16. These spheres look like a blueberry patch.
Another great Mars mystery is the discovery of spheres on the Red Planet. Known as blueberries, these small, round objects are among many round, smooth stones found on the surface of Mars. The Opportunity rover discovered the first patch of blueberries near its landing site shortly after arriving in 2012.
The Blueberries get their name from their blue hue, which is caused by their iron-rich nature. The chemistry of these rocks could indicate that at one point, Mars was an incredibly wet planet. Scientists are working to figure out how the blueberries were formed to see what sort of life, if any, once resided on the Red Planet. Research is being done in Utah and Mongolia, where rock formations similar to Martian blueberries have been discovered to study their origins further.