The Rio Scale of Extraterrestrial Contacts

IAA SETI Permanent Committee: Rio Scale (Iván Almár and Jill Tarter, in the 51st International Astronautical Congress, 29th Review Meeting on the Search for Extraterrestrial Intelligence, in Rio de Janeiro, Brazil, in October, 2000) is a scale for assessing putative contacts with extraterrestrial intelligent entities. It was devised in analogy with several other such scales, and the higher a putative contact scores, the greater is its importance.

Type of Phenomenon	(6) Earth-specific message, or an ET artifact, capable of contact, or a physical encounter (5) Omnidirectional message with decipherable information, or a functioning ET artifact or space probe (4) Earth-specific beacon to draw our attention, or an ET artifact with a message to mankind (3) Omnidirectional beacon designed to draw attention, or an ET artifact with a message of a general character (2) Leakage radiation, without possible interpretation, or an ET artifact the purpose of which is understandable (1) Traces of astroengineering, or any indication of technological activity by an extant or extinct civilization at any distance, or an ET artifact, the purpose of which is unknown
Method of Discovery	(5) SETI/SETA observation; steady phenomenon verifiable by repeated observation or investigation (4) Non-SETI/SETA observation; steady phenomenon verifiable by repeated observation or investigation (3) SETI/SETA observation; transient phenomenon that has been verified but never repeated (2) Non-SETI/SETA observation; transient phenomenon that is reliable but never repeated (1) From archival data; a posteriori discovery without possiblity of verification
Distance	(4) Within the Solar System (3) Within a distance which allows communication (at lightspeed) within a human lifetime (2) Within our Galaxy (1) Extragalactic
Reliability	(4) Absolutely reliable, without any doubt (3) Very probable, with verification already carried out (2) Possible, but should be verified before taken seriously (1) Very uncertain, but worthy of verification efforts (0) Obviously fake or fraudulent

Scores

Quality	Score
Type
Method
Distance
Total

Overall	Score
Quality
Reliability
Total

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