NASA’s not quite sure what to think of a curious geological phenomenon that the aging Opportunity Rover came across last week on Mars. The formation looks like a rash of tiny spheres, each about three millimeters in diameter, but scientists have no idea how or why they formed. Opportunity snapped a few photos with its microscopic imager and used its alpha particle x-ray spectrometer (which sounds like the coolest tool ever) to analyze its composition. Puzzled as NASA may be, everybody is also very excited . Opportunity’s principal investigator, Steve Squyres of Cornell University called the picture of the spheres “one of the most extraordinary pictures from the whole mission.”
First of all, three cheers for the Opportunity rover, which was launched in July 2003 and has now exceeded all expectations with its mission length. Incredibly, this is actually the second time that the Opportunity has come across this sort of phenomenon. Back in 2004, the rover found a similar crop of spherules made up mostly of iron, which gives scientists more reason to believe that water once existed on the red planet. They believe spheres formed by mineral-rich water collecting inside of sedimentary rocks. As the rocks erode, the harder, spherical center made up of the minerals from the water — mostly iron — emerges. At the time, researchers called the curious formation “blueberries.”
These new spheres are different, though. “They seem to be crunchy on the outside, and softer in the middle,” Squyres said. “They are different in concentration. They are different in structure. They are different in composition. They are different in distribution. So, we have a wonderful geological puzzle in front of us. We have multiple working hypotheses, and we have no favorite hypothesis at this time. It’s going to take a while to work this out, so the thing to do now is keep an open mind and let the rocks do the talking.”
There is the possibility that the structures were actually formed by little bitty Martians. After all, similar spheres found on Earth and are attributed to the remnants of bacteria. In a paper published in Geology just two days before the latest find, researchers from the University of Western Australia said that the first batch of blueberries showed “clear evidence that microbes were essential in their formation.” They pointed to comparable spheres with a hard iron oxide shell and soft sandy interior found in the Jurassic Navajo Sandstone near the Colorado River in Utah which they classified as “microstructures consistent with bacterial size and morphology.”
NASA plans to gather more data with the Opportunity Rover as they try to figure out exactly what’s going on. It’s likely that these balls are exactly what they appear to be: a geological phenomenon. But it’s more fun if you just imagine that they were created by little green men as an art project.