Washington: It is generally believed that the water on Mars evaporated around 3 billion years ago.
But two scientists studying data from NASA’s Mars Reconnaissance Orbiter found signs of liquid water on the Red Planet just 2 to 2.5 billion years ago, meaning water was flowing there about a billion years older than previous estimates.
The findings, published in the journal AGU Advances, focus on salt chloride deposits left by the evaporation of icy meltwater flowing through the landscape.
While the shape of some valley networks hinted that water may have flowed on Mars recently, salt deposits provide the first mineral evidence confirming the presence of liquid water.
Liquid water has been flowing on the surface of Mars longer and more recently – by about a billion years – than previous estimates, according to new research using data from NASA’s Mars Reconnaissance Orbiter. Details: https://t.co/exLwUG14Kw pic.twitter.com/CBVwNQMhWr
– NASA Mars (@NASAMars) January 26, 2022
This discovery raises new questions about the microbial lifespan that could have survived on Mars, if it had ever formed. On Earth, at least, where there is water, there is life.
Ellen Leask, a postdoctoral researcher at the Johns Hopkins University Applied Physics Laboratory, along with Professor Bethany Ehlmann of the California Institute of Technology (Caltech), used data from the MRO instrument called the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM ) to map chloride salts across the clay-rich uplands of Mars’ southern hemisphere – terrain marked by impact craters.
These craters were one of the keys to dating salts: the fewer craters a terrain has, the younger it is. By counting the number of craters on an area of the surface, scientists can estimate its age.
MRO has two cameras which are perfect for this purpose. The pop-up camera, with its black-and-white wide-angle lens, helps scientists map the extent of chlorides.
To zoom in, scientists turn to the HiRISE (High-Resolution Imaging Science Experiment) color camera, allowing them to see details as small as a Mars rover from space.
Using the two cameras to create digital elevation maps, Leask and Ehlmann discovered that many salts were found in depressions – which once housed shallow ponds – on gently sloping volcanic plains.
Scientists have also found winding, dry channels nearby – ancient streams that once fed surface runoff (from occasional melting ice or permafrost) into these ponds. The counting of craters and the presence of salts at the top of volcanic terrain allowed them to date the deposits.
“What is amazing is that after more than a decade of providing high resolution imagery, stereo and infrared data, MRO has led to new discoveries about the nature and chronology of these ancient salt ponds connected to the river,” said Ehlmann of CRISM. Deputy Principal Investigator.
Salt minerals were first discovered 14 years ago by NASA’s Mars Odyssey orbiter, launched in 2001.
MRO, which has higher-resolution instruments than Odyssey, was launched in 2005 and has been studying salts, among many other features of Mars, ever since.