Liquid Water Lake Detected Beneath the South Polar Ice Cap of Mars

Researchers have detected the presence of a body of water in liquid form below the ice-layered surface of the Mars’ south polar region | they say the water is likely too brackish to have supported life

Liquid Water Lake Detected Beneath the South Polar Ice Cap of Mars

Researchers at the Italian Space Agency have discovered evidence of liquid water under the desolate, inhospitable surface of Mars.

Published Wednesday (July 25) in the journal Science, the findings of the new study point toward the possible existence of a lake of liquid water beneath the red planet’s south polar ice cap.

The evidence, however, cannot be called conclusive by any stretch of the imagination until further research gives absolute credence to the discovery.

The data was collected with the help of an instrument called the Mars Advanced Radar for Subsurface and Ionosphere Sounding, better known by its acronym MARSIS, onboard the European Space Agency’s Mars Express spacecraft.

Probing the Planum Australe – the southern polar plain of Mars – between May 2012 and December 2015, MARSIS was able to compile radar profiles that were found to contain evidence of a body of liquid water trapped less than a mile (1.5 kilometers) below the ice-capped surface, stretching laterally for about 12 miles, or 20 kilometers.

While the MARSIS data didn’t help in determining the vertical depth of the subsurface water layer, the researchers do estimate it to be at least one meter thick.

The MARSIS modus operandi was to send out low-frequency radar signals to the surface and immediate subsurface of the Planum Australe region of the planet, enabling the research team to study the signals that were bounced back to Mars Express.

In the illustration below, you will notice a steady white line at the top, which indicates the starting point of the South Polar Layered Deposit (SPLD), which is nothing but a build up of ice and Martian dust.

Just short of a mile below the SPLD is where the researchers detected the evidence of the meter-deep, 20km-wide layer of liquid water.

“In light blue you can see where the reflections from the bottom are stronger than surface reflection. This is something that is to us the tell tale sign of the presence of water,” says Prof Roberto Orosei from the Italian National Institute for Astrophysics, who is also the head of the research team and lead author of the study paper.

Artists’ impression of ESA’s Mars Express probing the planet’s surface, with the radar findings on top (source: ESA/INAF)
Artists’ impression of ESA’s Mars Express probing the planet’s surface, with the radar findings on top (source: ESA/INAF)

“It’s probably not a very large lake,” Orosei said.

“This really qualifies this as a body of water. A lake, not some kind of meltwater filling some space between rock and ice, as happens in certain glaciers on Earth,” added the professor.

If the study authors’ interpretation of the findings is indeed what they say it is, then we‘re likely looking at the first known stable body of liquid water on the mysterious planet.

“Anomalously bright subsurface reflections are evident within a well-defined, 20-kilometer-wide zone centered at 193°E, 81°S, which is surrounded by much less reflective areas,” says the ‘Abstract’ of the study paper.

“Quantitative analysis of the radar signals shows that this bright feature has high relative dielectic permittivity (>15), matching that of water-bearing materials. We interpret this feature as a stable body of liquid water on Mars,” it said.

The authors strongly believe in the possibility of more such water bodies lying hidden beneath the Martian surface, based on the simple logic that they haven’t found any evidence that suggests otherwise.

“There is no reason to conclude that the presence of subsurface water on Mars is limited to a single location,” they wrote.

Orsei is also upbeat about the possible presence of more such subsurface water reservoirs on the planet.

“This is just one small study area,” Orosei said in a statement. “It is an exciting prospect to think there could be more of these underground pockets of water elsewhere, yet to be discovered.”

“We have long since known that the surface of Mars is inhospitable to life as we know it, so the search for life on Mars is now in the subsurface,” said Dr. Manish Patel, as quoted by BBC Science reporter Mary Halton in her July 25 piece on the study.

“This is where we get sufficient protection from harmful radiation, and the pressure and temperature rise to more favorable levels. Most importantly, this allows liquid water, essential for life,” Dr. Patel is believed to have said.

“We are not closer to actually detecting life but what this finding does is give us the location of where to look on Mars,” Dr. Patel told BBC News, comparing it to a treasure map, “except in this case, there will be lots of ‘X’s marking the spots.”

For water to remain in liquid form in temperatures that the researchers estimate is somewhere between -10 and -30 Celsius, the water is likely to be highly saline, which basically means it was, probably, never conducive to any kind of life form.

“It’s plausible that the water may be an extremely cold, concentrated brine, which would be pretty challenging for life,” said Dr. Claire Cousins, an astrobiologist from the University of St Andrews, UK – again, quoted by BBC.

Talking about life on Mars, early last month, NASA announced that its nuclear-powered Curiosity rover had discovered organic matter embedded in the sedimentary rocks of the three-billion-year-old Gale Crater on the planet.

The organic molecules found in the ancient bedrock suggested that conditions back then may have been ideal to support some form of life, with a good chance that microorganisms once thrived on the red planet.

Regardless of the origin of the organics, their presence itself meant that they were a good source of food for any microbes that may have existed back then.

“We know that on Earth microorganisms eat all sorts of organics. It’s a valuable food source for them,” Jennifer Eigenbrode – a NASA biogeochemist and geologist with expertise in organic and isotope biogeochemistry and interests in astrobiology had said at the time.

“While we don’t know the source of the material, the amazing consistency of the results makes me think we have a slam-dunk signal for organics on Mars,” she said.

“It is not telling us that life was there, but it is saying that everything organisms really needed to live in that kind of environment, all of that was there,” added Eigenbrode.

Curiosity’s findings revealed that, way back in the past, a liquid water lake inside the Gale Crater had all the necessary building blocks to sustain life in one form or another.

“The Martian surface is exposed to radiation from space. Both radiation and harsh chemicals break down organic matter,” Eigenbrode said.

“Finding ancient organic molecules in the top five centimeters of rock that was deposited when Mars may have been habitable, bodes well for us to learn the story of organic molecules on Mars with future missions that will drill deeper,” added the NASA biogeochemist.

So, while NASA’s Curiosity data hinted at the possibility of life having existed on Mars at some point in the dim and distant past, MARSIS’s findings suggest that conditions were not that friendly – at least, in so far as the Planum Australe region of the planet is concerned.

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