NASA Has Strongest Evidence Yet That There's Flowing Water on Mars

Those flow marks we thought were salty liquid water are most likely salty liquid water, according to a new study.

Sep 28 2015, 3:00pm

Photo by NASA/JPL-Caltech

New research from NASA "strongly supports" the belief that there is liquid water flowing on Mars, either on the surface or just below it.

The new evidence comes from taking a closer look at recurring slope lineae (RSL): streaks of, well, something, that appear on the slopes of Mars craters in the warmer months and follow flow patterns, like what you'd expect of water. These streaks were first discovered in 2011 and researchers have long hypothesized that they could be caused by the flow of liquid water formed by salts soaking up the water vapor in the atmosphere (or melting the frozen surface water) and becoming liquid brine. But we didn't have any evidence that this was what was happening, until now.

This composite of images from 2011 shows how the RSL disappear and reappear throughout the year. Source: NASA

NASA researchers used the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) to measure the areas where the RSL appear and look for hydrated salts (salts that have absorbed water), according to a paper published today in Nature Geoscience. In every site they looked at, the RSL slopes also contained hydrated perchlorate salts (salts formed from perchlorate acid), "supporting a genetic connection between the two," the paper reads. In other words: yeah, it is really likely these dark streaks are formed by salty, liquid water on Mars.

These images show the RSL flowing from bedrock at Horowitz crater on Mars. Source: Nature Geoscience

We've known Mars has ice and snow for awhile now, and have found trace amounts of water vapor in the atmosphere, but the search for liquid water—which would be necessary to support life as we know it—has proven more elusive. Mars's weak atmosphere and low temperature means any liquid water should either instantly freeze or instantly evaporate (depending on where it is and the time of year and day) on the surface of the red planet. But salt lowers the freezing temperature of water (that's why we use it on our roads in the winter) meaning salty brines could potentially allow liquid water to flow, at least on some warmer summer days, even on the Red Planet's harsh surface.

This isn't exactly final proof of liquid water on Mars, but it adds to the growing evidence that the RSL are indeed salty streaks of water, which is a very exciting proposition. Liquid water would be a huge stride forward in the search for microbial life somewhere on Mars, though the paper notes even if these RSL are formed by liquid brine, "the water activity in perchlorate solutions may be too low to support known terrestrial life." But it doesn't say anything about unknown Martian life. The search continues.