Mars, often called the Red Planet, has two small moons: Phobos and Deimos. Their names come from Greek words meaning Fear and Panic. Scientists believe these moons may once have been asteroids, possibly formed in the belt between Mars and Jupiter before being pulled in by Mars’ gravity.

This image shows Phobos, the larger of the two moons. Its rough, cratered surface makes it look more like a rocky asteroid than a typical moon. The picture was captured by NASA’s Mars Reconnaissance Orbiter, a spacecraft capable of photographing objects as small as 10 meters across.

Phobos orbits extremely close to Mars—only about 5,800 kilometers above the surface. For comparison, Earth’s Moon is about 400,000 kilometers away from us. Because Phobos is so close, Mars’ gravity is slowly pulling it inward. Over time, powerful tidal forces are dragging it closer and closer to the planet. Scientists expect that in about 50 million years, Phobos will likely break apart and form a ring of debris around Mars.

In a distant future, the Red Planet may have rings instead of this small, struggling moon.