The Unusual Blueberries at Bylot Rock

Why aren't these Martian rocks round? Small rocks dubbed blueberries have been found by the Opportunity rover all over Meridiani Planum on Mars , but the ones perched on Bylot rock have unusually non-spherical shapes. The strangely shaped blueberry rocks are shown above in an image taken by Opportunity's microscopic imager on August 9. Dark sand also covers much of Bylot rock . One hypothesis for the lack of blueberry roundness here is a coating relatively resistant to erosion. The average diameter of a blueberry is about 4 millimeters. The study of these and other rock features is allowing a better understanding of the wet past of ancient Mars.