Caltech researchers John Grotzinger and Michael Lamb announced findings about Mars' climatic history in a paper published in the journal Science Advances. The study revealed evidence of ancient liquid water on Mars, indicated by wave ripples preserved in the Martian rock record.
In 2022, NASA's Curiosity Rover discovered two sets of wave ripples at the bottom of Gale Crater, suggesting the previous presence of shallow water that was open to the Martian atmosphere, not covered by ice as some climate models would require, according to Phys.org. These ripples are small undulations on sandy shores of lake beds, created when wind-driven water moves back and forth.
According to Universe Today, one set of ripples, known as the Prow outcrop, was discovered in a region that once contained wind-blown dunes. The other set was found nearby in the sulcate-rich Amapari Marker Band of rocks, indicating the presence of a lake with up to two meters of water, somewhat later in Mars' history than the Prow.
"The shape of the ripples unequivocally indicates the presence of water in lakes that was subjected to wind influence," stated Claire Mondrón, the lead author of the study from the California Institute of Technology.
The ripple height of about six millimeters and spacing of four to five centimeters tell us that the lake was shallow, possibly even less than two meters deep. These small ripples in fine sand are formed by the action of small waves created as wind-driven water laps back and forth.
According to Futura Sciences, geologists quickly identified the wave ripples discovered by Curiosity because they are similar to structures found on Earth in coastal environments. "Ripples are one of the clearest indicators of an ancient standing body of water that can be provided by the geological record," the researchers noted.
"Since the first missions Opportunity and Spirit in 2004, we have been searching for evidence of ancient lakes on Mars, and they have finally been found," said Grotzinger, the Harold Brown Professor of Geology at Caltech and one of the leaders of the study.
As noted by Semana, a question remains: until when did Mars manage to preserve liquid water on its surface, especially considering the evidence of ripple formation around 3.7 billion years ago, a period when Mars was thought to be becoming drier. Researchers estimated that these wave ripples date back to that time, suggesting that habitable conditions may have lasted longer than previously thought.
"Extending the time period in which liquid water was present expands the possibilities of microbial habitability later into Mars' history," Mondrón said, according to Semana.
Mars underwent a major climatic transition that definitively changed its landscape, and it is still difficult to know when and how this transition occurred—whether it was abrupt or gradual. The new data confirms that in the past, Mars had conditions favorable for the existence of liquid water, expanding the prospects for studying its habitability.
In 2014, Curiosity Rover discovered evidence of ancient long-lasting lakes, and its recent findings continue to provide insights into the early conditions on Mars, with perhaps bodies of liquid water dotted across the landscape.
Michael Lamb, a Professor of Geology at Caltech and an expert on the interactions between sediment, water, and atmosphere on Earth, created computer models from the ripples to determine the size of the lake that created them. This size constraint limits the original setting to a shallow lake of less than about two meters deep.
The article was written with the assistance of a news analysis system.