If a terrestrial size planet or moon has a base (not surface) temperature between -130C and +120 C there is a 5% chance it may have 'ruins' of a past civilization. These ruins are discovered as a result of a system body survey and can be one of the following 5 types.
1-50 Scattered Ruins. Tech Chance 20%, Exploited 50%
51-75 Significant Ruins. Tech Chance 40%, Exploited 40%
76-90 Extensive Ruins. Tech Chance 60%, Exploited 30%
91-97 Damaged Alien Installation TC 75%, Exploited 25%
98-100 Intact Alien Installation. TC 100%, Exploited 20%
The Tech Chance is the annual chance of a random tech being found by an Archaeological Team working on the site. This random tech will be something that the race could research given its current capabilities but research cost is not a factor so an expensive tech is just as likely as a low cost one. The annual chance is multiplied by the Team Rating/100. So for a Team with a rating of 60, the annual chance of finding a random tech in Extensive Ruins is 15% x 60/100 = 9%. As time usually passes in small fractions of a year, the chance is reduced accordingly.
Example: If 5 days passed, the chance of a Team with a rating of 60 working in Extensive Ruins discovering a tech during those five days is 15% x 60/100 = 9%. x 5/360 (360 days in an Aurora year) = 0.125% (or one eighth of one percent).
The Exploited percentage is the annual chance that all major secrets have very likely been found and it was take a lot of work to uncover anything else. Once ruins are exploited there is only 1/10th of the previous Tech Chance but the chance will get never lower than this. After a race has exploited ruins it can therefore continue searching with a low, but better than nothing, chance of success.
A ruin is in one of three states: Undisturbed, Signs of Activity and Exploited. As soon as any race lands a science team on Undisturbed Ruins, they become ruins with Signs of Activity. This does not affect the Tech Chance but it does allow other races to know someone has been there. It is quickly obvious to a science team if ruins have merely Signs of Activity or if they are Exploited.
When a ruin is discovered a Ruin Race ID is assigned to it, which is a random number from 1-100. A name is also created for the extinct race. Every time a race discovers a technology from an extinct race, they gain a 10% bonus to their Tech Chance in all ruins for that same race for future rolls. This bonus represents growing knowledge of an extinct race and is cumulative.
Example: If a race had discovered four technologies from an extinct race called the Kingdom of Zog and were exploring a Zog Extensive Ruin using an Archaeology Team with a rating of 70, their annual tech chance would be as follows. 15% (base chance for Extensive Ruins) x 0.7 (Team Rating) x 1.4 (40% bonus for four technologies) = 14.7% per annum
A race can have more than one Archaeological Team allocated to a planet with ruins. Each team checks individually so the chance of finding tech increases but the chance of the ruins becoming exploited is rolled once for each team. As the chance of finding tech is modified by the skill of the team but the chance of exploitation isn't, this means that assigning a lot of unskilled teams means the ruins could become quickly exploited without a high chance of finding anything useful.
Example: If you had one team with Skill 90 and three with Skill 30 working on Significant Ruins (Tech Chance 10%, Exploit Chance 25%), the annual chance of finding tech would be 9% for the first team and 3% for each of the other teams. However, the 25% annual chance of the ruins becoming exploited would be rolled once for each team.
When an Archaeological Team finds tech, the skill of that team increases by 1-10 points to reflect an increase in their experience