In all cases, there is no guaranteed method of acquiring an artifact. Each applicable method only has a random chance of providing an artifact, in addition to normal rewards. For each artifact category, there is base acquisition rate: * Old Earth: 20% * Alien: 38% * Progenitor: 55% After each expedition or destroyed nest, if no artifact was acquired, the acquisition rate for corresponding category is increased: * Old Earth: +10% * Alien: +7% * Progenitor: +3%