Mars’ water saga continues. New data from NASA’s Mars Reconnaissance Orbiter (MRO) spacecraft suggests that Mars water flowed at least a billion years longer than previously thought; or until some 2.5 billion to 2 billion years ago.
Many Mars researchers think that the red planet’s water evaporated some 3 billion years ago. But high-resolution imaging of chloride salt deposits by MRO’S Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) mapped chloride salts across the clay-rich highlands of Mars’ southern hemisphere – a terrain pockmarked by impact craters. Thus, this CRISM data indicates that water may have flowed much longer on the red planet than previously thought.
The findings – published recently in the journal AGU Advances focus on chloride salt-rich sediments that were left behind as icy mars surface meltwater began to evaporate. “Chloride salt deposits on Mars are intriguing because they dissolve very readily and thus record the last stage of liquid water present at Mars' surface,” the authors write.
These salt deposits, says NASA, provide the first mineral evidence confirming the presence of liquid water. And this discovery raises new questions about how long microbial life could have survived on Mars, if it ever formed at all, NASA notes.
The researchers found that many of the salts were in depressions – once home to shallow ponds – on gently sloping volcanic plains, says NASA. The scientists also found winding, dry channels nearby – former streams that once fed surface runoff (from the occasional melting of ice or permafrost) into these ponds, the agency reports.
“We find that chloride deposits are commonly draped atop underlying topography, often associated with channels, sometimes perched above deep craters in local topographic lows, and span a wide range of elevations,” the authors write.
NASA's Mars Reconnaissance Orbiter used its Context Camera to capture this image of Bosporos Planum, ... [+]
NASA/JPL-Caltech/MSSS
What’s most surprising and or significant about this new data?
These salts were formed by evaporation from flowing water sourced from the surface, e.g., snow or ice, rather than groundwater, Bethany Ehlmann, a planetary scientist at Caltech and the paper’s co-author, told me. Some of the deposits are younger than expected, meaning water was flowing on Mars and creating surface habitats late into its history, she says.
Where on Mars did water flow most recently?
“We aren't yet sure,” said Ehlmann.
On a large scale it is either in these chloride deposits; a few silica deposits near Valles Marineris, or along small valley networks, says Ehlmann. However, she leaves the door open that on much smaller scales surface water could have flowed much more recently, and may even persist somewhere on Mars to the present day.
NASA’s mantra for Mars exploration has long been follow the water. To date, there’s no incontrovertible evidence for water flowing atop the Martian surface at present. But this latest MRO data only emphasizes how important it is to stay the course in current and future Mars exploration.
With the increasing detail of each new data set, researchers are able to push Mars’ water timeline further and further up. No matter how barren mars may be today, clearly, it has hydrologic secrets to share.
“Part of the value of MRO is that our view of the planet keeps getting more detailed over time,” Leslie Tamppari, the MRO deputy project scientist at JPL said in a statement. “The more of the planet we map with our instruments, the better we can understand its history.”
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