The National Geographic reported on Feb. 24 that scientists believe the "blueberries" NASA's Opportunity rover found on Mars in 2004 are not geological evidence of ancient water.

The countless gray-blue spherical rocks Opportunity found on the Martian surface are now believed to be meteorite remnants that broke up when entering the red planet's atmosphere.

Upon the discovery of the "blueberries'" presence, which have large amounts of hematite, an iron-bearing mineral, scientists theorized numerous explanations including shockwaves from meteor impacts or volcanic eruptions.

The most popular theory from the discovery team, which led most scientists to believe for the last decade, was based on a natural occurrence that happens on earth. When groundwater flows through porous rocks, hematite spheres emerge from a chemical reaction causing iron minerals to precipitate into tiny spherules.

The theory suggested that water flowed on Mars in ancient eons.

However, according to the "Planetary and Space Science" journal, University of Hawaii scientists argue the meteorite theory is a better explanation the "blueberry" rocks' presence.

The study's lead geophysics researcher Anupam Misra said the narrow size of the spherules cannot be explained by the concretion model, which is the biggest issue in proving they are related to the planet's ancient water.

"None of the physical properties of the spherules match the concretion model," Misra said. "But the meteorite theory explains all of their properties."

Misra argued that the spherules range between .16 inches and .24 inches in diameter but Earth's spherules are typically much larger. She said the small meteorite theory makes sense because just a few impacts could shower the large area with an abundance of .16-inch spherules.

In addition to the study's theory debunking the "blueberries'" origin, the researchers believe the spherules are not eons old but rather relatively new based on the shininess of some of the rocks, which suggest it hasn't experienced a lot of physical weathering.

University of Utah geologist Brenda Bowen argues, however, that just because the spherules are smaller and still glimmer, doesn't mean they're either new or came from concretion.

There are some pretty gross inaccuracies about what they're claiming," Bowen said.

The sizes can vary and are not limited to earth's standards because the environments are different and water availability could have had a role in the "blueberries'" formation, Bowen said. Furthermore, she argues that concretions on earth can also produce shiny spherules, as well as spherules coated with dust and sand.

"When the wind blows, you can get this kind of polishing from abrasion," Bowen said.