Spheres Spark New Martian Mystery

“This is one of the most extraordinary pictures from the whole mission,” Cornell astronomer Steve Squyres, the rover mission’s principal investigator, said today in a news release. 

The golf-cart-sized Opportunity rover used the microscopic imager on the end of its robotic arm to take a super-close look at the spherical shapes. These particular berries, measuring as much as one-eighth of an inch (3 millimeters) in diameter, cover an outcrop called Kirkwood in the Cape York segment of Endeavour Crater’s western rim. 

“Kirkwood is chock full of a dense accumulation of these small spherical objects,” Squyres said. “Of course, we immediately thought of the blueberries, but this is something different. We never have seen such a dense accumulation of spherules in a rock outcrop on Mars.” 

Iron-rich Martian blueberries first came to light soon after Opportunity headed out from its landing site on Mars’ Meridiani Planum in early 2004. The fact that they have layers of a mineral called hematite suggests that the spherules were formed by the action of mineral-laden water percolating through rocks. That’s how similar spherules formed on Earth, where they’re known as thunderballs, shaman stones or Moqui marbles. 

Since then, Oppy has run across the blueberries (which are actually gray) many times. A couple of years ago, the rover spotted an unusual spread of blueberries that were so tightly packed that scientists called it a “blueberry sandwich.” 

Some scientists say the berries could become important in the search for signs of life on Mars: In the August issue of the journal Geology, researchers from the University of Nebraska and the University of Western Australia contend that microbial activity played a part in the formation of iron spherules on Earth – and may have played a similar role on the Red Planet. Spherules with an iron-rich exterior and an iron-poor core could “offer a macroscopic target in the search for life on Earth as well as Mars,” they wrote.