Researchers from the California Institute of Technology have uncovered two sets of ancient wave ripples on Mars, preserved in the planet’s rocky surface. These ripples, small undulations in sandy lakebeds formed by the movement of water, are a clear indication of long-gone bodies of liquid water on the Martian surface. Their discovery suggests that shallow lakes existed billions of years ago, open to the Martian atmosphere and not frozen over, as some climate models had previously predicted.
What are wave ripples?
Wave ripples are formed when wind-driven water moves back and forth, creating small, regular patterns in sandy surfaces. On Mars, these features are particularly significant as they provide evidence of standing water in the planet’s past. The recently discovered ripples are estimated to be about 3.7 billion years old, a time when Mars was thought to be transitioning into a drier and colder climate.
“The shape of the ripples could only have been formed under water that was open to the atmosphere and acted upon by wind,” explained Claire Mondro, postdoctoral scholar and lead author of the study.
Evidence of shallow Martian lakes
Michael Lamb, a geology professor and expert in sediment-water interactions, used computer models to analyze the ripples. The small size of the ripples—just 6 millimeters high and spaced 4 to 5 centimeters apart—indicates they were shaped by gentle waves in shallow water. These findings suggest the lakes were no more than 2 meters deep. The research team emphasizes that this discovery pushes the timeline of liquid water on Mars further than previously thought. “Extending the length of time that liquid water was present extends the possibilities for microbial habitability later into Mars’s history,” Mondro added.
Where were the ripples found?
The ripples were discovered by NASA’s Curiosity Rover n 2022 as it explored the Gale Crater. One set, found in the Prow outcrop, formed in an area that once hosted wind-blown dunes. The other set, discovered nearby in the Amapari Marker Band of rock, points to a shallow lake with up to 2 meters of water. These findings suggest that such atmospheric and climatic conditions occurred multiple times in Mars’s history. “The discovery of wave ripples is an important advance for Mars paleoclimate science,” said John Grotzinger, a key investigator and former project scientist for Curiosity.
The Curiosity rover has built on discoveries made by earlier Mars missions. While NASA’s Opportunity rover in 2004 found evidence of water flowing across the planet’s surface, it remained unclear whether liquid water had ever pooled into lakes or seas. In 2014, Curiosity found evidence of long-lasting lakes. “Curiosity has discovered ancient lakes that were free of ice, offering an important insight into the planet’s early climate,” Grotzinger explained.
Source: Caltech University of Technology.
Image credit: NASA/JPL-Caltech/MSSS.
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