The last time we checked in with the Mars Curiosity rover, it reached the base of Mount Sharp after two long months of slowly rolling across the Martian surface. The rover has been on Mars for a little over two years, and has so far gingerly traveled around 5.5 miles — in this case, it’s better to be slow and safe than reckless and sorry. Curiosity hasn’t found anything too out of the ordinary during its travels (if you don’t consider alien terrain out of the ordinary, that is); the weird images it captures mainly showcase some sort of illusion. However, this time around, the rover has found what appears to be a smooth ball sitting on the Martian surface.
The photo was taken with Curiosity’s Mastcam while creating a mosaic image of the landscape. It plainly shows a very spherical object sitting atop a comparatively normal flat outcropping. The spherical rock also appears to be darker in color than other nearby rocks, though it also seems to be covered in dust. It looks like it could be an artificial object, but it’s not. In fact, the perspective of the picture is misleading — the spherical stone isn’t the size of a golfball like it looks. Instead, it’s about one centimeter wide.
According to NASA’s Jet Propulsion Laboratory, the little sphere is likely a concretion. Pores are created when sedimentary rock is forming — something that happened on Mars back when it contained water — and minerals filled in the pores. After a while, the sedimentary rock erodes, leaving behind the concretion.
Concretions aren’t always spherical, but they tend to be.
The spherical stone on Mars could have simply appeared after sedimentary rock eroded, or, considering it’s spherical, it could’ve rolled from somewhere else over time. Check out a high-res image of the rock below.
It’s fun that Curiosity continues to find seemingly wacky things on Mars, but it’s not fun that it turns out to be regular old science.