NASA's Curiosity rover has spotted clear signs that Mars experienced seasonal wet-dry cycles some 3.6 billion years ago, a discovery that bolsters the evidence that the planet was once hospitable to life, reports a new study.

In 2021, Curiosity drove by a patch of strange polygonal ridges that had never been seen on Mars before. Scientists have now concluded that the patterns are cracks formed by regular episodes of flooding and drying, a natural phenomenon that is known to be extremely conducive to life here on Earth. 

Curiosity, which has been exploring an area called Gale Crater since 2012, has already amassed an enormous body of evidence that shows ancient Mars hosted was habitable to life as we know it. The fossilized cracks, formed in fresh mud, reveal that "repeated wet–dry cycles of regular intensity" could have created "an Earth-like climate regime and surface environments favorable to prebiotic evolution" on Mars, according to a study published on Wednesday. 

"The pattern was striking," said William Rapin, a CNRS research scientist at the Institut de Recherche en Astrophysique et Planétologie in Toulouse, France, who led the new research, in a call with Motherboard. "It's quite a unique formation. It's the first time we've seen that on Mars, actually, and it tells us a lot of details on how the climate was working at the time." 

"We've seen riverbeds and lakebeds," he added, referring to Curiosity's observations. "But the modality of how the climate was working was still a puzzle. Now, we see this pattern of cracks that really tells us there had to be seasons, a wet season and dry season, in a very regular fashion."