Cracks, crusts and ridges in Martian sand dunes point to the presence of water near the planet’s equator as recently as 400,000 years ago, according to an analysis of data from China’s Zhurong rover, published in the journal Science Advances.
While the rover did not gather any direct evidence of water, the findings suggest that liquid water may have flowed in this region of the Red Planet much closer to the present than previously thought.
“We’ve seen these features before,” Aditya Khuller, a planetary scientist at NASA’s Jet Propulsion Laboratory who did not participate in the research, tells Science News’ Allison Gasparini. “But they’re usually much older.”
Water in some forms does exist in and around Mars today. The planet’s atmosphere contains small amounts of water vapor, for example. Mars also has water ice caps at its poles, and salty water may sometimes flow down hillsides and crater walls, according to NASA. During the Martian winter, water frost may form, and water-based snowflakes drift through the atmosphere, turning to gas before they hit the ground.
Scientists also think that bodies of water once existed on Mars’ surface, but they evaporated billions of years ago.
Currently, China’s Zhurong rover is not communicating with Earth, as dust has likely coated its solar panels, starving it of energy. But for the study, scientists examined data the rover had already collected in Utopia Planitia, a basin north of Mars’ equator where it landed in May 2021. For nine months, the rover studied the structure and chemical makeup of four sand dunes around its landing site.
The rover found depressions, ridges and cracks on the surface that could not be explained by wind, which would have eroded the crust instead of creating these features. And frost made from carbon dioxide could not be the cause, since it wouldn’t have formed that close to the equator.
Instead, the team hypothesizes that water vapor condensed as frost and snow on the surface of the dunes, then melted when it mixed with sand. High temperatures during Martian mornings would have evaporated that salty water, leaving salt and minerals that combined with the planet’s sand to create a hard crust, writes Space.com’s Sharmila Kuthunur. With more heat, this crust eventually cracked.
The paper estimates that the dunes’ geological features formed 1.4 million to 400,000 years ago, suggesting that Mars’ climate at that time could have been more humid than previously thought, the authors write.
The dunes’ geological features indirectly show that liquid water could have existed when they formed, Manasvi Lingam, an astrobiologist at the Florida Institute of Technology who did not contribute to the research, tells USA Today’s Terry Collins.
“The phenomenon was documented at one site, but it should be applicable to a fairly large fraction of Mars’ surface at similar latitudes,” Lingam tells Space.com.
The study provides “evidence that there may be a wider distribution of this process on Mars than previously identified,” Mary Bourke, who studies Mars’ geology at Trinity College Dublin and did not participate in the study, tells Marcia Dunn of the Associated Press.
Since Mars’ atmospheric conditions today are similar to those of 400,000 years ago, the findings suggest liquid salt water may currently exist near the equator, Xiaoguang Qin, a co-author of the study and a geologist at the Chinese Academy of Sciences, tells Science News. As space agencies on Earth turn their attention to the Red Planet, such water sources would be crucial for future Mars-bound astronauts.