Now that solar conjunction is over so that communication between Earth and Mars is no longer blocked by the Sun, NASA's Mars Exploration Rover Spirit is continuing its trek through the "Columbia Hills" in Gusev Crater. Straight ahead, in the foreground of this image, is a horizontally layered rock dubbed "Tetl," which scientists hope to investigate. Layering can be either volcanic or sedimentary in origin; researchers aim to determine which of these processes created this rock. If for some reason this particular rock is not favorably positioned for grinding and examination by the toolbox of instruments on the rover's robotic arm, Spirit will be within short reach of another similar rock, dubbed "Coba," just to the right, toward the middle of this image. Spirit took this image with its navigation camera on its 263rd martian day, or sol (Sept. 28, 2004).