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. It uses this scale:
- 10: Extraordinary
- 9: Outstanding
- 8: Far-reaching
- 7: High
- 6: Noteworthy
- 5: Intermediate
- 4: Moderate
- 3: Minor
- 2: Low
- 1: Insignificant
- 0: None
Its value is calculated in this fashion:
(quality) * (reliability)
where
(quality) = (type) + (method) + (distance)
- Type:
- 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:
- 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
- Credibility or Reliability:
- 4/6: Absolutely reliable, without any doubt
- 3/6: Very probable, with verification already carried out
- 2/6: Possible, but should be verified before taken seriously
- 1/6: Very uncertain, but worthy of verification efforts
- 0: Obviously fake or fraudulent
From IAA SETI Permanent Committee: Rio Scale Calculator with a few changes in wording. Notes:
- SETI / SETA = Search for Extraterrestrial Intelligence / Artifacts
- I propose having non-SETI/SETA ones for whenever SETI/SETA ones would be well-defined, but contacts not part of formal SETI/SETA efforts, like contacts by nonscientists. That would be roughly the 20th century and likely at least the second half of the 19th century. Before that, any contacts would be considered as recorded in archival data (#1).
- Distance #3 evidently refers to the nearest stars to the Sun, out to about 30 light-years / 10 parsecs.
- “Obviously fake or fraudulent” ought to include mistakes, since it is obviously possible to be honestly mistaken.
The motivation for the scale is explained in Almár and Tarter 2000 The Discovery of ETI as a High-Consequence, Low-Probability Event and Almár 2001 How the Rio Scale Should Be Improved. It is applied to several science-fictional scenarios in Shostak and Almár 2002 The Rio Scale Applied to Fictional “SETI Detections”, and the examples there should give an idea of how to use this scale. Further experience with the scale is descrbed in Shuch 2003 SETI Sneak Attack: Lessons Learned from the Pearl Harbor Hoax, where it was used to assess this alleged event as we learned about that event.
Here are some science-fiction scenarios and also some nonfiction ones, taken from the papers “The Rio Scale Applied to Fictional ‘SETI Detections’” (Contact, 2001: A Space Odyssey, Stargate, the Mars Face, and the EQ Pegasi hoax) and “How the Rio Scale Should Be Improved” (the WOW signal), as illustrations of how to use it. I have added to the ones for 2001 and Stargate, and I have also added ones for Mars’s canals, pulsars, and KIC8462852 (“Boyajian’s Star” or “Tabby’s Star”). A signal was recently detected from star HD 164595’s direction, but it seems much like the WOW signal, so I have not added it.
| Event | Type | Mthd | Dist | Rel | Rio |
|---|---|---|---|---|---|
| Contact (movie, Carl Sagan, 1997) | |||||
| Immediately following detection | 3-6 | 5 | 1-4 | 3 | 4-8 |
| After confirmation by other telescopes | 3-6 | 5 | 1-4 | 4 | 6-10 |
| After transponded TV broadcast discovered | 6 | 5 | 3 | 4 | 9 |
| Independence Day (movie, 1996) | |||||
| Immediately following detection | 3-6 | 5 | 1-4 | 3 | 4-8 |
| Moments later, after confirmation | 6 | 5 | 4 | 4 | 10 |
| 2001: A Space Odyssey (movie, 1968) | |||||
| Discovery | 1 | 4 | 4 | 4 | 4 |
| Activation (my scoring) | 5 | 4 | 4 | 4 | 9 |
| Stargate (movie, 1994) | |||||
| Following 1928 discovery | 1 | 4 | 4 | 1 | 2 |
| Seven decades later, when stellar constellations are recognized | 1 | 4 | 4 | 4 | 6 |
| When it is activated (my scoring) | 5 | 4 | 4 | 4 | 9 |
| The Mars Face (1976) | |||||
| Following 1976 discovery in Viking orbiter data | 1 | 4 | 4 | 1 | 2 |
| After 2001 Mars Global Surveyor high-resolution imagery | 1 | 4 | 4 | 0 | 0 |
| EQ Pegasi hoax (1998) | |||||
| After SETI League notification and lack of confirmation by League members | 2-6 | 3 | 2 | 1 | 1-2 |
| After BBC story, and claims of other amateur confirmations | 2-6 | 5 | 2 | 2 | 3-4 |
| Following Australian and U.S. observations and additional Web site anomalies | 2-6 | 3 | 2 | 0 | 0 |
| The WOW signal (1977) | |||||
| Ohio State University observation | 4-5 | 3 | 1-3 | 1 | 1-2 |
| Mars’s Canals (1877, my scoring) | |||||
| Around 1900 (consensus) | 1 | 4 | 4 | 2 | 3 |
| Percival Lowell | 5 | 4 | 4 | 4 | 9 |
| Around 1950 (consensus) | 1 | 4 | 4 | 1 | 2 |
| After Mariner 9 | 1 | 4 | 4 | 0 | 0 |
| Pulsars (1967, my scoring) | |||||
| Discovery | 2-4 | 4 | 1-3 | 1 | 1-2 |
| Identification as Neutron Stars | 2-4 | 4 | 1-3 | 0 | 0 |
| Star KIC8462852 (2015, my scoring) | |||||
| Kepler satellite observations | 1 | 4 | 2 | 1 | 1 |
Here is a comparison of claims of extraterrestrial activity in our Solar System. These claims range from claims in the mainstream scientific literature to claims made by paranormalists, but it is nevertheless worthwhile to compare them. The reliability is rather subjective, so I’ll use the full range of nonzero values.
| Event | Type | Mthd | Dist | Rel | Rio |
|---|---|---|---|---|---|
| Mars’s canals | 1 | 4 | 4 | 1-4 | 2-6 |
| Mars’s moon Phobos’s hollowness | 1 | 4 | 4 | 1-4 | 2-6 |
| The Mars Face | 1 | 4 | 4 | 1-4 | 2-6 |
| The Tunguska explosion | 5 | 1 | 4 | 1-4 | 2-7 |
| Interstellar asteroids | 5 | 2 | 4 | 1-4 | 2-7 |
| Ancient aliens: artifacts, uninterpretable | 1 | 1 | 4 | 1-4 | 1-4 |
| Ancient aliens: artifacts, interpretable | 2 | 1 | 4 | 1-4 | 1-5 |
| Ancient aliens: artifacts, message | 4 | 1 | 4 | 1-4 | 2-6 |
| Ancient aliens: contacts | 6 | 1 | 4 | 1-4 | 2-7 |
| AA archeology: artifacts, uninterpretable | 1 | 4 | 4 | 1-4 | 2-6 |
| AA archeology: artifacts, interpretable | 2 | 4 | 4 | 1-4 | 2-7 |
| AA archeology: artifacts, message | 4 | 4 | 4 | 1-4 | 2-8 |
| UFO observations | 5 | 4 | 4 | 1-4 | 2-9 |
| UFO contacts | 6 | 4 | 4 | 1-4 | 2-9 |
AA = ancient aliens or ancient astronauts. Evidence of them may either be reported on or else discovered archeologically. If reported on, then we would work from documents that contain those reports.
Contacts include both abductions and friendly contacts, and the latter sort would clearly be the most informative — if there is any reason to believe that they are anything more than pure fantasy (reliability 0).
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