Lake Vostok
The Lake Vostok (Russian: Озеро Восток, romanization Ozero Vostok, literally Lake of the East ) is the largest of the nearly 400 known subglacial lakes in Antarctica. The lake is located at the so-called cold pole, located below the Russian Vostok base, some 3,748 m from the surface of the East Antarctic ice sheet, isolated from the outside and protected from the atmosphere. The surface of this freshwater lake is approximately 4,000 m below the ice surface, which puts it about 500 m below sea level. It measures 250 km long by 50 km wide at its widest, and covers an area of 12,500 km² and an average depth of 432 m. It has an estimated volume of 5,400 km³. The lake is divided into two deep basins by a ridge. Liquid water on the ridge is about 200 m deep, compared to almost 400 m in the northern basin and 800 m deep in the southern one.
The name of the lake comes from the Vostok scientific base, which itself is named after a ship, the corvette Vostok (Восток), which means "east" or "east" in Russian The existence of a subglacial lake in the Vostok region was first suggested by the Russian geographer Andrei Kapitsa, based on seismic surveys carried out during the Soviet Antarctic expeditions between 1959 and 1964 to measure the thickness of the ice sheet. Subsequent research conducted in 1993 by Russian and British scientists led to definitive confirmation of the lake's existence by J. P. Ridley, using the ERS-1 laser altimeter. The ice covering the surface provides a continuous paleoclimate record of 400,000 years, although the lake's own body of water may have been isolated 15 to 25 years ago. million years ago. On February 5, 2012, a team of Russian scientists extracted the longest ice core to date, at 3,768 m, and drilled through the ice shield on the lake's surface.
The first sample of freshly frozen water was obtained on January 10, 2013, at a depth of 3,406 m. But, as soon as the ice sheet was pierced, water from the underlying lake gushed out of the well and it mixed with the freon and kerosene used to keep the well cool. In January 2015, a new "clean" well was drilled and a sample of supposedly virgin water was obtained. The Russian team planned to lower a probe into the lake to collect water and sediment samples from the bottom. The team's hypothesis is that unusual forms of life could be found in the liquid layer of the lake, a reservoir of fossil water. The lake contains an environment sealed under ice for millions of years, in conditions likely resembling those of the ice-covered ocean on Jupiter's moon Europa or Saturn's Enceladus.
Discovery
Russian scientist Pyotr Kropotkin was the first to propose the existence of fresh water under the Antarctic ice sheets in the late 19th century. He theorized that the enormous pressure exerted by the accumulated mass of thousands of meters of ice it could increase the temperature in the lower parts of the ice sheet to the point where it would melt. Kropotkin's theory was developed by the Russian glaciologist I. A. Zotikov, who wrote his doctoral thesis on this topic in 1967.
Russian geographer Andrei Kapitsa used seismic surveys in the area of the Vostok station, built during the Soviet Antarctic Expedition between 1959 and 1964, to measure the thickness of the ice sheet. Kapitsa was the first to suggest the existence of a subglacial lake in the region, and further research confirmed his hypothesis.
In the early 1970s, British scientists conducted aerial surveys with ice-penetrating radar and detected unusual readings at a site that suggested the presence of a liquid freshwater lake beneath the ice sheet. In 1991, Jeff Ridley, a remote sensing specialist at University College London's Mullard Space Science Laboratory, directed the ERS-1 satellite to shoot a high-frequency beam toward the center of the Antarctic ice sheet. The ERS-1 data confirmed the findings of the 1973 British survey, but these new data were not published in the Journal of Glaciology until 1993. Space-based radar revealed that this subglacial body of water Dulce is one of the largest lakes in the world, and one of some 140 subglacial lakes in Antarctica. In 1996, a group of Russian and British scientists mapped out the lake by integrating a variety of data, such as observations from an airborne ice-penetrating radar and spaceborne radar altimetry. The lake was confirmed to contain large amounts of liquid water under a layer of ice more than 3 km thick. The lake has at least twenty-two cavities of liquid water, each 10 km on average.
