White Boat Rock on Mars . ... Credit Copyright: Mars Exploration Rover Mission , JPL , NASA Explanation: What caused this rock to have an unusual shape? Earlier this month the robot Spirit rover on Mars stopped to examine a rock dubbed "white boat", named for its unusually light color and shape. White boat, the large rock near the image center of the above color-composite image , was examined by Spirit just after Adirondack , a football-sized rock determined to be composed of volcanic basalt . ...