Martian ‘Blueberries’
In 2004, NASA’s Opportunity rover explored an area at Meridiani Planum where the surface was covered with unusually round gray pebbles. NASA scientists saw “strange round objects we’re calling ‘spherules’ embedded in the outcrop, like blueberries in a muffin,” said Steve Squyres, member of the Mars Exploration Team, at the time. The balls varied in size, ranging from 100 micrometers to 602 millimeters in diameter.
Some 16 years later, scientists remain in disagreement about these so-called “blueberries,” but they’re (probably) not biological in nature. Prevailing theories include hematite concretions formed from water, spheres produced by meteorite impacts (i.e. accretionary lapilli), and balls that formed from calcite minerals.