The name of the lake comes from the Vostok base, which itself is named after a 900-ton sloop-of-war ship, the Vostok (Восток), commanded by one of the discoverers of Antarctica, Russian admiral and explorer Fabian Gottlieb von Bellingshausen. The word Bосток means "east" or "east" in Russian, and the name of the station and lake refer to the fact that they are located on the eastern part of the continent. In 2005, an island was found in the center of the lake. Later, in January 2006, the discovery of two smaller nearby lakes under the ice sheet was published; they are named 90°E (90 Degrees East) and Sovetskaya. It is suspected that these lakes may be connected by a network of subglacial rivers. Glaciologists from the Center for Polar Observation and Modeling have proposed that many of the subglacial lakes in Antarctica are at least temporarily interconnected. Due to variation in Due to the water pressure between individual lakes, large underground rivers can suddenly form and then force large volumes of water through solid ice.
The water it contains is very old, with an average residence time of one million years, which contrasts with Lake Ontario's six years. This means that the same water molecule takes time to renew itself and leave the around an average of one million years, a renewal rate much lower than that of common lakes (50 to 100 years) and even that of oceanic masses (about 3,200 years), compared to that of subsoil water is renewed hundred times faster (10,000 years).
Geological history
Africa separated from Antarctica about 160 million years ago, followed by the Indian subcontinent in the Early Cretaceous (about 125 million years ago). About 66 million years ago, Antarctica (then connected to Australia) had a tropical or subtropical climate, a marsupial fauna, and extensive temperate rainforest.
The lake basin is small (50 km wide) and with tectonic features within a 100 km zone of several continental collisions between the Gamburtsev Ridge, a subglacial ridge, and the C Dome region. It is housed in a 70 m thick bed of sediment, which offers the possibility of containing a unique climate record and life in Antarctica before the ice sheet formed.
Features
The water in the lake is estimated to have been sealed under a thick layer of ice about 15 million years ago. residence of about a million years. However, subsequent research by Robin Bell and Michael Studinger (of Columbia University's Lamont-Doherty Earth Observatory) concluded that the lake's water is continuously frozen and is left carried away by the movement of the Antarctic ice sheet, although it is replaced by melt water from other parts of the ice sheet under high pressure conditions. Based on this, it is estimated that the entire volume of the lake is replaced every 13,300 years—an average residence time.
The coldest temperature recorded on Earth, -89 °C, was recorded at the Vostok base on July 21, 1983. As for the reasons why it remains liquid in the coldest place on the planet, they have been suggested various hypotheses. The first ensures that the average temperature of the water would be -3 °C; It remains liquid below the normal freezing point due to the high pressure (360 atm) caused by the weight of the ice on top of it. Its solidification is not possible (at that temperature), since the ice melts under pressure. The second theory states that geothermal heat from the interior of the Earth warms the rocks under the lake, or that the ice cover, Being a poor conductor of heat, it could act as an insulating blanket, protecting it from cold surface temperatures. Another possibility is that the lake did not have time to freeze after a warm period that ended around 5,000 years ago..
The lake is an extreme oligotrophic environment, and is expected to be supersaturated with nitrogen and oxygen, with about 2.5 L of nitrogen and oxygen per 1 kg of water, meaning fifty times higher concentrations than those normally found in ordinary freshwater lakes on the earth's surface. The weight and absolute pressure are estimated to be as high as 345 bar on the continental ice sheet above the lake; this contributes to the high concentration of gas. Apart from dissolving in water, oxygen and other gases are trapped in a type of structure called clathrate. In these structures, the gases are enclosed in an icy cage and are observed as packed snow. These form deep in the lake at high pressure and would be unstable if they reached the surface.
In April 2005, German, Russian and Japanese researchers discovered that the lake is also tidal. Depending on the position of the Sun and Moon, the surface rises by 12 mm. The lake is in total darkness, at a pressure of 355 bars and with an environment rich in oxygen, so the researchers speculate that the organisms that inhabit the lake could have evolved in a unique way and that the fluctuation of the surface has the effect of a pump that it keeps water circulating. Starting in 2001, a group of American scientists began flying low over Lake Vostok to study its magnetic activity. During these flybys, a powerful 1 µT magnetic anomaly was discovered at the eastern end of the lake, spanning 105 x 75 km. The researchers hypothesize that the anomaly could be caused by a thinning of the Earth's crust at that location.
