The network of cracks in this Martian rock slab called "Old Soaker" may have formed from the drying of a mud layer more than 3 billion years ago. The view spans about 1.2 meters left-to-right and combines three images taken by the Mars Hand Lens Imager (MAHLI) camera on sol 1566 (December 31, 2016). Mud cracks would be evidence of a time when dry intervals interrupted wetter periods that supported lakes in the area. Curiosity has found evidence of ancient lakes in older, lower-lying rock layers and also in younger mudstone that is above Old Soaker. The bright veins are filled with calcium sulfate. They likely formed after the sediment had already turned to rock, suggesting more than one generation of fracturing. For more information, visit JPL's website.