NASA’s Curiosity rover recently examined slabs of rock that, if interpreted correctly, would be the first mud cracks confirmed by the mission. This would confirm that some drying occurred after wetter conditions in the ancient era during which these sediments were deposited.
The rock slab in the image is known as “Old Soaker,” and the image is about three feet from left to right.
These cracks were discovered on lower Mount Sharp inside of Gale Crater, the location of Curiosity’s landing back in 2012. The mission previously found evidence of ancient lakes in both older rock layers and younger mudstone.
With the formation of the cracked layer occurring more than 3 billion years ago that was then buried by sediment layers, the whole thing became stratified rock. Later erosion due to wind took away the layers above Old Soaker.
Inside the cracks, material was found that was more effective at resisting erosion than the mudstone around it, causing the appearance of raised ridges.
What types of material filled the cracks?
One type was windblown dust or sand – the kind of material that normally fills cracks that form at the surface.
One type of cracking was one that had been found many times before by Curiosity. It is created after sediments have hardened into rock, and the pressure of the sediments can cause underground fractures in the rock. What generally fills these fractures? Minerals that are delivered by groundwater which circulates through the cracks.
With both kinds of these materials found to be filling cracks at Old Soaker, there’s a possibility that mud cracks may have occurred first, been filled with sediment, and then underground fracturing and the forming of veins occurred. This could indicate more than one generation of fracturing.
The cracks that are likely to have been caused by drying are not the only kind of evidence found in the area; sandstone layers were found that were interspersed with mudstone layers. A pattern called cross-bending was also found. This is meaningful because the pattern can form where water flowed more vigorously near a lake shore or sediment was blown by the wind during a dry episode.
The data from the possible mud cracks continues to be analyzed by scientists. They are also keeping their eyes open for sites that look similar to search for clues that were not found at Old Soaker.
In its mission on Mars, NASA’s Curiosity rover continues to build upon a successful past as it brings us new and meaningful discoveries. Now, the rover is looking into how and when the conditions changed from old habitable conditions to be dryer and less supportive of life. The mission previously found evidence of ancient Martian lakes offering conditions favorable for microbes if Mars has had life on it.
Learn more about the Curiosity mission at NASA.gov.