When NASA’s Curiosity rover was rolling along an area in lower Mount Sharp known as the ‘Old Soaker' in December, it came upon rock slabs bearing cross-hatched markings that may have originated as mud cracks.

When NASA’s Curiosity rover was rolling along an area in lower Mount Sharp known as the ‘Old Soaker' in December, it came upon rock slabs bearing cross-hatched markings that may have originated as mud cracks. 
According to a recent press release by NASA, if that does end up being the case, "...these would be the first mud cracks confirmed by the Curiosity mission. They would be evidence that the ancient era when these sediments were deposited included some drying after wetter conditions."
Determining the formation history of the cracks will rely heavily upon an analysis of their contents. 
The agency notes, “Cracks that form at the surface, such as in drying mud, generally fill with windblown dust or sand. A different type of cracking with plentiful examples found by Curiosity occurs after sediments have hardened into rock. Pressure from accumulation of overlying sediments can cause underground fractures in the rock. These fractures generally have been filled by minerals delivered by groundwater circulating through the cracks, such as bright veins of calcium sulfate.Both types of crack-filling material were found at Old Soaker...This may indicate multiple generations of fracturing...” 
Ashwin Vasavada, a scientist on the Curiosity team, said, "If these are indeed mud cracks, they fit well with the context of what we're seeing in the section of Mount Sharp Curiosity has been climbing for many months. The ancient lakes varied in depth and extent over time, and sometimes disappeared. We're seeing more evidence of dry intervals between what had been mostly a record of long-lived lakes."