An anomaly is represented by survey readings that deviate from what is normal. When a science shipsurveys a celestial body it may identify an anomaly that needs further investigation. Anomalies have their own tab in the Situation Log.
When the investigation of an anomaly is complete, an event will pop up that can give various bonuses, such as research points, resources on a planet, or even a special project which requires further research investment to unlock benefits. Certain Ethics occasionally have additional options.
Each surveyed celestial body has a 5% chance of spawning an anomaly, which is increased by 0.5% for every surveyed planet with no anomaly before being reset. The Meticulous trait also increases the chance of finding anomalies by 10%.
To investigate an anomaly, a science ship with a scientist on board must be present at the celestial body where the anomaly is located. Investigating them takes time, which is determined by the level of the scientist minus the difficulty level of the anomaly. As such, anomalies of higher levels are often best left off until a skilled scientist can study them faster.
There are two types of repeatable anomalies. The first is the Ancient Signs of Life anomaly, which can only be found on Barren worlds and will add the Terraforming Candidate planet modifier once investigated.
The second are anomalies with the name randomized based on the planet class which will reveal a pre-sapient species on the planet once investigated. Such an anomaly can be triggered once for each planet class, including Gaia and Tomb worlds. Genocidal empires cannot discover these anomalies.
If the Sol system is present in the galaxy a random Asteroid might reveal a level 3 Debris Field Anomaly. Investigating it will discover the Pioneer 11 probe. If the empire is human it will gain 40-100 Influence. If the empire is alien on the other hand it will bring the following options:
Decipher the data disk and gain 120-250 Engineering Research while the science ship leader gains 200 Experience. The location of the Sol system is added to the situation log. Entering the system will grant 80-175 Influence.
Sell the data disk and gain 120-250 Engineering Research.
Use the data disk as furniture and gain 40-100 Influence if Xenophobe or Fanatic Xenophobe.