The signs of wave ripples in the sandy shores of ancient lake beds, created as wind pushed water back and forth have been found on Mars providing evidence that there were open bodies of water, not just ice, on the planet's surface.
"The shape of the ripples could only have been formed under water that was open to the atmosphere and acted upon by wind," said Claire Mondro, postdoctoral scholar at the California Institute of Technology, and the first author of a study published in Science Advances in a statement.
The finding of ripples in Martian rocks is an indicator of the presence of an ancient body of water on the planet's surface. The researchers estimate that the ripples were formed 3.7 billion years ago when Mars was warm enough to support liquid water open to the air.
The ripples are small, about 6 millimeters high and 4 to 5 centimeters apart. Computer modeling, created from the data of the ripples was used by scientists at Caltech to estimate that they were formed in a shallow lake, less than about 2 meters deep.
When Mars Became Drier
When the ripples were formed, scientists believe that Mars was becoming drier, and the longer the conditions were warm enough for water, the longer the opportunity that existed for life to develop.
"Extending the length of time that liquid water was present extends the possibilities for microbial habitability later into Mars history," Mondro said.
The presence of water indicates that Mars once had a far denser atmosphere than today, one that was capable of sustaining warmer temperatures.
Over time, the planet's climate changed dramatically, leading to loss of surface water and thinning of its atmosphere.
How Long Did Martian Lakes Exist?
The further study of the ripple formations could help scientists to pinpoint how long these ancient lakes existed on Mars, giving early life the opportunity to grow.
The NASA Curiosity rover discovered one set of ripples in a region that once contained windblown dunes, while the other set was found in a location and manner that suggested to scientists that they had been formed in an ancient lake.
"The discovery of wave ripples is an important advance for Mars paleoclimate science," John Grotzinger, Harold Brown Professor of Geology at Caltech and the former project science for Curiosity's mission,the Mars Science Laboratory said in a statement.
"We have been searching for these features since the Opportunity and Spirit landers began their missions in 2004," said Grotzinger.
"Earlier missions, beginning with Opportunity in 2004, discovered ripples formed by water flowing across the surface of ancient Mars, but it was uncertain if that water ever pooled to form lakes or shallow seas.
"The Curiosity rover discovered evidence for long-lived ancient lakes in 2014, and now 10 years later Curiosity has discovered ancient lakes that were free of ice, offering an important insight into the planet's early climate."
Reference
Mondro, C. A., Fedo, C. M., Grotzinger, J. P., Lamb, M. P., Gupta, S., Dietrich, W. E., Banham, S., Weitz, C. M., Gasda, P., Edgar, L. A., Rubin, D., Bryk, A. B., Kite, E. S., Caravaca, G., Schieber, J., & Vasavada, A. R. (2025). Wave ripples formed in ancient, ice-free lakes in Gale crater, Mars. Science Advances, 11(3). https://doi.org/10.1126/sciadv.adr0010
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