In 2018, a group of Italian researchers announced evidence to suggest the presence of subsurface lakes at Mars’ southern pole using data from MARSIS (The Mars Advanced Radar for Subsurface and Ionosphere Sounding). Aleyna Adamson looks at some new data which sheds light on the nature of these lakes.
MARSIS surveys the Martian surface by bouncing radio waves across the surface and measuring the intensity of the reflected echoes. In 2018, MARSIS surveyed an area of 200 km where unusually bright reflections were detected across a 20 km wide zone surrounded by regions of duller reflections. This suggested the presence of underground liquid.
On the 28th of September 2020, a team of scientists published an article in Nature Astronomy detailing their findings from a new set of MARSIS data. The new data was collected by extending the radar coverage over the initial 200km area and using a new method of analysis similar to the signal processing procedures applied to polar ice sheets on Earth.
It is most likely that the subsurface lakes have a very high salt content
This new method of analysis not only strengthened the claim of a subsurface lake beneath Mars’ south pole, but also indicated the presence of other smaller lakes nearby.
Due to the Martian atmosphere consisting primarily of carbon dioxide and being 1% of the thickness of Earth’s atmosphere, the surface is very cold. With the temperature averaging approximately -60 °C, it is impossible for these lakes to be pure water. It is most likely that the subsurface lakes have a very high salt content to prevent them from freezing in such low temperatures.
Don Juan Pond, a lake in the Antarctic, is the saltiest body of water on Earth. This lake is so salty that it would need temperatures of -53 °C for it to freeze. Considering the average temperature on mars, the liquids present in its newly discovered lakes would have to be even saltier than Don Juan Pond.
Many scientists still believe that the temperature of Mars is far too cold to freeze even the saltiest of liquids
Due to the high salinity of Don Juan Pond, many areas are virtually sterile but some have a sparse bacterial and yeast population with the occasional fungi. Applying this knowledge to the lakes on Mars it is very unlikely that the super salty waters would be able to sustain much life at all.
Even with the new MARSIS data, there is still a debate amongst the scientific community questioning whether the interpretation of this data is correct. Many scientists still believe that the temperature of Mars is far too cold to freeze even the saltiest of liquids. Others believe that the underground lakes may be evidence that Mars had an atmosphere similar to Earth and water once flowed on the Martian surface.
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