A banner day for the Mars rover Curiosity, as it conducted its first drilling beneath the surface layer of a martian rock today. The hope is to gain information about long-past, possibly wet environments on the red planet by taking samples from beneath its surface – in this case, 2.5 inches deep. The rock powder generated from the drilling was saved by the Curiosity, and will be analyzed by its highly sophisticated on-board laboratory. (Photo by  NASA/JPL-Caltech/MSSS) source