A lake has been found beneath Mars’ south polar ice cap in the Planum Australe region, approximately 20 kilometres in diameter. This is the first time that liquid water has been observed in a stable state on the red planet. Previously dried up lake beds have been found on the surface as well as the much-debated observation of small amounts of liquid water dripping down Martian slopes in 2010.
The discovery was made by the MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) team lead by Roberto Orosei , using a radar on board the Mars Express orbiter in order to fire rays down into the surface to probe beneath. As the waves bounce off different materials within the ice the brightness of the reflections can be used to map what materials lie underneath. Whilst the radar was unable to accurately measure the depth of the lake, scientists estimate it to be at least one meter.
As the waves bounce off different materials within the ice the brightness of the reflections can be used to map what materials lie underneath
These results are the accumulation of three years of observation from the European Space Agency’s orbiting express spacecraft, in total 29 separate radar scans were used to make the discovery. This method of using radar to find liquid lakes of water under polar ice caps has been used before on Earth. Underground lakes in Greenland and Antarctica have been found this way.
At first, the team thought it might have been a layer of CO2 but it was ultimately decided that this was not possible as a different radar signal would have been produced. This left the team with only one possibility: they had found a lake of liquid water.
This method of using radar to find liquid lakes of water under polar ice caps has been used before on Earth
Whilst this is exciting (and long awaited) news, this study does not suggest anything about life on Mars. It may, however, help scientists narrow down a location to look for past life. The composition of the water found is also not especially hospitable, as in order to remain in a liquid state at the cold temperatures found at Martian poles there would be a very high salt concentration. If this is the case the lake would be more of a brine than liquid water, conditions that would make it nearly impossible for life to exist as we understand it.
This paper has been widely accepted within the scientific community, although like all great scientific discoveries, the next step must be further research and collaboration. Readings from NASA’s Mars Reconnaissance Orbiter (MRO) has seen no sign of the lake yet, despite using three-dimensional views of the poles. It could be possible that the readings observed by the MRO radar are scattered in a different way, or that these wavelengths do not penetrate deep enough into the ice to record the lake. A future collaboration between the MARSIS and MRO teams is likely in order to further confirm this discovery.
It could be possible that the readings observed by the MRO radar are scattered in a different way, or that these wavelengths do not penetrate deep enough into the ice to record the lake
These last few months have been very exciting for our closest planetary neighbour, with the discovery of organic molecules announced a few weeks ago and now the discovery of a large body of liquid water. What secrets will the red planet reveal next?