Dark, narrow streaks can be seen 'flowing' downhill on this portion of Horowitz Crater, leading scientists to conclude the existence of a seasonal flow of water on today’s Mars. The streaks seen in this image are roughly the size of a football field. Image credit: NASA/JPL-Caltech/Univ. of Arizona
The discovery has massive implications for the search for life on the Red Planet, NASA has said.
Speculation about the existence of water began with the discovery of streaks on Martians slopes in 2010, which were thought to be signs of hydrated minerals.
The streaks seem to change over time, darkening and appearing to flow downhill during warm seasons and then fading in colder seasons.
These streaks are found in several locations on Mars when temperatures rise past minus 23°C.
Known as recurring slope lineae (RSL), they had previously been seen as potentially a sign of the presence of liquid water, but new findings of hydrated salts on the slopes have strengthened this theory.
The hydrated salts would lower the freezing point of the liquid, just as salt is seen to melt ice and snow during winter on Earth.
NASA believes this points to a shallow subsurface flow of liquid water, with enough rising to the surface to explain the darkening.
“Our quest on Mars has been to 'follow the water,' in our search for life in the Universe, and now we have convincing science that validates what we've long suspected," says John Grunsfeld, associate administrator of NASA's Science Mission Directorate in Washington.
"This is a significant development, as it appears to confirm that water - albeit briny - is flowing today on the surface of Mars."
"We found the hydrated salts only when the seasonal features were widest, which suggests that either the dark streaks themselves or a process that forms them is the source of the hydration.
In either case, the detection of hydrated salts on these slopes means that water plays a vital role in the formation of these streaks," says Lujendra Ojha of the Georgia Institute of Technology, lead author of a report on these findings.
"When most people talk about water on Mars, they're usually talking about ancient water or frozen water," he continues.
"Now we know there's more to the story.
This is the first spectral detection that unambiguously supports our liquid water-formation hypotheses for RSL."