Asteroids are large rocks found randomly in systems. Each may contain a number of resources, either standard planetary resources or resources special to asteroids. Once a mine has been constructed by a planet at a particular asteroid, the resource it produces may be exported to other planets or orbitals as normal.
To construct an asteroid mining base, select a planet with labor generation and right click the asteroid. Select the type of mining base you wish to construct from the right click menu.
Asteroids appear in a random quantity (1 to 4 asteroids apparently) after a planet has been destroyed, by a Buster machine for example.
Asteroids may contain three classes of resource: Planetary, Permanent, and Temporary.
Planetary resources are any resource normally found on planets. Unlike planets, asteroids may produce these resources without importing typical level requirements.
Permanent and temporary resources are asteroid-specific resources with special utilities unavailable on planets. Temporary resources will be quickly used up when exported to destinations that are able to make use of them. The labor cost of asteroid base construction increases by 50% for every system between the constructing planet and the target asteroid.
Some asteroids will be useful only for their raw ore, rather than providing any more advanced resource. Ore is mined by mining ships and dropped off at planets to be used to build massive constructions.