Some microorganisms, such as Hydrogenophilus thermoluteolus, have been found living in ice cores extracted from the depths; they are species that reside only on these surfaces. In line with the above, scholars suggest the presence of a deep biosphere inhabiting a geothermal system in the bedrock surrounding the subglacial lake. They also propose that it is possible for microbial life to exist in the lake despite the high pressure, the constant cold, the low nutritional supply, the potentially high concentration of oxygen and the absence of sunlight. In this sense, Europe, a moon of Jupiter, and Enceladus of Saturn could harbor lakes or oceans under a thick layer of ice. The possibility of life inside Lake Vostok could reinforce the theory of the presence of life on natural icy satellites.
Investigations
In 1998, researchers at the Vostok base produced one of the longest ice cores in the world. A team of Russians, French and Americans drilled and analyzed the 3,623m long core. They found that ice cores from drilling near the top of the lake could be as old as 420,000 years. In the proposed theory is that the surface of the lake was sealed by the formation of an ice sheet layer, 15 million years ago. Core drilling was deliberately stopped near 100 m from the supposed boundary between the ice sheet and the liquid waters of the lake. This was done to prevent contamination of the lake with a 60-ton column of freon and the kerosene used to prevent the pit would collapse and freeze it again. The deepest part of this ice-formed core is believed to have originated from frozen lake water at the base of the ice sheet; extremophile microbes were found in that area, indicating that the lake water is compatible with life forms. Scientists suggested that the lake might possess a unique habitat for ancient bacteria with an isolated microbial gene pool containing features possibly developed as early as 500,000 years ago. The lake is known to consist of two trenches separated by a ridge, therefore that researchers theorize that the chemical and biological compositions of the two could be different.
When it snows, air is trapped in the flakes; at the poles and in other regions perpetual snow ends up forming ice. The air is trapped in small bubbles. Normally 100 ml are trapped in each kilogram of ice. of air. In this way, the polar ice functions as an "air museum", providing information on the composition of the atmosphere up to half a million years ago. Gas extraction and analysis techniques provide CO2 concentrations prior to the present moment and provide evidence of climate change. Ice records show that CO2 concentrations are unprecedented in the last 650,000 years.
In January 2011, the head of the Russian Antarctic Expedition, Valery Lukin, announced that his team had only 100m of ice left to drill to reach the lake water. The researchers swapped out a thermal drill head for a new one with a "clean" silicone oil fluid to drill the remainder of the tunnel. Rather than drill to find the water, they stopped just as a sensor on the thermal drill detected free water. At that point, the drill was slowed down and withdrawn from the drill hole. Withdrawing the bit would reduce the pressure beneath it, causing water to enter the hole, freeze, and create an ice plug at the bottom of the hole. Drilling was stopped on 5 February 2011 at a depth of 3,720 m, so the research team was able to extract the ice before the start of the Antarctic winter season. The rig was airlifted on February 6, 2011.
According to plan, the team returned the following summer to take a sample of the ice for analysis. The Russians resumed drilling on the lake in January 2012, reaching the upper surface of the water on the 6th. February 2012. The researchers allowed the lake water to freeze inside the borehole and, months later, collected core samples from this newly formed ice and sent them to the Laboratory for Glaciology and Environmental Geophysics in Grenoble for analysis..
Results of biological studies
British and American researchers
Scientists reported evidence of microbes in accretion ice in 1999. Since then, a team led by Scott O. Rogers has identified a variety of bacteria and fungi in accretion ice (not from the subglacial water layer).) collected during US drilling projects in the 1990s. According to Rogers, this indicates that the lake under the ice sheet is not barren, but instead contains a unique ecosystem. Rogers published in July 2013 an article about the experiments that his team carried out to obtain the sequencing of nucleic acids (DNA and RNA) and the results made it possible to deduce the metabolic pathways represented in the accretionary ice and, by extension, in the ice. lake. The team found 3,507 unique gene sequences, with approximately 94% of the sequences being from bacteria and 6% from eukaryotes. Taxonomic (genus and/or species) classifications or identifications were possible for 1,623 of the sequences.. In general, the taxa were similar to previously described organisms in lakes, brackish waters, marine environments, soils, glaciers, ice, lake sediments, deep-sea sediments, deep-sea hydrothermal vents, animals, and plants, among others. Sequences of aerobic, anaerobic, psychrophilic, thermophilic, halophilic, alkaliphilic, acidophilic, desiccation resistant, autotrophic and heterotrophic organisms were present, including a number of multicellular eukaryotes.
