Preserving the pristine nature of Antarctic subglacial ecosystems necessitates environmental stewardship during their exploration. SALSA will drill into and access subglacial Lake Mercer in a way that minimizes microbial and chemical contamination to the environment and retrieved samples. Although concern over inadvertent contamination of the larger subglacial hydrological network is partially allayed by the fact that the system is near the end of an active hydrologic catchment, SALSA’s hot water drill and clean access protocols have been specifically designed with environmental stewardship in mind.
SALSA will use an established clean access strategy that adopts three complementary technologies widely used in the food, dairy, and pharmaceutical industries: (i) filtration, (ii) ultraviolet light, and (iii) pasteurization. The filtration component of the water treatment system consists of large capacity 2 µm and 0.2 µm filters that are plumbed in series. After filtration, the water is routed through UV irradiation modules that provide high intensity exposure at germicidal wavelengths (185 nm and 254 nm). To facilitate hot water drilling, the cleaned water is pumped to heaters that increase its temperature to ~90 o C, which has the additional advantage that 99% of microorganisms are typically killed by this treatment. Prior to deployment, all instruments and equipment entering the lake will be cleaned thoroughly with 3% hydrogen peroxide, which is an effective disinfectant that harmlessly decomposes to H2O and O2.
Based on laboratory and field testing of the equipment and approach, SALSA’s clean access strategy is capable of removing and killing 99.9999% of microorganisms in the source water (i.e., snow and ice melt). All of the proposed methods are proven and have been demonstrated to reduce microorganisms to levels that meet the National Research Council recommendations and Scientific Committee on Antarctic Research’s Code of Conduct for microbiological cleanliness during the exploration of Antarctic subglacial aquatic environments.