use of sterile liners and other sterile devices for obtaining sample cores (for solids) or liquids. Most protocols for sample cores recommend further processing of the core under sterile conditions and removing interior portions for actual microbiological analysis. The inclusion of tracer studies to complement and track possible contamination during any deep-biosphere sampling is also an extremely important step in most protocols examined.

Current levels of cleanliness associated with planetary protection standards are not feasible for the exploration of subglacial aquatic environments. Although it may be possible to control the initial number of cells associated with drilling and sampling equipment using current technologies, it is not possible to prevent the transfer and distribution of cells between different strata in the borehole during the drilling and sampling processes. Drilling and sampling equipment can be cleaned prior to entering the ice, but the extreme depths achieved during drilling and the fact that the drilling hardware is inaccessible for subsequent cleaning make stringent bacterial cleanliness requirements such as those implemented in space research unrealistic.

The hydrodynamic nature of subglacial aquatic environments facilitates cell transfer from any object that may find its way into liquid water. If the lake has unique biological ecosystems, transfer may also occur as a robotic sampling device moves from ecosystem to ecosystem. In general, requirements for cleanliness will have to be addressed in terms of (1) cleaning hardware (quantification of bacterial levels and bacterial diversity present) prior to penetration, (2) maintaining hardware cleanliness as much as possible during penetration, and (3) designing research techniques that minimize the possibility of cell transfer between different levels in the ice and the lake bed itself. Specific decontamination techniques need to be developed for any instruments deployed in a subglacial aquatic environment. The current decontamination approaches include sterilization by heat (autoclave) and/or chemical treatment (peroxide). The instrument packages must be robust to maintain their operational specifications following these decontamination protocols.

A critical aspect of subglacial lake exploration and technology development is testing, verification, and monitoring of potential contamination during all phases of the scientific program. There must be deliberate and careful scrutiny of the methodologies employed, from ice drilling to sample recovery, from both an environmental stewardship and a scientific standpoint. Stewardship issues include providing the maximum possible protection of subglacial lake environments by ensuring minimal alteration or change due to the planned scientific studies. From a scientific standpoint, it is essential that uncompromised samples be provided for study and that the presence of human-made devices does not bias the data collected. There is also concern that unusual or previously unknown biological agents be properly handled upon retrieval to avoid an unwanted release to the environment.

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