A radar equipped probe has detected the first concrete evidence of existing liquid salty water on Mars, in the form of a large lake under one of its polar ice caps, raising the possibility of finding life on the red planet.
Lead researcher Roberto Orosei said it’s the closest his team can get to confirming that the lake is truly water, without drilling through a glacier to sample the reservoir.
“We discovered water on Mars,” Orosei said, in a video interview released with the study.
The discovery resolves a long-running debate over whether there is liquid water on Mars, according to the Italian Space Agency (ASI) researchers who ran the operation.
The lake is approximately 20 kilometres wide and sits 1.5 km below the Martian surface under a heavy polar glacier. It’s also extremely cold and filled with a briny mix of salt and other minerals, according to the study published in the latest edition of the journal Science.
The buried lake was first detected by a team of Italian astronomers using the Mars Express spacecraft, which surveyed the planet’s southern polar cap between May 2012 and December 2015.
The spacecraft used a ground-penetrating radar to scan the region and found a sharp contrast in the echo under a section of the glacier, which matched the profile of a subglacial lake.
The research team spent several years taking more scans and analyzing the data before announcing the findings to confirm the data.
“Any other explanation for these very strong echoes was not really tenable,” Orosei said.
“We had to conclude that there is water on Mars today.”
The suspected lake matches the radar profile of the liquid water reservoirs under glaciers in Antarctica and Greenland, according to the study.
The results appear to be scientifically sound, and reflect the same kind of scans that are produced by subglacial lakes on Earth, according to Anja Diez of the Norwegian Polar Institute.
“They rule out a number of possible explanations … leaving the existence of liquid water, either as a distinct water layer or as saturated sediments, as the only explanation,” she wrote in a commentary on the findings.
The researchers said it could take years to verify whether something is actually living in this body of water that resembles a subglacial lake on Earth, perhaps with a future mission drilling through the ice to sample the water below.
The prospect of water on Mars is enough to spark renewed talk of one day colonizing the Red Planet.
However, the underground reservoir isn’t exactly human friendly.
“This is certainly not a very pleasant environment for life,” Orosei said.
“This is the place on Mars where you have something that most resembles a habitat, a place where life could subsist,”
“This kind of environment is not exactly your ideal vacation, or a place where fish would swim,” Orosei added. “But there are terrestrial organisms that can survive and thrive, in fact, in similar environments. There are microorganisms on Earth that are capable of surviving even in ice.”
Orosei didn’t rule out the possibility of life altogether, as there are single-cell organisms that live in similar subglacial lakes on Earth.
Orosei said the water in the Martian lake was below the normal freezing point but remained liquid thanks in large part to high levels of salts. He estimates the water temperature to be somewhere between -10 and -30 C, though it’s probably still liquid because of dissolved salt, magnesium, calcium and sodium that would have leached into it from the Martian rock.
“Together with the pressure of the overlying ice, this lowers the melting point, allowing the lake to remain liquid,” the study authors say.
Orosei says the water is at least one metre deep, although scans are unable to determine exactly how deep it goes.
The lake sits under a glacier on the southern plain of Mars, known as the Planum Australe.
The lake was found in a relatively flat area where ground-penetrating radar scans are easier to read, ASI scientist Enrico Flamini said.