What’s That Musket Ball Doing On Mars?

Certainly catches the eye, doesn’t it? The spherical rock was photographed on September 11, 2014 by the Curiosity rover. It’s about a half-inch across and according to NASA scientists probably a concretion. Credit: NASA/JPL-Caltech/MSSS

It looks ever so much like an early 18th century musket ball, but the chances of soldiers traipsing around Mars a couple hundred years ago seems unlikely. Even if it’s the god of war. NASA’s Curiosity rover snapped this photo during a routine round of landscape imaging on September 11th.

There’s nothing like seeing a near-perfect sphere on another planet to make you sit up and wonder. First off, it’s not as big as you might think, measuring just under 1/2 (1 cm) in diameter or about the size of a marble. Second, we’ve seen spheres on Mars before – zillions of them!

Tiny “blueberries” in the Martian soil near the rock outcrop at Meridiani Planum called Stone Mountain. While other ideas have been proposed for their formation, water trickling through rocks to build concretions remains a strong possibility. Credit: NASA/JPL

The Mars Opportunity rover found countless spheres, nicknamed Martian “blueberries”, during  its exploration of Meridiani Planum. If you could hunker down for a look, they’d remind you of BBs from a  BB gun with diameters of .16 to .24 inches (4-6 mm). The spheres contain large amounts of hematite, an iron-bearing mineral, that most likely originated as concretions in layers of sedimentary rock that have since eroded away.

Groundwater moving through porous rocks can dissolve iron-containing minerals which then precipitate out as small, compact spheres. Concretions on Earth, such as Moqui balls and Kansas Pop Rocks, are considerably larger than the Martian variety, but that may be due to the different environments of the two planets. 

So our mystery sphere is probably a larger-than-usual concretion, freed from its rock stratum by wind and perhaps water erosion and now served up on a plate for Curiosity’s and eyes.

To view more pictures of the weird sphere, click HERE and scroll down toward the bottom for the Mastcam color images.

7 Responses

    1. astrobob

      I’m not an expert but it does resemble the ball maybe at an earlier stage before being eroded from the matrix. Cool!

Comments are closed.