Dedicated to the memory of Nikolay Vasiliev, who for many years led the deep drilling project at Vostok Station

Since the early 1950s, when extensive exploration of Antarctica began, drilling has become an integral part of many large-scale scientific projects carried out on the sixth continent. Thanks to the rapid development of drilling equipment and technology, numerous scientific discoveries have been made in the fields of paleoclimatology, geology, glaciology, and other natural sciences. Since 1968, the St. Petersburg Mining University has played a leading role in this area’s development, and several generations of ice drilling specialists were trained within its walls. One of the most outstanding was Nikolay Vasiliev, who led Antarctic research at the university from 2002 to 2021. His contribution to the development of ice core drilling in Antarctica cannot be overestimated. Professor Vasiliev’s extensive and highly creative work laid the foundation for many achievements in this field over the past 30 years. His path is a brilliant example of hard work and dedication to one’s cause. This article is a tribute to Professor Vasiliev, who is cherished by his friends and colleagues who had the good fortune to work and study with this talented person and scientist.

The paper is based on additional studies of mineral inclusions in the accretion ice sampled by deep drilling at Vostok Station in central Antarctica. The studies include X-ray microtomography of two mineral inclusions with identification of their mineral composition; analysis of clay minerals in the soft aggregate of the largest inclusion; and geochronological study of zircon grains. X-ray microtomography shows intact morphology of the inclusions in the ice core and their internal texture. The soft aggregate of the largest inclusion is characterized by the dominance of illite, intermediate concentrations of chlorite and small amounts of kaolinite. A notable feature is the absence of mixed-layer minerals typical of Antarctic coastal areas. The most valuable information is derived from new geochronological data and their integration with previous dating data. The detrital zircon U-Pb ages show strong probability peaks between 900 and 1100 Ma, while the detrital monazite ages are clustered between 1250 and 1450 Ma. Both of these age intervals correspond to the Rayner Orogeny.

In this paper, we present a new dataset on the stable water isotopic composition (δD and δ18O) in a sequence of subglacial Lake Vostok’s accreted ice (3538–3769 m) measured along three parallel ice cores. The high precision of the new data has allowed us to characterize the formation conditions of different sections of the ice. The whole lake ice interval may be divided into 3 zones: 1) “zone 0”, 3538.8–3549.8 m, is under the strong influence of the local water formed from melted meteoric ice likely entering from under the glacier on the lake’s west coast; 2) “zone 1” (accreted ice 1), 3549.8–3607.4 m, is experiencing significant variability due to the slightly different effective fractionation coefficient in the course of “water inclusions” in the ice matrix during the freezing process; 3) “zone 2” (accreted ice 2), 3607.4–3768.8 m, is under the influence of glacial melt water from the northern part of the lake and the hydrothermal flux from the lake’s bottom. We defined the exact boundary between the accreted ice 1 and ice 2, which corresponds to a sharp isotopic excursion at a depth of 3607.4 m. In this work, we present for the first time data on the “17O-excess” parameter in the lake ice and water, which allowed us to make a direct calculation of the equilibrium fractionation coefficient for oxygen 17 during water freezing.

The paper presents a review of the studies carried out in the area of the subglacial Lake Vostok (East Antarctica) to date. They include geophysical, glaciological, geodesic, and geological investigations. The most important geophysical investigations were carried out by the Polar Marine Geosurvey Expedition. They included reflection and refraction seismic, and also radio-echo sounding. The major contribution to the study of this region was made by American researchers, who in the 2000/01 field season performed a complex airborne geophysical survey on a regular network. Their work included magnetometric, gravimetric, and radio-echo sounding measurements. All the research conducted found that the water surface area is 15 790 km², and its altitudinal height changes from –600 to –150 m. The average depth of Lake Vostok is 400 m, and the maximum marks reach 1 200 m. The water body volume is estimated at 6 100 km³. There are 11 islands in the lake, and their total area is 365 km². In addition, 56 isolated subglacial water bodies were found around the lake. A special section is devoted to a review of mathematical models of heat and mass transfer processes in the glacier and water movement in Lake Vostok.

The deep holes drilled at Vostok Station by the Russian Antarctic Expedition reached the surface of Subglacial Lake Vostok twice — on February 5, 2012 and January 25, 2015. Two unsealings of the largest subglacial water body on Earth, led by Nikolay Vasiliev, have become remarkable events in the history of Antarctic science. To preserve all the twists and turns of this pioneering work for the ice-drilling community, we have compiled and carefully analyzed all the available drilling, geophysical, and glaciological observations made prior to, during, and after the lake piercings. Based on that information, in this paper we have pieced together a detailed narrative of these two unprecedented drilling operations in the hope that the lessons learned may prove useful for future environmental stewardship, scientific investigations, and technological developments related to the exploration of Lake Vostok.

A study of the subglacial Lake Vostok requires clean accessing and sampling technologies. The paper presents four potential options — three types of hot-points and a hot-water drilling system — which can be considered as environmental-friendly technologies and could be used in the cold ice of East Antarctica. The description contains only general ideas and a brief estimation of the main parameters of the technologies suggested and does not include any detailed analysis. All the methods proposed have their own advantages and disadvantages. The final decision about a method’s applicability should be made following careful development and engineering work, including theoretical studies, modelling, laboratory testing, taking into account the available funds and logistics opportunities.

