If they're not real blueberries, then what are those blueberry-esque iron spheres on Mars? And could they help tell the story of the planet's ancient past?
Researchers initially suspected that the "Mars blueberries" might yield evidence of ancient water (and therefore, ancient life) on the planet. But now it appears that the hematite balls might simply be remnants of meteorite and are only a few years old.
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This image provided by NASA shows loose, BB-sized, hematite-rich spherules embedded in this Martian rock (like blueberries in a muffin) and released over time by erosion.
The Martian blueberries were discovered by NASA's Opportunity rover in 2004.
A popular theory, described in a study published in June 2012, held that the blueberries formed as a result of the flow of water through rocks on the planet -- the same way similar iron-rich spheres are formed on Earth. But researchers from the Hawaii Institute of Geophysics and Planetology now believe that the spheres formed from meteorites that broke up in the Red Planet's atmosphere.
Their findings were published earlier this month in the journal Planetary Space and Science.
Misra and his colleagues say their new theory is supported by the fact that the blueberries are much smaller than similar minerals typically are on Earth. According to National Geographic, the Martian blueberries range in size from about 0.16 inch in diameter to 0.24 inch. Additionally, they say, the wear seen on the Martian blueberries suggests that they aren't ancient.
An example of comparatively large spheres found on Earth. Located on a beach in Mendocino County, Calif., these objects were weathered out of ancient mudstone.
But if the blueberries don't show evidence of liquid water on Mars, previous research suggests that water once flowed on the Red Planet. There may even be water flowing on Mars now. Earlier this month, scientists indicated that mysterious streaks that appear on the planet's surface may be evidence of flowing water.
Clarification: This story has been updated to reflect that the study published in Planetary Space and Science represents one viewpoint in the scientific community.