Asteroid Belt

Quick facts

Object type: Region of small Solar System bodies

Distance note: Main-belt region approximately 2.2–3.2 AU from the Sun (about 329–479 million km; 204–297 million miles). There is no single average for the whole belt.

Diameter note: Not applicable: a region containing many separate objects.

Moons: Not applicable to the belt as a whole. Some individual asteroids have moons.

Year: Varies by object and orbit.

Rotation: Varies by object.

Solar day: Varies by object.

Gravity note: Varies by object; the belt has no shared surface.

Temperature: Varies with each object’s distance, illumination and surface.

Atmosphere / composition: Diverse rocky and metallic bodies, including carbon-rich and silicate-rich asteroids.

Rings: The belt is a population of objects orbiting the Sun.

Remember this

All the asteroids combined have less mass than Earth’s Moon.

Explore this world

The main belt preserves remnants of early planet formation. Its objects are widely separated, giving spacecraft plenty of room to travel between them. Ceres, a dwarf planet, and Vesta are two of its most massive residents.

What makes it distinctive

Each body has its own orbit, size and geology. The photograph shows Vesta, one member of the belt, rather than a view of the entire region.

Exploration

NASA’s Dawn mission orbited Vesta and Ceres, revealing very different histories.

Mission updates

Dawn’s archived observations remain a resource for studying these early worlds.

Mission information last verified: 2026-10-03

Image credit

NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

View the original image and its context

Sources and further reading

Image source and credit

NASA science and mission reference

NASA science and mission reference

Dawn image of Vesta and full credit

Science last verified: 2026-10-03

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