Salt water may have flowed near the equator of Mars as early as 400,000 years ago


Crusts, cracks and other geological features on sand dunes near the Martian equator lead researchers to believe that water may have been there much later than previously thought.

The features, likely caused by the movement of molten salt water, were discovered in images taken by China’s Zhurong rover. Chemical analysis of the rover suggests they could have formed as recently as 400,000 years ago, researchers report April 28 in Science Advances .

The results could help future missions to find life on Mars. Atmospheric conditions on Mars 400,000 years ago were similar to those observed today, suggesting that liquid salt water still exists at the planet’s low latitudes, said Xiaoguang Qin, a geologist at the Chinese Academy of Sciences in Beijing.

The Zhurong rover — China’s first rover — landed on the Red Planet in May 2021 in a region called Utopia Planitia, north of the Martian equator. For nine months, the rover collected images and information about the chemical composition of the region’s dunes and measured cracks found along the sand surfaces.

When Qin and his team first saw the image of the rover, they were surprised. It seemed that the features of the crust are related to the activity of water. The wind will not leave these geological traces; this would instead erode the bark. There will also be no frost dioxide; it would not be present at lower latitudes. The team concluded that melting pockets of frozen water best explained the features found on the dunes.

Mapping the number and size of meteorite craters in the area has provided a rough estimate of the age of the dunes, which are believed to have formed between 1.4 million and 400,000 years ago. This suggests that there was water in the region hundreds of thousands of years ago, not billions of years ago as previously thought.

It’s the combination of features seen in the dunes with age that makes the new study special, says Aditya Huller, a planetary scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California. “We’ve seen these features before,” Huller says. “But they’re usually much older.”

Previously, scientists also found evidence for the existence of modern water ice in the ravines of the middle latitudes of Mars. And data from NASA’s landers hint that liquid brines may exist on the planet in the mid-to-high northern latitudes, although it would be too cold for life.

Qin says data from the Zhurong rover indicates a relatively mild temperature on Earth, suggesting that Mars’ low-latitude sand dunes may be hospitable to life.

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