It looks like Gale Crater has its advantages.
‘Research suggests habitable conditions in the Yellowknife Bay area may have persisted for millions to tens of millions of years. During that time rivers and lakes probably appeared and disappeared. Even when the surface was dry, the subsurface likely was wet, as indicated by mineral veins deposited by underground water into fractures in the rock. The thickness of observed and inferred tiers of rock layers provides the basis for estimating long duration, and the discovery of a mineral energy source for underground microbes favors habitability throughout.’
You can also watch a 12/05/13 press briefing from JPL discussing those papers above. These rocks are much newer than the older wet period theorized.
They’re more focused on the search for organic carbon, now, within the environments they’ve discovered.