NASA's Opportunity rover has discovered a peculiar rock on Mars that scientists think originated deep within the red planet. The stone could reveal new secrets about the makeup of Mars' interior. Dubbed “Marquette Island,” the rock is a dark boulder not much bigger than a basketball that sits on a rippled Martian plain. “Marquette Island is different in composition and character from any known rock on Mars or meteorite from Mars,” said Opportunity principal investigator Steve Squyres of Cornell University in Ithaca, N.Y. “It is one of the coolest things Opportunity has found in a very long time.” In all of its 11 miles worth of traveling, Opportunity has found only one other rock of comparable size to Marquette Island and scientists think it was ejected from a distant crater. Called “Bounce Rock,” that stone closely matched the composition of a meteorite that landed on Earth, but was thought to have originated on Mars. The coarse-grained texture and basalt composition of Marquette Island indicates that it cooled slowly from molten rock, allowing crystals time to grow. That means that it likely originated deep in the crust, not at the surface where it would cool quicker and have finer-grained texture, scientists say.
