Artifacts (or Library Nodule Artifact, as they are known to the Progenitors) are mysterious and unexplained Progenitor devices sometimes discovered on Planet. If you can find an artifact and return it to one of your bases, you will have several options: (a) you can link it to a Network Node if you have one, and receive a free technology breakthrough; (b) you can use it to speed the production of a Secret Project or Unit Prototype; (c) you can save it to use later.
Artifacts can be captured from other players. A lone artifact can be captured by any player without diplomatic penalty.