From publisher blurb:
This is an adventure for Cepheus Engine.
Rogue asteroids are discovered, on occasion, traveling through the Sonora sector. Normally these rogues are of no concern unless they are on a path to strike a populated world. These dangerous rogues are then deflected with a nuclear missile or destroyed more carefully with a planted nuclear device.
Recently, however, an asteroid has been discovered which has an alien base built into the side of it. This asteroid is traveling at high speed and is on course to strike the capital of one of the sub-sectors in the Sonora. A scientist contacts the travelers with a mission to visit this base and make sure that no living being is present before planting a nuclear device to shatter the asteroid. He offers substantial payment as well as the opportunity to find valuable alien artifacts at the base.