White Boat Rock on Mars

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 . Spirit resumed scientific operations two weeks ago after recovering from a computer memory problem . Spirit and its twin rover Opportunity , on the other side of Mars, continue to roam the red planet in search of clues to the ancient past of Earth's most hospitable neighbor .