Call them the lakes that shouldn’t be.

Deep beneath a massive glacier in the Canadian Arctic, scientists have discovered a pair of hidden reservoirs that may offer a unique opportunity for testing the possibility that life exists elsewhere in our solar system.

The lakes, which were discovered with the help of ice-penetrating radar, measure eight and five kilometres long and occupy parallel depressions on Nunavut’s Devon Island. They lie beneath the centre of a sprawling, permanent ice cap that covers the eastern end of the island. Scientists estimate the ice cap has kept the lakes sealed off from their surrounding environment for up to 120,000 years.

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But what is most surprising about the lakes is how cold they are. Calculations suggest they must be at or near -10.5°C. Only extremely briny water – about 15 per cent salt by weight – can remain liquid at such a low temperature. This offers the prospect of two dark, cold, hypersaline bodies of water that may be the closest thing Earth has to what exist under the ice caps of Mars or the hidden ocean of Jupiter’s moon Europa.

“They might be a unique ecosystem that could support microbial life,” said Anja Rutishauser, a PhD student at the the University of Alberta, who made the discovery. “This might help us better understand the possibilities and limitations of life in such extreme environments on Earth, but also beyond Earth.”

Ms. Rutishauser spotted the lakes last year while examining radar cross-sections through the Devon ice cap obtained from NASA and other U.S. collaborators. They appeared then as two flat-bottomed troughs, dubbed T1 and T2, with highly reflective surfaces that are typical of bodies of water hidden by ice.

“I wasn’t looking for lakes. We didn’t think there was liquid water there at all,” she said.

Ms. Rutishauser and colleagues later worked out that a geological layer with salt-bearing minerals discovered elsewhere on Devon Island is likely to break the surface at the point where the lakes are situated. Contact between the salt and the bottom of the ice cap may thus have produced a briny slush or perhaps stretches of more open salt water under an icy lid.

The radar data do not show how deep the lakes may be or what volume of water they contain.

The find, reported Wednesday in the journal Science Advances, marks the first time that subglacial lakes have been detected in Canada. The unusual properties of the lakes appear to make them unlike any in the world.

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While there are known to be about 400 lakes under the Antarctic ice sheet and a handful more in Greenland, they are freshwater bodies kept fluid by pressure or fed by meltwater from above. None are thought to be as cold or as salty as the lakes on Devon Island.

“This is big. We’ve got a little jewel here now that’s going to attract a lot of attention in terms of planetary science,” said Lyle Whyte, a microbiologist at McGill University in Montreal who specializes in life under extreme conditions and was not involved in the discovery.

Dr. Whyte added that getting through the 740-metre thick ice cap to sample whether anything is living in the lakes there would be “a major undertaking,” but one that many scientists would be keen to try.

Life in the lakes would have to contend with the absence of sunlight and a severe shortage of organic carbon, Dr. Whyte said. Any microbes surviving there would be forced to derive their energy from chemical reactions rather than photosynthesis.

“The bugs would have to be eating rocks,” he said.

Bacteria have been discovered doing similar things deep in the Earth and in other extreme locations such as hot springs and deep sea vents. But no one has examined an environment quite like the one the Devon Island lakes may present, which would likely have several factors in common with watery locales elsewhere in the solar system.

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Mark Skidmore, a geologist at Montana State University who was a collaborator on the find, has previously been involved in sampling subglacial lakes under the Antarctic ice sheet using hot water drills. The low temperature at the base of the Devon Island glacier would likely require a modified version of the technology, he said.

“One potential solution would be to use a highly saline solution as the drilling fluid, so that it would not freeze in the borehole during the drilling process,” he said.

Dr. Skidmore added that measures could be taken to avoid contaminating the lakes with bacteria from the surface.

Laying the groundwork for such an effort would be a multiyear undertaking.

Ms. Rutishauser said the next step will come in May, when she and others will head to Devon Island to gather more radar data and better characterize the lakes.

As for what the lakes should be called, “We have not thought about naming these lakes, and I am not sure who would get to name them,” Ms. Rutishauser said. “To me, it would make sense to give them an Inuit name.”