Looking at the shadow - Sol 666

Original caption:"Spirit is healthy and making good progress downhill. The Rover performed an extensive campaign with the tools on the RA at an outcrop called 'Larry's Bench' and made targeted observations with other instruments.
The team has been taking advantage of every drive sol, averaging about 40 mt (131 feet) per sol.
Mars is currently passing through a debris trail of Halley's comet, and Spirit is attempting to observe resulting meteor showers with the PanCam at night".