Scientists have debated for the past thirty years whether liquid water exists on Mars. That debate has now been put to rest.  According to an article published in Science, a lake of liquid water has been detected on Mars; the first to be discovered on the planet. 
The body of water is deep below an ice cap on the south pole of the planet and was uncovered by an ice-penetrating radar. Scientists infer that the lake is uninhabitable due to the water’s high salt content and extremely low temperature. The dissolved salts and pressure from the ice above have kept the water unfrozen. 
Martin Siegert, a geophysicist at Imperial College London, claimed that the Mars lake looks similar to interconnected pools that lie below several kilometers of ice in Greenland and Antarctica. 
However, the Mars lake probably formed through a different process than those on Earth. Gullies and channels visible on the planet’s surface that were once presumably created by water flow are evidence that water was present on Mars billions of years ago, when the atmosphere was warmer and denser.
The present atmospheric pressure of Mars is now so low that any water lying on the surface would boil away. The only water to still exist on Mars remains in ice deposits below the surface and in frozen polar ice caps.
The liquid lake was identified by the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS), a technology that is part of the Mars Express orbiter, a space exploration program started by the European Space Agency in 2003. Early on in the mission, MARSIS scientists had disregarded signals of water near the south pole as they would only appear occasionally. 
Years later, the team realized that the computer on the orbiter had been trying to reduce the amount of data it had to process, which had accidentally caused any abnormal signal to be suppressed. Once the computer’s problem was fixed, the existence of the liquid lake on the south pole was confirmed. 
Although it is unlikely that life, as we know it, will ever be able to survive in this location, the discovery of the liquid lake has already prompted researchers to search for other lakes under the ice. 
Europe’s ExoMars rover contains a new radar being developed that is planned to launch in 2020 with the goal of finding water at a warmer location that could be more suitable for life.