Signatures of Ice-Free Ancient Ponds and Lakes Found on Mars
In a groundbreaking discovery, scientists using data from NASA's Curiosity
rover have identified two distinct sets of wave ripples preserved in Martian
rock formations. These features, formed roughly 3.7 billion years ago, point
to the presence of shallow, ice-free lakes that were open to the Martian
atmosphere, challenging previous climate models that suggested Mars's
surface was largely covered in ice during that period.
Wave ripples—small, undulating patterns formed in sandy lakebeds by the gentle lapping of water—are among the clearest geological indicators of ancient standing water. Their presence on Mars provides direct evidence that liquid water once flowed freely under atmospheric conditions conducive to habitability.
Ancient Martian Climate Reimagined
The study, published in Science Advances, suggests that Mars's climate and atmosphere were warm and dense enough to sustain liquid water on the planet’s surface for a longer period than previously thought. The findings extend the timeline during which microbial life might have been possible on Mars.
“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, a postdoctoral scholar and the study’s lead author.
The ripples are small—approximately 6 millimeters in height and spaced 4 to 5 centimeters apart. Using computer models, co-author Michael Lamb, an expert in sedimentology, deduced that the waves creating these ripples likely occurred in a lake less than 2 meters deep.
“This discovery reshapes our understanding of the Martian climate during the planet’s transition to drier conditions,” Mondro added.
Evidence from Gale Crater
The wave ripples were uncovered in 2022 as the Curiosity rover explored the Gale Crater, a site that has revealed a rich geological history of Mars’s aqueous past.
- The Prow Outcrop: This site contains one set of ripples formed within wind-blown dunes, marking an earlier period when liquid water interacted with the Martian surface.
- Amapari Marker Band: Located nearby, this site hosts ripples suggesting the presence of a shallow lake, possibly holding up to 2 meters of water.
Together, these sites demonstrate that the atmospheric conditions required for liquid water occurred at multiple points in Martian history, offering new insights into the planet’s ancient environment.
Decades in the Making
John Grotzinger, Harold Brown Professor of Geology at Caltech and a co-principal investigator on the study, called this discovery a culmination of years of exploration and research:
“We have been searching for these features since the Opportunity and Spirit missions began in 2004. Earlier missions revealed evidence of water flowing across the Martian surface, but it remained uncertain whether it pooled into lakes or shallow seas. Now, Curiosity has uncovered evidence of lakes that were ice-free, providing a critical piece of the puzzle about Mars’s early climate.”
The discovery builds on Curiosity’s earlier findings in 2014, which confirmed the presence of long-lived ancient lakes. These new findings, a decade later, demonstrate that some of these lakes were exposed to the atmosphere, further advancing our understanding of Mars’s climatic and geological history.
Broader Implications
By extending the timeline for liquid water on Mars, the discovery increases the likelihood that the planet could have supported microbial life later in its history than previously assumed.
“This opens up a new chapter in our understanding of Mars as a potentially habitable world,” Grotzinger said.
Collaboration and Support
The study, titled Wave ripples formed in ancient, ice-free lakes in Gale Crater, Mars, was conducted by an international team of scientists from institutions including Caltech, the University of Tennessee, Imperial College London, and UC Berkeley.
The research was supported by funding from NASA, the UK Space Agency, and the French Space Agency.
