Researchers have found evidence of an existing body of liquid water on Mars.
Just a mile or so beneath the surface, near the south pole of Mars, there is a reservoir of briny water sloshing and churning below layers of ice and rock.
This sub-glacial lake, discovered by a ground-penetrating radar on the Mars Express spacecraft, is about 20 kilometres (12.4 miles) wide and perhaps no more than a meter deep. Its discovery is the latest piece of evidence that suggests water was not only present on Mars in the past but is still flowing in some capacity today. The findings, if confirmed by future observations, would be the most significant discovery of liquid water on Mars to date.
Previous research found possible signs of intermittent liquid water flowing on the martian surface, but this is the first sign of a persistent body of water on the planet in the present day.
Scientists already had little doubt that there was, at one point, liquid water on Mars, thanks to tiny spherical deposits discovered by the Opportunity rover in 2004 and the comprehensive mineralogy studies conducted by the Curiosity rover. The evidence suggests that vast lakes and rivers dominated the surface of Mars billions of years ago. What's more, tantalising clues have continued to imply the existence of liquid water on Mars today. Condensation was measured on the Phoenix lander in 2009, and dark streaks spotted on Martian dunes may be evidence of briny water (although more recent examination suggests they could be avalanches of dry sand).
Artists impression: Marsis data shows an area of high reflectivity (dark blue) which is thought to be water
This new discovery of a subterranean water deposit, outlined in a new paper in Science,suggests water is indeed underneath the red sands of Mars. Maybe the Red Planet has entire subsurface lake systems like those beneath Antarctica.
The discovery was made using Marsis, a radar instrument on board the Mars Express orbiter.
"It's probably not a very large lake," says Prof Roberto Orosei from the Italian National Institute for Astrophysics, who led the study.
Marsis wasn't able to determine how deep the layer of water might be, but the research team estimate that it is a minimum of one metre.
"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," Prof Orosei added.
The study says the subglacial lake on Mars is cold indeed, and rather salty. Water ice that is near the melting point is opaque to radio waves, and so the ice above the lake must be well below freezing. The subglacial water must be at least negative 10 degrees Celsius.
A) Shaded relief map of Planum Australe, Mars, south of 75°S latitude. The black square outlines the study area. (B) Mosaic produced using infrared observations by the THEMIS (Thermal Emission Imaging System) camera, corresponding to the black square in (A). South is up in the image. The red line marks the ground track of orbit. The area consists mostly of featureless plains, except for a few large asymmetric polar scarps near the bottom right of (B), which suggest an outward sliding of the polar deposits (34).
For this to be possible, the reservoir must be saturated with salts—likely salts of sodium, magnesium, and calcium, which have been discovered on the Martian surface. These salts can reduce the melting point of water to negative 74 degrees C, so the subglacial lake is likely between this temperature and around negative 10 or 20 degrees.
"From what I think we have learned about this subglacial lake, the most likely analogue for this environment is the subglacial lake that was recently discovered in Canada... in which the lake itself is in contact with a deposit of salt, and so it is very very salty," Orosei says.
Such subglacial lakes on Earth have been shown to support life in some cases. "There are microorganisms that are capable of surviving well below zero even without being in contact with water, and there are microorganisms that can use the salt, presumably the salt in the water on Mars... for their metabolism."
The most intriguing possibility is that this Martian lake is not alone, but rather part of an extensive network expanding across the south polar region of Mars. “Data provide some hints that this single lake is not a unique finding," Orosei says. "We do see bright spots in other areas." MARSIS, however, does not have the technological capability to look for channels or rivers connecting a system of lakes.
Whether life could survive in Mars’ south polar lake—which is yet unnamed—is a decidedly iffier matter. On Earth, salty ocean water can remain liquid down to temperatures of just over 2º C. In the Martian lake, with its overlying pressure and its rich mineral mixture, the water could be as cold as -74º C. That’s an awfully frigid environment in which to try to make a biological go of things.
Still, life on Earth has been found in some pretty punishing places: in the interior of desert rocks, in the scalding hot springs of Yellowstone National Park, in Siberian permafrost. Compared to that, a little Martian ice water doesn’t seem so bad.
Ultimately, Mars may well turn out to be an entirely dead world. But for now, the question remains very much an open one—and thanks to the new study, researchers now have more places than ever to look for a hint of a Martian pulse.
Source: DOI: 10.1126 Radar evidence of subglacial liquid water on Mars