If you were wondering whether or not Martians played ball sports, NASA might have an answer for you.

According to a recent CBC News report, NASA’s curiosity rover has located a spherical rock on the surface of Mars. The rock, found in a region of Mars known as the Gale Crater, is about a centimeter wide. Curiosity sent back photos of the rock on September 11, as part of a stream of pictures collected from the area.

Apparently, this is not the first time that exploratory Mars rovers have located sphere-shaped rocks on the planet’s rocky surface. In 2004, NASA’s Opportunity rover found a whole cluster of them, all composed of a mineral known as hermatite. In 2012, Opportunity stumbled upon another collection of tiny spheres, though these were of different mineral composition.

It is conjectured that these ball-shaped rocks were created through a process known as concretion. According to CBC News, concretion occurs when minerals “precipitate within sedimentary rock,” forming mineral clusters in the shapes of spheres or ovals. The sedimentary rock erodes over time, whether because of wind or water, and the tightly packed balls of minerals are what is left behind. Concretion also occurs on Earth.

Because concretion is tied to water, it is possible that the appearance of these sphere-shaped rocks on Mars could be evidence that there was once water on the planet. However, some scientists are more satisfied with another theory, which states that the concreted spheres are the remains of meteors that once broke up in the Martian atmosphere.

As for why Curiosity found just one ball-shaped rock instead of a grouping of them, that is hard to say. Perhaps there is a tiny Martian somewhere in the Gale Crater still looking for his golf ball.