Saltwater lake discovered on Mars
There is a lake with several ponds under the south pole of the Red Planet
A hidden oasis of life? There is a large lake of liquid saltwater under the South Pole of Mars, as now confirmed by radar data from ESA's Mars Express probe. Accordingly, the subglacial lake is around 20 by 30 kilometres in size and surrounded by smaller pools. A high concentration of perchlorate salts probably keeps the water in the liquid, but the researchers speculate whether there is life in these lakes remains open.
Even if it doesn't seem like it, there is water on Mars. However, this occurs almost exclusively as water vapour or ice - for example in glaciers below the surface and in the ice caps of the Martian poles. But there could also be residual liquid water, according to the latest data from space probes and rovers. Evidence for this is perchlorate-containing alkalis in the Martian subsurface, which could at least temporarily be liquid.
Search for liquid water under the Marseis
Another reservoir of possibly liquid water could lie under the ice cap at Mars' South Pole. Data from the MARSIS radar sensor onboard the ESA Mars Express probe provided initial indications of this in 2018. The measurements showed a brightly reflective layer at the base of the thick ice shell. However, it was not clear from the data whether it was just water-saturated material or layers of liquid water.
Elena Pettinelli from the University of Roma Tre and her colleagues have now evaluated further data from the MARSIS instrument. Their analyzes are based on 134 radar profiles that the ESA spacecraft created between 2010 and 2019 in the Ultimi Scopuli region. This area is around 80 degrees south and is covered by an ice sheet a good kilometre thick. For their analyzes, the researchers modified a method with which several subglacial lakes on Greenland and Antarctica have already been found.
A large lake and many smaller pools
The results confirm: Under the thick south pole of Mars there is liquid water in the form of a subglacial lake. "The area is characterized by a large body of water that is surrounded by smaller pools of water or wetlands," report Pettinelli and her colleagues. The central lake has a diameter of 20 by 30 kilometres and appears to be stable and fluid. It is separated from the surrounding pools by narrow strips of dry rock.
How and why these lakes and ponds under the Marseis remain liquid is still unclear. “We can only speculate about the unique combination of physical, geological, climatic and topographical conditions that enable the formation and persistence of liquid water,” say the researchers.
However, they suspect that subglacial water resources contain high concentrations of perchlorate salts. This is because such brine can remain liquid even at temperatures well below freezing point.
Is there life salty lake Mars?
The exciting thing, however, is that if there is liquid water on the Red Planet, then maybe there could even be life there. Because terrestrial subglacial lakes and lye-filled sea ice channels prove that unicellular organisms occur even in such dark, salty water resources. “These waters at the base of the southern polar ice cap are therefore areas of great astrobiological interest,” say Pettinelli and her team.
Whether there actually is life on Mars is still pure speculation. An answer will probably only be found on site. "Future missions to Mars should target this region in order to examine this hydrological system, its chemistry and possible traces of extraterrestrial life more closely," the scientists state.