NASA’s Curiosity rover has discovered remains of sediments from lakes along the foothills of Mount Sharp, a finding that yields clues to ancient Mars. Scientists believe that the sediment remains are from lakes that once filled the deep bowl, likely tens of millions of years ago. It wasn’t until much later that winds carved out the roughly three mile high peak that is visible today.

Such a finding is significant as it shows that past climates on Mars were likely much warmer and wetter in its first two billion years of life than was previously believed. Curiosity’s team suggests that this recent discovery points to a cycle with rain or snow to keep up such humid conditions. There is also the possibility that the planet may have even had an ocean on its surface.

Dr. Ashwin Vasavada, a Curiosity deputy project scientist, said in a statement, “If we have a long-standing lake for millions of years, the atmospheric humidity practically requires a standing body of water like an ocean to keep Gale from evaporating.”

Craters such as Gale are often characterized by central mounds formed when the ground rebounds following an impact from an asteroid or comet, which forms a bowl. However, the sheer size of Mount Sharp is too big to fit this explanation.

One of the mission’s most critical discoveries is the inclined sediment beds, which the rover indicated were faced towards towards down the mountain.

According to the NASA Jet Propulsion Laboratory, studying Gale Crater from orbit shows that the layers have different minerals depending on their height. Near the bottom of the mound are clay minerals. Above the clay-bearing layers are layers with sulfur and oxygen-bearing minerals are above them.