The Cosmic Bomber — William F. Wu

Time is running out. Thomsen 4, a small Earth-like planet, is on a collision course with a speeding comet, and the impact will wipe out the Arrs, a lupoid race of unknown intelligence. But Dr. Bones and his crew discover they aren't the only ones with a stake in the fate of Thomsen 4. The more they dig into the planet's history, the more sinister the evidence becomes.