Challenges for Coring Deep Permafrost on Earth and Mars

Abstract

A scientific drilling expedition to the High Lake region of Nunavut, Canada, was recently completed with the goals of collecting samples and delineating gradients in salinity, gas composition, pH, pe, and microbial abundance in a 400 m thick permafrost zone and accessing the underlying pristine subpermafrost brine. With a triple-barrel wireline tool and the use of stringent quality assurance and quality control (QA/QC) protocols, 200 m of frozen, Archean, mafic volcanic rock was collected from the lower boundary that separates the permafrost layer and subpermafrost 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.

What do membrane lipids tell us about the microorganisms living in extreme environments?

“…Biomass estimates on non-surface sterilized core ranged from below detection for five cores and from 0.6 to 32.1 pmol g -1 for the remaining cores, while the surface sterilized core ranged from below detection to 1.3 pmol g -1 24 . The High Lake core had biomass estimates that were lower than estimates for in deep subsurface cores from the sandstones and shales in Colorado and Virginia ( <17 pmol PLFA g -1 ), and quartzite and carbon leader rock cores in South Africa ((0.7 -81 pmol g -1 ) 2,3,30 .…”

“…The total volume of water filtered varied from 300 to 800 liters. During July and August 2006, drilling commenced at a previously established borehole HLW-03-28 and details of the drilling operation and sample collections were described in Pfiffner et al 24 . Samples of drilling water and rock cores were stored on blue ice in a cooler located at the drill site until they were received at the core processing shed where the lipid samples were frozen with dry ice.…”

High Lake gossan deposit: An Arctic analogue for ancient Martian surficial processes?

“…1A). Although the permafrost at High Lake is $440 m thick (Pfiffner et al, 2008), drilling indicates that the gossan under study only extends to a depth of $1 m, and is thus confined to the seasonally frozen, active layer. Additionally, glacial scouring implies that any previous fractured, surface gossan was likely removed during glaciation.…”

“…Circles identify location of gossan samples collected in July 2007 and sample numbers for each location are indicated. The High Lake borehole was described inPfiffner et al (2008). Ore zones A-E are located inPetch (2005).…”

Astrobiology Special Collection: Instruments for In Situ Exploration of Planets

“…Some of the instruments described in these papers do give insights into the subsurface, but for many approaches, physical subsurface access is necessary. Pfiffner et al (2008) show how experience of deep-drill coring on Earth may be applied to Mars. Instruments that operate both on the surface and beneath it are described in the contribution from Elphic et al (2008), who consider neutron detectors for hydrogen (that might be water) and a gamma ray spectrometer for broad geochemical analysis.…”