Armed with more sophisticated analysis tools than earlier rover teams, Curiosity scientists have been able to conclusively find the first on-the-ground evidence for the presence of abundant clay minerals within those drilled rocks.
Using filters on the rover's Mast camera (Mastcam) and an instrument which shoots neutrons into the ground to probe for hydrogen, researchers have detected more hydrated minerals near the clay-bearing rock than at locations Curiosity visited earlier in its mission.