Among other discoveries made by the rover, corrugated rock textures suggest lakes existed in an area of ​​ancient Mars that scientists expect to be drier. When NASA’s Curiosity rover reached the “sulphate unit” last fall, scientists thought they had seen the latest evidence that lakes once covered this region of Mars. This is because the rock layers here formed in drier conditions than in the areas discovered earlier in the mission. Sulfates – salty minerals – are believed to be left behind as the water dries out until it drips.

The Curiosity team were surprised to find the clearest evidence of the existence of ancient water waves in lakes. Billions of years ago, waves on the surface of a shallow lake stirred up the sediment on the lake floor and eventually formed ripples that remained in the rock.

“This is the best evidence of water and waves we’ve seen in the entire mission,” said Ashwin Vasavada, Curiosity’s project scientist at NASA’s Jet Propulsion Laboratory in Southern California. “We’ve been through thousands of feet of lake sediment and have never seen such evidence, and now we’ve found it in a place where we expected it to be dry.”

layers of history

Since 2014, the rover has climbed to the base of Mount Sharp, a 3-mile (5-kilometer) mountain that was once filled with lakes and streams that provided a rich environment for microbial life. formed on the red planet.

Mount Sharp is made up of layers, with the oldest at the base of the mountain and the smallest at the summit. As the rover rises, it moves along the Mars timeline, allowing scientists to study how Mars evolved in its ancient past from a more Earth-like planet with a warmer climate and abundant water to the cold desert it is today.

Curiosity found these protruding rock textures preserved in what’s called the “Marker Band,” a thin layer of dark rock that stands out against the rest of Mount Sharp, about 800 meters above the base of the mountain. This layer of rock is so hard that, despite several attempts, Curiosity was unable to extract a sample. This isn’t the first time Mars has been reluctant to share samples: under the mountain, on Vera Rubin Ridge, Curiosity had to try three times before finding a soft enough spot to pierce.

Next week, scientists will look for softer breeds. But even if they can’t get a sample of this offbeat rock band, there are other places they’re eager to explore.

Mars tips

Far beyond the Marker Strip, scientists can see another clue to Mars’ ancient water history in a valley called Gediz Vallis. The wind carved the valley, but the channel that runs through it and starts high above Mount Sharp is believed to have been eroded by a small river. Scientists suspect wet landslides have occurred here, too, sending car-sized boulders and debris to the valley floor.

It is clear that it is one of the youngest structures on Mount Sharp, as the pile of debris lies above all other layers in the valley. Last year, Curiosity had seen this wreck twice on the Gediz Vallis Ridge, but only viewed it from afar. The traveling team hope to get another chance to see it later this year.

Another clue that intrigued the team in the Signal Band was an unusual rock texture, possibly caused by some sort of regular weather or climate cycle, such as dust storms. They are rocks composed of layers with regular spacing and thickness, not far from grooved textures. Such a rhythmic pattern in rock layers on Earth is usually caused by atmospheric events that occur at periodic intervals. It is likely that the rhythmic patterns of these Martian rocks are the result of similar events that indicate changes in the ancient climate of the Red Planet.

“Wave rifts, debris flows and rhythmic layers tell us the history of the wet-to-dry transition on Mars is not simple,” said Vasavada. “Mars’ ancient climate had an astonishing complexity, similar to Earth’s.”