However, microbiologist David Pearce, from Northumbria University in Newcastle upon Tyne, suggested that the suspected DNA could simply be contamination from the drilling process, and is not representative of Lake Vostok itself. The ancient ice cores drilled in the 1990s were to look for evidence of prehistoric climate buried in the ice, rather than traces of life, so the drill team did not sterilize them. Also Sergey Bulat, a lake expert at the Institute of St. Petersburg Nuclear Physics in Gatchina, doubts that any of the cells or DNA fragments in the samples could belong to organisms that might exist in the lake. He says it's very likely that the samples are heavily contaminated with tissue and microbes from the outside world.
Russian and French researchers
Russian and French scientists have carried out molecular DNA studies of the lake water that was frozen at the well, by building numerous gene libraries, which are snippets of DNA that allow scientists to identify which species of bacteria they can belong So far, samples taken from the lake contain approximately one part kerosene per 1,000 water, and are contaminated with bacteria previously present in the drill bit and kerosene in the drilling fluid. So far, scientists have been able to identify 255 contaminating species., but they have also found an unknown bacterium when the surface of the lake was drilled in 2012; the taxon does not match other species in international libraries and is expected to be a unique inhabitant of Lake Vostok. However, Vladimar Korolev, the study's laboratory head at the same institution, said the bacteria could be, in principle, a contaminant that uses kerosene—the antifreeze used during drilling—as a power source.
The scientific community indicated that no valuable information will be obtained until they can provide clean samples of lake water, uncontaminated by the drilling fluid. In May 2013, the drilling facility at the Vostok base of the Antarctica was declared a historical monument as "the result of the recognition of the achievements of the Russian Antarctic research by the international scientific community, and of the independent operations to open the subglacial Lake Vostok, carried out by Russian scientists on February 5, 2012.", regardless of contamination problems. In January 2015, Russia Today claimed that Russian scientists had made a new "clean" well in the lake using a special 50 kg probe, which collected approximately 1 L of water uncontaminated by the antifreeze fluid. The water would rise 30-40 m at the bottom of the drilling hole, but in reality the water rose to a height of more than 500 m. In October 2015, the work was suspended due to the austral summer and due to low Funding provided by the Russian federal government.
Recent research and access to the lake
Some environmental groups oppose the drilling project, and some scientists have argued that hot-water drilling would have a more limited environmental impact. open the well. Scientists from the US National Research Council advise that it should be assumed that microbial life exists in Lake Vostok, and that after long isolation, any life in its waters requires strict protection against contamination.
The original drilling technique, employed by the Russians, involved the use of Freon and kerosene to lubricate the drilling and prevent it from collapsing and freezing before completion; so far, 60 short tons of these chemicals have been used on the ice on the lake. Other countries, notably the United States and the United Kingdom, have failed to convince the Russians not to continue drilling the lake until use cleaner technologies, such as hot water drilling. Although the Russians claim to have improved their operations, they are still using the same borehole, which is contaminated with kerosene. According to Lukin, new equipment developed by Institute researchers of Nuclear Physics in Saint Petersburg would make it possible to ensure that the research did not cause contamination of the lake. It was the Saint Petersburg Mining Institute that developed a type of probe based on pressure variation, acting like a plunger that sucks water up from the lake Lukin repeatedly assured that other nations signatory to the Treaty System Antarctic can drill into the lake without affecting it, arguing that opening the hole will cause water to rush into the well, freezing and neutralizing nearby chemical fluids.
To prove the existence of life in Lake Vostok without polluting the environment in the process, NASA's Jet Propulsion Laboratory (JPL) planned to use an ice-melting probe called a "cryobot" that it would melt the ice in its wake, leaving behind a communications and electrical power cable. The cryobot would carry with it a mini-submarine called a "hydrobot", which will be deployed once the cryobot has melted the ice and reached the waters of the lake. The mission of the hydrobot would be to search for the existence of life in the lake waters, using a video camera and other measuring instruments.