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By David Freeman

A large reservoir of liquid water has been found deep beneath the frozen surface of Mars near the planet’s south pole, according to a new paper by Italian researchers published in the journal Science.

The discovery caps decades of debate over whether such bodies of liquid water exist on Mars today and is sure to fuel speculation about the possibility that life exists on the Red Planet. Water is considered an essential ingredient for life.

Mars' south polar ice cap in an image captured the European Space Agency's Mars Express spacecraft. Italian researchers believe a reservoir lies below ice about a mile thick in an area close to the planet's south pole.ESA

“I think the chances now of finding a place to look for current life have gone up,” said Scott Hubbard, a professor of astronautics at Stanford University in Stanford, California, who was not involved in the new research. Hubbard, who served as NASA's first Mars program director, called the discovery “thrilling and exciting.”

The subglacial lake was detected below a polar region known as Planum Australe by a ground-penetrating radar instrument aboard the European Space Agency’s Mars Express spacecraft, which has been orbiting Mars since 2003. The lake is about 20 kilometers (12 miles) wide and is buried about 1.5 kilometers (1 mile) below the surface, according to an analysis of radar readings made between 2012 and 2015.

ESA's Mars Express used radar signals bounced through underground layers of ice to identify a pond of water buried below the surface.ESA

“This is just one small study area,” Roberto Orosei, an astronomer at the University of Bologna and the study’s lead author, said in a written statement. “It is an exciting prospect to think there could be more of these underground pockets of water elsewhere, yet to be discovered.”

The newfound lake is likely to be extremely cold and salty, according to the research. Those are “not ideal conditions for life to form,” Kirsten Siebach, a planetary scientist at Rice University in Houston, told the Associated Press. But, she added, microbial life has been found in such environments on Earth.

Among other extreme environments on our planet, microbes have been found in Lake Vostok, a large subglacial lake in Antarctica.

Scientists have long believed that water flowed on Mars billions of years ago, when the planet was hotter, and it's well-established that large deposits of water ice exist there still. Recent research showed that complex organic molecules — the building blocks of life as we know it — are present there. But this is the first time a stable body of liquid water has been detected on Mars.

The Italian scientists spent years analyzing the data to make sure the radar readings indicated liquid water — but not everyone is convinced.

“I would say the interpretation is plausible, but it’s not quite a slam dunk yet," Jeffrey Plaut, a research scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California, who is not involved in the new research, told Science.

But Hubbard called the researchers a “careful group” and said he found the new research convincing — and a likely prelude to additional research. “I think this finding will stimulate other science groups" to reexamine radar data of Mars "to see if they missed anything."

Additional reporting by Denise Chow

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