Deep Antarctic subglacial lakes represent physically unexplored aquatic environments, the investigation of which may provide unique information about microbial evolution, past climate of the Earth, and formation of the Antarctic ice sheet. Subglacial Lake Qilin identified in the middle part of the Princess Elizabeth Land is recognized as one of the ideal lakes for upcoming exploration. Currently, R&D work to develop a deep hot water drilling system to access this lake has been started in China, and the paper presents a general concept of the system and the brief description of the drilling strategy. Access drilling to the lake is planned for the season 2026/27.

The present buildings of the Russian station Vostok (East Antarctica) began to operate in 1963 and have been under snow for many years. In connection with the extensive plans to study the subglacial Lake Vostok, it was decided to build a new wintering complex. Since there is a thick snow-firn layer in the construction area, the building of the complex requires solid foundations measuring 200×120 m. It was decided to build them by means of layer-by-layer snow compaction. Based on the approximate weight of the complex of 2500 tons, its operation time of about 30 years, and the estimated pressure of the station supports on the snow cover of 100 kPa, the foundations slab must have a density of at least 550 kg/m³, and the hardness of the coating of more than 0.5 MPa. In developing the methodology of constructing the slab for the new wintering complex, the method of layer-by-layer snow compaction was taken as the basis, developed for the construction of airfields on deep snow and suitable for taking heavy aircraft on wheeled landing gear. Experimental snow compaction was carried out using various caterpillar tracks, after which stamp tests of snow surfaces with different initial snow characteristics were performed. The bearing capacity of the foundations was assessed by calculating the vertical mechanical stresses on their lower surface, which are formed by the pressure of the station supports. The strength characteristics of the snow were assessed by direct measurements using the Brinell method and with the help of a mechanical press based on the samples taken and a penetrometer. Ultimately, the density of the snow layers in the upper part of the foundations reached 650 kg/m³. In addition to the base layer, 9 additional layers were formed. The first eight were formed in the summer of 2019/20, and the last one in January 2022. The total thickness of the foundations exceeded 3 metres. Upon their construction, the average surface excess relative to the natural snow cover was 210 cm. Based on the rate of snow accumulation, as well as the subsidence of the station supports and foundations into the snow mass, the foundations surface will equal the level of natural snow cover in approximately 30 years.

The implementation of drilling projects in Antarctica requires comprehensive research and development work to study the processes of interaction between drilling equipment and ice and test devices designed for ice drilling. Testing facilities with artificial ice are essential for conducting this type of research. The article presents an analysis of the existing experimental stand projects, which identified a common drawback — inability to recreate a structure of atmospheric ice and thermobaric conditions similar to those in boreholes drilled in Antarctica. The authors propose the conceptual project of a сenter for testing technologies and technical devices for glacier drilling. The сenter is to be located on two sites: the first — on the “Sablino” educational and scientific testing ground of Saint-Petersburg Mining University in the Leningrad Region (Russia), the second — at the drilling complex of 5G borehole at Vostok station in Antarctica. The implementation of the project will allow conducting experimental research and testing, using both shallow artificial ice wells and deep boreholes in the Antarctic glacier. In addition, it will allow maintaining the drilling complex and 5G borehole in a good technical condition.

The research aimed to search for microbial life in subglacial Lake Vostok. This was done by examining the uppermost layer of water that entered the borehole and froze after the lake was accessed. The sample was collected from a depth of 3721 m and consisted of water-frozen re-cored ice. It underwent thorough decontamination and was melted successively in cold and cleanroom facilities. Genomic DNA was then isolated and amplified using v3-v4 16S rRNA bacterial gene region-specific degenerate primers. The Sanger method and high-throughput Oxford Nanopore sequencing were used to sequence the amplicons generated. The Sanger DNA analysis revealed 16 bacterial phylotypes, and only one of them, 3721v34-24, met all the contamination criteria. This phylotype was the dominant one, making up 41.4 % of the clones and consisting of three allelic variants. However, it remained unclassified and showed 87.7 % similarity to the closest GenBank entry, Mucilaginibacter daejeonensis NR_041505 of Bacteroidota (family Sphingobacteriaceae). The Oxford Nanopore technology generated 21067 reads for the 3721m sample and 3780 for the control one. Among these, 7203 (34 %) and 1988 (53 %) reads for the ice sample and the control one were classified with 93 % accuracy. For the 3721m sample, 21 bacterial phylotypes were identified with an abundance above 0.5 %. Fifteen were identical to the Sanger findings and identified as contaminants. The remaining six were different, either found in the control Nanopore trial or were apparent contaminants. The discovery of phylotype 3721v34-24 in the lake water by Sanger sequencing was unexpected. However, it was later detected in the 3721m sample and control experiments using nanopore sequencing, indicating it was also a contaminant. Thus, the research suggests that the topmost water layer in Lake Vostok may not contain any microbial DNA. Additional frozen-water samples are currently being analyzed to investigate the issue further.