How were these unusual Martian spherules created? Thousands of unusual gray spherules , made of iron and rock but dubbed blueberries , were found embedded in and surrounding rocks near the landing site of the robot Opportunity rover on Mars . To help investigate their origin, Opportunity found a surface dubbed the Berry Bowl with an indentation that was rich in the Martian orbs . The Berry Bowl is pictured above , imaged during rover's 48th Sol on Mars. The average diameter of a blueberry is only about 4 millimeters. By analyzing a circular patch in the rock surface to the left of the densest patch of spherules, Opportunity obtained data showing that the underlying rock has a much different composition than the hematite rich blueberries. This information contributes to the growing consensus is that these small, strange, gray orbs were slowly deposited from a bath of dirty water .
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Credit: Mars Exploration Rover Mission , JPL , NASA