'Yellowknife Bay' veins and concretions

In enlargements taken by the Mast Camera of NASA's Curiosity Mars seen here on the right, white arrows point to veins, and black arrows point to the small spherical concentrations of minerals called concretions in a low-lying dry stream bed named "Yellowknife Bay." Both veins and concretions strongly suggest precipitation of minerals from water. Curiosity's team decided to focus here for a first drilling target because orbital observations have shown fractured ground that cools more slowly each night than nearby terrain types do.