Possible evidence spherules formed by water
Nothing certain yet by any means:
...if the spheres have concentric shells, that would be a strong indicator of formation by percolating water. Some broken spheres have already been seen in the images, providing targets for even closer inspection. Also, analysis of the layering itself, if it shows ripples or certain kinds of crossbedding, could also reveal formation in water.
Tim Parker, a NASA-JPL geologist on the rover science team, says there are already some hints of concentric layering in the broken spheres. But the implications of such a find could be so significant that it will require far better imaging and analysis before reaching any firm conclusions.