Unusual Spherules on Mars

Explanation: What are those unusual spherules on Mars? The Mars Opportunity rover has now photographed several unusual nodules on Mars that have a nearly spherical shape. Many times these spherules are embedded in larger rock outcroppings but appear grayer. Pictured in the inset is one such spherule embedded in a rock dubbed Stone Mountain, visible to the Opportunity rover now rolling inside a small crater on Meridiani Planum . Opportunity was directed to go right up to Stone Mountain to get a better look. The inset picture spans only 3 centimeters across, revealing the rock to be named more for shape than actual size. Scientists are currently debating the origin of the spherules . One leading hypothesis holds that the beads were once-molten rock that froze in mid-air after an impact or a volcanic eruption. Another hypothesis holds that the spherules are concretions , hard rock that slowly accumulates around a central core. Opportunity will work to solve this mystery and others over the next few days.