Frigid lakes locked under the Antarctic ice sheet may be home to microbiological life than scientists ever imagined.
More than 400 subglacial lakes lies below Antarctica ice cover, completely closed from sunlight, according to a new paper published Feb. 17 in the magazine Scientific progress. These lakes form where the weight of the surface ice drops to the bottom of the sheet, creating intense pressure and lowering the melting point of the ice. As the base melts, the remaining ice insulates the melt water from the cold air, while the geothermal heat from the bottom substrate also helps prevent freezing, according to the statement.
Some of these dark lakes lie near the edge of the ice sheet, where water can occasionally flow in and out. Scientists have discovered microbial life in two of these hydrologically active lakes, but it is not known whether isolated lakes near the center of the ice sheet can also sustain life. Many of these lakes have been cut off from the surrounding environment for millions of years.
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Past research has suggested that microorganisms in these forbidden lakes probably live in sediment at the bottom of the lake, full of nutritious minerals, a 2018 study from the journal Letters on Earth and Planetary Science found. But now, a new study suggests that microbes can thrive through the extreme ecosystem, both in sediment and in surrounding water.
Geothermal heat flow – the flow of heat from the Earth’s interior – basically stirs lake water, raising nutrients from sediment into the upper water, the study suggests.
“The water in the lakes isolated under the Antarctic ice sheet has not been calm and immobile for millions of years; the water flow is actually quite dynamic,” lead author Louis-Alexandre Couston, a physicist at the University of Lyon in France and the British Antarctic Research, said in a statement. “With dynamic water flow, the whole body of water can be habitable.”
In above-ground lakes, water flows due to wind and heat from the sun. This feeds convection currents, where differences in water temperature across the lake trigger water flow. Although subglacial lakes cannot be warmed by the sun, the team found that the heat from inside the planet is strong enough to drive “strong” convection currents from below. The heat itself is created by the decomposition of radioactive elements, such as thorium i uranium, and also includes heat left over from the time the Earth first formed, according to a 1990 report in the journal Geophysics.
As heat causes the circulation of subglacial water, this flow not only releases minerals from the sediment, but also distributes oxygen and minerals from the higher layers of water; these additional nutrients come from the dust trapped in the ice sheet that is released as the ice melts.
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“Our calculations show that mixing subglacial lake water is very likely and would encourage the spread of oxygen-rich water through the water column to the lake bottom sediments, where microbial life is probably most prevalent,” the authors wrote in a new study.
The team based these initial conclusions on modeling studies, but soon scientists plan to sample water and sediment from a subglacial lake called Lake CECs, named after the Chilean science center Centro de Estudios Científicos, the statement said. This expedition will allow the team to test their predictions and see where microbes actually live in a unique ecosystem.
For now, based on their current modeling, “it should be taken into account that most – if not all – of Antarctic subglacial lakes are a dynamic hydrological environment,” the authors wrote. “We expect the same conclusion to apply to isolated subglacial lakes in Greenland and elsewhere in Solar system, “relative to subglacial lakes on the moons Jupiter i Saturn, they added.
“The physics of subglacial water pockets are similar on Earth and the ice months, but the geophysical environment is quite different,” meaning the physical properties of the environment, study author Martin Siegert, co-director of the Grantham Institute – Climate Change and Environment at Imperial College London. in a statement. Thus, although both environments are similar, new theories will be needed to understand what additional physical factors could shape subglacial lakes on ice months, Siegart said.
“With new missions focused on the icy moons and increasing computing capabilities, it’s the right time for astrobiology and the search for life beyond Earth,” he said.
Originally posted on Live Science.