Scientists have recently discovered a 20-kilometer-wide subsurface lake of water on Mars.
The lake was discovered below the southern polar ice cap and is the first known stable body of liquid water on the planet. The Mars Express orbiter collected data from 2012 until 2015 using an on-board MARSIS radar. The lake resides in a rather flat area of the planet, save a depression on its eastern side.
It is rather peculiar for liquid water to exist near the polar cap of a planet that regularly experiences temperatures far below zero. However, scientists postulate that the water is able to stay liquid because of the presence of magnesium and calcium perchlorates, which have an antifreeze effect on the water. Roughly 1.5 kilometers of ice cover the lake, and the ice itself is a mixture of water and dust. On top of that, the regular ice is covered seasonally by a 1-meter layer of carbon dioxide ice.
The amount of data collected by the Mars Express is still greatly limited, and thus it is widely suspected that subsurface water can be found in locations throughout the planet.
The discoverers are still unsure of the quality of the water; it may be clear or it may be sludge-like. Regardless, the water has very high levels of salt, making it unsuitable for consumption by most life on Earth. Halophiles, organisms that thrive in salty conditions, would likely be unable to survive given the presence of magnesium and calcium perchlorate.
Until now, all water on Mars has existed as ice, water vapor, or liquid brines in the soil. Because of unsuitably low atmospheric pressure, the surface of the planet cannot sustain large bodies of liquid water, as it would immediately freeze or evaporate.
Scientists hope that this new discovery will help us to further understand Mars’ history as well as provide us with information regarding the potential for life on Mars.