This picture appears to be dried mud on the surface of Mars
This picture was taken by the Mastcam on the Curiosity Rover. This area is now called the “squid cove”. The picture was modified so that it was white balanced. This means the rocks appear as how they would in daylight here on Earth, instead of how they actually appear on Mars. Making the rocks looks like how they would on Earth makes it easier for scientists to study the surface. [1]
Scientists found cracks in the dirt of this picture. The cracks most likely formed when the dirt was wet with water and then dried out. These cracks got filled with sediment from wind, which eventually turned to rock. As what was left of the mud eroded away ridges of the sediment are left, showing the cracks as ridges. These are not the only evidence of water on Mars, far from it. Rovers have found hydrated salts and recurring slope lineae. Hydrated salts most likely had to have liquid water to form, and recurring slope lineae (basically dark streaks that flow) show that water might still flow from time to time on the surface. [1][2]