ASM in Toronto and at AbSciCon 2008.

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