Scientists have identified evidence that shallow lakes on ancient Mars once held liquid water exposed to the atmosphere.
This discovery challenges some climate models that propose all Martian water was covered by ice.
Planetary geologists and astronomers have long debated the form and duration of water on Mars since NASA’s Mariner 9 mission in the 1970s revealed dry gullies.
The new findings, published on January 15, reveal wave ripples—small ridge-like structures—photographed by Curiosity in two ancient lakebeds within Gale Crater.
“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 sedimentologist at CalTech and lead author of the study.
The ripples, measuring 0.2 inches (6 millimeters) in height and spaced 1.6 to 2 inches (4 to 5 centimeters) apart, suggest the lakes were less than 2 meters (6.5 feet) deep.
Both lakebeds are estimated to have formed around 3.7 billion years ago, indicating Mars had a denser, warmer atmosphere capable of sustaining liquid water for an extended period.
“Extending the length of time that liquid water was present extends the possibilities for microbial habitability later into Mars’s history,” Mondro added.
This raises the possibility that life, if it ever existed, may have had more time to evolve on the Red Planet.