Images and data from Martian cliffs show the first evidence of rivers that existed on the Red Planet 3.7 billion years ago, according to researchers.
The images came from NASA's Mars Reconnaissance Orbiter's HiRISE camera. The scientists focused on the Hellas Basin, a large impact crater, in Mars' southern hemisphere.
The rocks in the impact crater show evidence that Mars was able to sustain different types of bodies of water because they are similar in appearance to rocks on Earth that were formed by rivers, said a study in the journal Nature Communications.
The exposed cliff faces reveal "rivers that continuously shifted their gullies, creating sandbanks, similar to the Rhine or the rivers that you can find in Northern Italy," the researchers said.
"We don't have the ability to climb, to look at the finer-scale details, but the striking similarities to sedimentary rocks on Earth leaves very little to the imagination," said study author Francesco Salese, a geologist at Utrecht University in the Netherlands and a senior scientist at the International Research School of Planetary Sciences in Italy.
The researchers concluded that the rivers were about 9 or 10 feet deep after examining sediment layers. They also believe they found evidence that sustained its water presence through precipitation, similarly to rain on Earth, which would have been necessary for any life-forms to survive on the planet.
"Such perennially flowing rivers would require an environment capable of maintaining large volumes of water for extensive time periods, and almost certainly necessitated a precipitation-driven hydrological cycle," Salese said. "[This is] more in line with slower climatic change, and less in line with catastrophic hydrologic events. This kind of evidence, of a long-lived watery landscape, is crucial in our search for ancient life on the planet."
