VALKYRIE (Very-deep Autonomous Laser-powered Kilowatt-class Yo-yoing Robotic Ice Explorer) is a NASA-funded project to develop key technologies for an autonomous ice penetrator, or cryobot, capable of delivering science payloads through outer planet ice caps and terrestrial glaciers. This 4 year effort will produce a cylindrical cryobot prototype 280 cm in length and 25 cm in diameter. One novel element of VALKYRIE’s design is the use of a high-energy laser as the primary power source. 1070 nm laser light is transmitted at 5 kW from a surface-based laser and injected into a custom-designed optical waveguide that is spooled out from the descending cryobot. Light exits the downstream end of the fiber, travels through diverging optics, and strikes an anodized aluminum beam dump, which channels thermal power to hot-water jets that melt the descent hole. Some beam energy is converted to electricity via photovoltaic cells, for running on-board electronics and jet pumps. Since the vehicle can be sterilized prior to deployment, and forward contamination is minimized as the melt path refreezes behind the cryobot, expansions on VALKYRIE concepts may enable cleaner access to deep subglacial lakes. This paper focuses on laser delivery and beam dump thermal design.

There is significant interest in sampling subglacial environments for geobiological studies, but they are difficult to access. Existing ice-drilling technologies make it cumbersome to maintain microbiologically clean access for sample acquisition and environmental stewardship of potentially fragile subglacial aquatic ecosystems. The IceMole is a maneuverable subsurface ice probe for clean in situ analysis and sampling of glacial ice and subglacial materials. The design is based on the novel concept of combining melting and mechanical propulsion. It can change melting direction by differential heating of the melting head and optional side-wall heaters. The first two prototypes were successfully tested between 2010 and 2012 on glaciers in Switzerland and Iceland. They demonstrated downward, horizontal and upward melting, as well as curve driving and dirt layer penetration. A more advanced probe is currently under development as part of the Enceladus Explorer (EnEx) project. It offers systems for obstacle avoidance, target detection, and navigation in ice. For the EnEx-IceMole, we will pay particular attention to clean protocols for the sampling of subglacial materials for biogeochemical analysis. We plan to use this probe for clean access into a unique subglacial aquatic environment at Blood Falls, Antarctica, with return of a subglacial brine sample.

The proposed RECoverable Autonomous Sonde (RECAS) will allow analysis and sampling of subglacial water while the subglacial lake remains isolated from the surface. The probe is equipped with two electrically heated melting tips, one on the bottom and one on the top of a cylindrical probe. When one of the tips is powered, the RECAS moves up or down similarly to a hot-point thermal electric drill. The electric power and signal cable is coiled inside the probe on an electric-motor-powered coil. When the lower tip is powered, the probe advances downwards by gravity. In order to move the probe up, power is applied to the upper heated tip and the coil motor pulls the cable, moving the probe upwards and melting the borehole above the probe. A conventional internal combustion engine electric generator on the glacier surface provides 9–10 kW of power to the RECAS via an umbilical cable stored in the probe. Electric power enables a penetration rate of 2.4–2.9m h–1, and thus 4–5 months will be required to reach a depth of 3500 m and return to the surface.

The introduction of low-temperature fluid into boreholes drilled in ice sheets helps to remove drilling cuttings and to prevent borehole closure through visco-plastic deformation. Only special fluids, or mixtures of fluids, can satisfy the very strict criteria for deep drilling in cold ice. The effects of drilling fluid on the natural environment are analyzed from the following points of view: (1) occupational safety and health; (2) ozone depletion and global warming; (3) chemical pollution; and (4) biological pollution. Traditional low-temperature drilling fluids (kerosene-based fluids with density additives, ethanol and n-butyl acetate) cannot be qualified as intelligent choices from the safety, environmental and technological standpoints. This paper introduces a new type of low-temperature drilling fluid composed of synthetic ESTISOLTM esters, which are non-hazardous substances. ESTISOLTM 140 mixtures with ESTISOLTM 165 or ESTISOLTM F2887 have an acceptable density and viscosity at low temperature. To avoid the potential for biological contamination of the subglacial environment, the borehole drilling fluid should be treated carefully on the surface.

Wireless sensors have the potential to provide significant insight into in situ physical and biogeochemical processes in sub-ice hydrologic systems. However, the nature of the glacial environment means that sensor deployment and data return is challenging. We describe two bespoke sensor platforms, electronic tracers or ‘ETracers’, and ‘cryoegg’, for untethered, wireless data collection from glacial hydrologic systems, including subglacial channels. Both employ radio frequencies for data transmission, are designed to endure harsh environmental conditions and can withstand low temperatures, high pressure, turbulence and abrasion. We discuss the design, optimization and field testing of the ETracers and cryoegg, culminating in test deployments beneath the Greenland ice sheet. The small, low-cost ETracers were able to travel through subglacial drainage channels, from where they returned water pressure measurements through 100 m of ice, and could measure water depth in crevasses. The larger cryoegg was able to return multi-parameter data from moulins through 500 m of wet ice to receivers up to 2 km away, and from 12 m depth in a proglacial lake to a receiver on the shore. The tests demonstrate that the cryoegg and ETracers are low-power, versatile, robust wireless sensor platforms suitable for glacial environments, which may be used with portable, low-cost receiving equipment.

