Phobos

The inner moon

The larger of Mars’s two moons, with an irregular shape.

Educational illustration · shapes and sizes are not to scale.

Orbiting: Mars
Category: Natural satellite

What makes this world interesting

It orbits Mars about three times a day and is slowly moving closer to the planet. Its origin remains under study.

Observe or explore it

Very difficult to distinguish close to Mars’s glare; spacecraft images are better suited to exploring its terrain.

Connect the discoveries

Mars

Sources and reference information

NASA Science — Phobos

Rounded educational data, sources consulted on 18 October 2026. Orbital distances are mean reference distances from the Sun, not current distances from Earth. Periods are expressed in Earth time. The planner provides date-specific positions for supported targets.