NASA spacecraft finds that water has been present on Mars for longer than previously thought

(ORDO NEWS) — Caltech researchers using the Mars Reconnaissance Orbiter have determined that surface water left behind salt minerals just 2 billion years ago.

Billions of years ago, rivers and ponds flowed on Mars, serving as a potential habitat for microbial life. Over time, the planet’s atmosphere thinned, water evaporated, leaving behind a frozen desert world that NASA’s Mars Reconnaissance Orbiter (MRO) is currently studying.

It is generally accepted that the water on Mars evaporated about 3 billion years ago. But two scientists studying data accumulated by MRO over the past 15 years have found evidence that significantly shortens this timeframe: Their study shows that signs of liquid water on the Red Planet appeared as early as 2-2.5 billion years ago, which means that water flowed there for about a billion years longer than previously thought.

The findings, published in the journal AGU Advances on December 27, 2021, relate to chloride salt deposits left behind by the evaporation of icy meltwater flowing across the landscape.

Although the shape of some of the valleys hinted that water may have flowed on Mars as recently as recently, the salt deposits represent the first mineral evidence to support the presence of liquid water. The discovery raises new questions about how long, if ever, microbial life could have persisted on Mars. On Earth, at least where there is water, there is life.

The study’s lead author, Ellen Lisk, did most of the research as part of her doctoral work at Caltech in Pasadena. She and Caltech professor Bethany Elmann used data from an MRO instrument called the Compact Reconnaissance Imaging Spectrometer of Mars (CRISM) to map chloride salts in the clay-rich highlands of Mars’ southern hemisphere, an area riddled with impact craters.

These craters were the key to the dating of the salts: The fewer craters an area has, the younger it is. By counting the number of craters on a particular area of ​​the surface, scientists can estimate its age.

There are two cameras on the MRO that are perfect for this purpose. A context camera with a black-and-white wide-angle lens helps scientists map chlorides. To zoom in, scientists turn to the High-Resolution Imaging Science Experiment (HiRISE) color camera, which allows them to see small details like a rover from space.

Using both cameras to create digital elevation maps, Lisk and Elmann found that many of the salt marshes are in depressions—there were once shallow pools—on gently sloping volcanic plains.

The scientists also discovered winding dry channels nearby – former streams that once fed surface runoff (from periodic ice melt or permafrost) into these ponds. Crater counts and evidence of salts at the top of the volcanic landform allowed them to date these deposits.

“It’s amazing that after more than a decade of providing high-resolution imaging, stereo and infrared data, MRO has allowed new discoveries to be made about the nature and timing of the formation of these ancient salt ponds associated with rivers,” said Elmann, Deputy Principal Investigator of CRISM. Her co-author, Lisk, is currently a postdoctoral researcher at Johns Hopkins University’s Applied Physics Laboratory, which leads the CRISM work.

Salt minerals were first discovered 14 years ago by NASA’s Mars Odyssey orbiter, launched in 2001. Equipped with higher resolution instruments than the Odyssey, MRO was launched in 2005 and has been studying salts and many other features of Mars ever since. Both vehicles are operated by NASA’s Jet Propulsion Laboratory in Southern California.

“Part of the value of MRO is that our understanding of the planet gets more and more detailed over time,” says Leslie Tampari, associate project supervisor at JPL. “The more of the planet we get with our instruments, the better we can understand its history.”

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