NASA has found the currently strongest evidence of water on the surface of Mars. The scientists have not exactly seen flowing water but only some dark streaks of soil that flow down steep slopes in the warmest months on Mars. These streaks are made up of liquid hydrated perchlorate salts.
First spotted in 2011 by Lujendra Ojha at the Georgia Institute of Technology and colleagues at labs connected with NASA, these streaks of salts are called recurring slope lineae (RSL). As the name indicates, these lines appear on slopes in roughly the same place every year. The RSL are about 5 meters wide and range about 200 to 300 meters in length. Though fading in the winter, when they reappear they stretch across long distances. These RSL are found at many places along the Martian equator.
RSL were first identified in the images taken by the Mars Reconnaissance Orbiter. Though the camera used had a high resolution, the scientific instrument (spectrometer) had low resolution. So, after three years of observations, data collection and analyses, the scientists have shown that the hydrated salts are present inside the RSL. This brings us to their strongest hypotheses put forth to explain the flow pattern, i.e. evidence for flowing water on the surface of Mars.
Perchlorates are corrosive, toxic compounds that are abundant on Mars. Calcium Perchlorate, one of the compounds found on Mars, is extremely hygroscopic, i.e. it can attract and hold water from its surroundings. The resulting salt solution or ‘brine’ is stable and alters water’s physical properties. It effectively lowers water’s freezing point and the pressure at which it evaporates. This makes the brine exist for fairly long periods of time on the surface of Mars.
However, we must not get ahead of ourselves. The scientists believe that the water is more of a “seep” than a flow. They think there is a very small quantity of water on the Martian surface.