Thanks to its carved topography, researchers have always suspected that Mars was once home to several rivers, lakes, and perhaps even oceans. There has even been some speculation about the existence of frozen water deep beneath the ground. However, finding evidence of liquid water in the present day, has been a little elusive. That is why NASA's September 28th announcement that confirmed the detection of liquid brine on the Red Planet caused so much excitement.
The first indication of the fluid's presence came in 2011 from high-resolution images captured by the Mars Reconnaissance Orbiter (MRO), which has been orbiting the Red Planet since 2006. They showed dark streaks that appeared to be flowing down the inner walls of the Newton crater in the Red Planet's Southern Hemisphere. What made the water theory plausible was that the "flows" were only visible during the 'warmer' spring through the autumn period.
While cautiously optimistic, the scientists needed concrete evidence to confirm the streaks that they dubbed 'recurring slope lineae', or 'RSL' were a result of flowing water.
For that Lujendra Ojha of Atlanta's Georgia Institute of Technology and his team turned to MRO's visible and Infrared spectrometers.
The instruments can read the hundreds of 'colors' in the sunlight reflected off of the Red Planet's surface and discern patterns. The images produced allows scientists to identify minerals on the planet's surface.
According to the researchers, the spectrometer images showed the presence of hydrated salts at some RSL locations when the dark streaks were relatively broad. In areas where they are not as spread out, there was no sign of the minerals. The selective presence of the salts, a mixture of chlorates and perchlorates, led the scientists to confirm their earlier suspicion that the streaks are indeed caused by liquid water.
Also, as initial observations suggested, the water flow exists only during the planet's summer months when the temperatures 'warm' up to above -10° F (-23°Ç). The researchers say the water can remain in liquid form in such frigid conditions because of the presence of salt that helps lower its freezing point way below the average 32°F (0°Ç). However, even the salt cannot stop it from turning to ice during autumn and winter when the surface temperatures drop as low as -195°F (-125°Ç).
As of now, scientists are not sure where the water is sourced from. They hypothesize that it may be seeping up from underground ice or aquifers, or condensing out of the thin Martian atmosphere. Though the mystery could easily be solved with a water sample, it is not possible even though NASA's Mars Curiosity Rover is just about 30 miles away from the source.
That's because the Outer Space Treaty of 1967 prevents any nation from getting too close to a water source on another planet, for fear that it might contaminate it with microbes from Earth.
The one hope scientists have of getting near the liquid is with the help of the organic molecule analyzer that the European Space Agency plans to send on its 2018 ExoMars mission. While its primary purpose is to look for evidence of life on the Red Planet, it may be able to get near enough to the water flow and collect samples if complete sterilization can be guaranteed. Meanwhile, researchers have marked the areas where the water seems to be coming from as targets for future potential human mission sites.
Finding water on Mars has left researchers thirsting for more. They are now competing for funds to send rovers to investigate if there is liquid water on Jupiter's icy moon, Europa. There are currently two separate missions in the works to land on the distant satellite by 2020.
Whether there is alien life on Mars remains to be seen. But the presence of the liquid brine has undoubtedly increased the possibility. As Jim Green, NASA's director of planetary science said: "If you look at Earth, water is an essential ingredient. Wherever we find water, we find life." Watch out Martians, the Earthlings are coming!