I just had a question about angular momentum and linear momentum, which is probably best illustrated with an example.

Imagine a universe with a perfectly spherical asteroid of mass M, on which is firmly attached a massless cannon, pointed in a direction tangential to the surface of the asteroid. In the cannon is a cannonball of mass m. If the cannon fires the cannonball with a velocity v, giving it momentum mv, how exactly is the motion of the asteroid described? I can only assume it is given both linear and angular momentum, but how exactly do you determine how much of each? Can angular momentum ever take the place of linear in the law of conservation of momentum?