A clean hot-water drill was used to gain access to Subglacial Lake Whillans (SLW) in late January 2013 as part of the Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) project. Over 3 days, we deployed an array of scientific tools through the SLW borehole: a downhole camera, a conductivity–temperature–depth (CTD) probe, a Niskin water sampler, an in situ filtration unit, three different sediment corers, a geothermal probe and a geophysical sensor string. Our observations confirm the existence of a subglacial water reservoir whose presence was previously inferred from satellite altimetry and surface geophysics. Subglacial water is about two orders of magnitude less saline than sea water (0.37–0.41 psu vs 35 psu) and two orders of magnitude more saline than pure drill meltwater (<0.002 psu). It reaches a minimum temperature of –0.55~C, consistent with depression of the freezing point by 7.019 MPa of water pressure. Subglacial water was turbid and remained turbid following filtration through 0.45 µm filters. The recovered sediment cores, which sampled down to 0.8 m below the lake bottom, contained a macroscopically structureless diamicton with shear strength between 2 and 6 kPa. Our main operational recommendation for future subglacial access through water-filled boreholes is to supply enough heat to the top of the borehole to keep it from freezing.

In the early hours of 25 December 2012, an attempt to explore Subglacial Lake Ellsworth, West Antarctica, using a specially designed hot-water drill, was halted. This UK project, involving several universities, the British Antarctic Survey and the National Oceanography Centre, had been in planning for 10 years. The project developed a full blueprint for subglacial lakes research, involving access to the subglacial environment through deep drilling, direct measurement and sampling of water and sediment by the construction of a probe and sediment corer, and environmental protocols to ensure cleanliness in line with international agreements on stewardship and protection of subglacial systems. Drilling was ceased after the main borehole failed to link with a subsurface cavity of water, built up over ∽40 hours. Without this link, insufficient water was available to continue drilling downwards to the lake, ∽3000 m beneath the surface. On return to the UK, an external review of the programme was undertaken to formally assess the reasons for the fieldwork failure, and to make recommendations on the modifications necessary for success. From this review, the Lake Ellsworth programme formulated a pathway along which a second attempt to explore the lake can be developed. Here details of the Lake Ellsworth field experiment, the circumstances that led to its failure and the corrections required are presented. Hot-water drilling is still regarded as the only feasible scheme for assuring clean access to the subglacial environment. The lessons learned from the Lake Ellsworth experience are substantial, however, and demonstrate that considerable technological and methodological advances are necessary for successful future research on subglacial lakes beneath thick (>2 km) ice.

Antarctic subglacial lakes are of great interest to the science community. These systems are considered to be in pristine condition, potentially harbouring an environment containing undisturbed sedimentary sequences and ecosystems adapted to cold oligotrophic environments in the absence of sunlight. Gaining access to subglacial lakes presents major technological challenges. To comply with conventions covering the exploration of pristine Antarctic environments, access should be conducted so the lake is not contaminated in any way. Consequently, all equipment to enter the lake must be sterile and the entrance should isolate the lake from the external environment. Currently, clean access to these environments is achieved using a hot-water drilling system. Differences between the hydraulic pressure head of the lake and the glacial surface result in a section of the borehole being air-filled. It is imperative that this section is disinfected prior to introducing any sampling equipment. This paper describes the design process involved in rapid-prototyping an ultraviolet (UV) disinfection reactor for achieving this goal. Considerations such as UV output, physical constraints, temperature management, and deployment procedures are assessed. We present a design that addresses these considerations.

This paper considers the state of the deep ice borehole 5G at the Russian Antarctic Vostok station after penetration to the surface water of Vostok Subglacial Lake. It discusses the peculiar features of drilling the ‘fresh frozen’ lake water that has risen in the borehole and the technology for subsequent study of the lake water layer via borehole 5G filled with a kerosene–Freon® mixture. The extremely high rise of lake water via the borehole is attributed to a hydraulic fracture at the side of the borehole, which diverted a large amount of drilling fluid. The proposed technology for the study of the water layer envisages minimal environmental impact and excludes penetration of any of the kerosene–Freon® mixture to the water layer. This technology has been presented several times at different international forums. There was no critical comment on the Environmental Impact Assessment of the technology at the 37th Antarctic Treaty Consultative Meeting in 2014 and it was adopted for implementation.