Scientists examining data from China’s Zhurong rover have found cracked layers on tiny Martian dunes for the first time, suggesting the Red Planet was a saline water world as recently as 400,000 years ago.
Since landing In the northern hemisphere of Mars, the rover rolled near four nearby crescents in May 2021 sand dunes in the Utopia Planitia region to study their surface composition. All four tiny, wind-sculpted geological features are covered with thin, ubiquitously fractured crusts and ridges formed by the melting of small pockets of “modern water” sometime between 1.4 million and 400,000 years ago, according to a new paper (opens in new tab) published on Friday (April 28).
“This marks a more recent time in the history of Mars,” Xiaoguang Qin, a scientist at the Chinese Academy of Sciences in Beijing and author of the new study, told Space.com.
Related: Water on Mars: Exploration & Evidence
Scientists have long thought so early Mars was home to plenty of liquid water about three billion years ago. But dramatic climate changes froze much of it as ice was now trapped in the poles, drying out most of the planet.
Located near where they landed in the planet’s northern hemisphere — far from the North Pole — the dunes Zhurong explored are just under 15 to 30 meters long and around 1 meter high. Latest findings from the analysis of images and data sent home by Zhurong and his family tienwen 1 Orbiter Companion show that a few million years ago, significant amounts of water from the planet’s frigid polar regions flowed to lower latitudes and settled on the dunes of Utopia Planitia.
As Zhurong ventured close to his target dunes, which are tiny compared to NASA’s massive two-story Curiosity rovers educated Elsewhere on Mars, the rover’s onboard laser-induced decay spectrometer (MarSCoDe) broke up sand grains into millimeter-sized particles. Their chemical composition showed hydrated minerals such as sulfates, silica, iron oxide and chlorides. According to the study team, these minerals formed in the presence of water at low latitudes in the late Amazon era on what scientists previously thought was bone-dry Mars.
Researchers say water vapor migrated from the poles of Mars to lower latitudes like Zhurong’s Spot several million years ago, when the planet’s polar ice caps released large amounts of water vapor thanks to a different tilt that Mars’ poles had aimed more directly at the sun. Freezing temperatures on the wobbling planet condensed the drifting steam and caused it to fall as snow far from the poles, according to the latest study.
Mars’ tilt changes over a 124,000-year cycle, so “this provides a replenishment mechanism for vapor in the atmosphere to form frost or snow at low latitudes where the Zhurong rover landed,” Qin told Space .com But “no water ice was detected by any instrument on the Zhurong rover.”
Instead, salts in the sand dunes of Mars warmed the fallen snow in much the same way salting roads on Earth during storms melts icy patches and thaws them enough to form salt water. The process also formed minerals like silica and iron oxides that Zhurong discovered, researchers say.
However, the salt water did not last long. temperatures on Mars rocking and spiking wildly between 5 and 6 a.m. in the morning, allowing the saltwater to evaporate, leaving behind salt and other newly formed minerals, which later seeped between the dune’s sand grains and cemented them into a crust, the study found.
The crust that formed on top of the dunes, which is only 1.25 to 1.7 cm deep, likely formed in just a year because the loose dunes would not stay in place long enough to solidify millennia. It then ruptured when high temperatures dehydrated it so much that it “should be tough and resist wind erosion,” Qin said.
“The phenomenon has been documented in one location, but it should be applicable to a fairly large portion of the Martian surface at similar latitudes,” says Manasvi Lingam, an assistant professor of astrobiology at the Florida Institute of Technology who was not involved in the new research, Space said .com
Since Zhurong now choked under dust coated solar panelsUncovering water activity on and in saline Martian dunes, researchers in the new study suggest future missions to look for salt-tolerant microbes, perhaps like Artemia or Pickleweed, that live in the Great Salt Lake in Utah, United States.
This research is described in a Paper (opens in new tab) published Friday (April 28) in the journal Science Advances.
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