There is mounting evidence that Mars, now cold and dry, had liquid water running across its surface much more recently than previously thought.
Scientists have long believed that Mars it was wet about 3 billion years ago, during the planet’s hesperian period, and then lost much of its water. But a new study presents evidence of water activity from just 700 million years ago, well into the current Amazonian period, posing a new puzzle to unravel about the Red Planet and its history.
The new study is based on data from China’s Zhurong rover, which is part of the tianwen-1 and touched down on the surface of Mars in May 2021. Notably, scientists used data the rover collected during its first 92 Martian days, or sols, at its landing site on Utopia Planitia. Yang Liu, a researcher at the National Space Science Center (NSSC) of the Chinese Academy of Sciences (CAS), and colleagues analyzed data from three different instruments at Zhurong: the Laser-Induced Decay Spectrometer (MarSCoDe), the Telescopic Camera microimaging and shortwave infrared spectrometer.
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Those instruments studied minerals that the team say suggest the presence of a substantial amount of liquid water at the site about 700 million years ago, well into the current Amazonian epoch, which scientists previously thought was dry.
“This is a very interesting result,” says Eva Scheller, a planetary scientist at the California Institute of Technology who was not involved in the new research. “We have very little recorded evidence of ‘young’ liquid water systems on Mars. And the ones we do have were generally in the form of salt minerals.”
But the Zhurong instruments detected water molecules locked in the rock, “which is very interesting and different from other young liquid water environments that have been observed,” Scheller said. “It means that particular forms of water-bearing minerals would have formed at much later time periods than previously considered in other scientific studies.”
NASA has sent its Mars rovers to ancient landing sites, dating back to the age of Noah more than 3.7 billion years ago. Zhurong, then, is not just another set of wheels on Mars, but a powerful set of instruments exploring a new, geologically young site to open new windows of opportunity for Mars research.
“One of the biggest things we’re going to have to discover that I hope to see from the Zhurong rover is just how extensive these ‘young’ water-bearing minerals are,” Scheller said. “Are they common or uncommon in these ‘young’ rocks?”
Zhurong has now traveled about 1.24 miles (2 kilometers) during his more than 350 Martian days, and has analyzed a variety of features in his travels, meaning there is likely still more new Martian insights to be gained from the rover.
The results are described in a paper published Wednesday (May 11) in the journal Science Advances.
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