The Opportunity rover, which landed on Mars in 2004, found numerous small hematite spheres, each about 3 mm in diameter, on an outcrop called Kirkwood. Researchers have never before seen such a high concentration of spheres like these on Mars. These iron-rich balls are similar to the Martian “blueberries” the rover first saw in 2004, but closer inspection reveals that they are not. The “blueberries” that were discovered in 2004 are concretions that formed when minerals from water settled into sedimentary rock (this provided evidence that the Red planet once had liquid water). Compared to the “blueberries”, the spheres contain less iron. Researchers say that the spheres found on Kirkwood, when broken open, have concentric circles on the inside. Squyres from NASA stated that the iron spheres appear to be crunchy on the exterior and soft on the inside.
Such iron-rich spheres are often found on Earth in deserts and beaches. In fact, a notable example of a place where they are found is the Jurassic Navajo Sandstone situated near the Colorado River in Utah, where the hematite spheres may be as small as marbles or as large as cannonballs. Interestingly, these iron spheres have a hard iron oxide exterior and have a soft sandy interior, much like the “blueberries” found on Kirkwood.
It is uncertain how the spheres on Kirkwood were formed. One concept of their existence was that they formed as a result of simple chemical reactions, but UWA researchers have suggested otherwise. When they used the NanoSIMS (structured illumination microscope), they showed that there is a relationship between microbe-like forms and elements such as nitrogen and carbon in the concretions at Utah. Microstructures in the Utah spheres are similar to the residue of certain bacteria. The “blueberries” possibly contain more proof of life on Mars. NASA says that the Opportunity Rover will keep studying these mysterious spheres during the following weeks.
