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.
I have created
my own version of that quiz,
and also quizzes for version 2.0 of this scale and the London ET-life scale.
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 similar sorts of scales:
- Wikipedia - Beaufort wind force scale
- Wikipedia - Richter magnitude scale
of earthquake energy.
- Wikipedia - Mercalli intensity scale
of earthquake effects.
- Wikipedia - Volcanic explosivity index
- NOAA Space Weather Scales | NOAA / NWS Space Weather Prediction Center:
Geomagnetic storms, solar-radiation storms, and radio blackouts.
- Wikipedia - Torino scale
of asteroid/comet impact threat,
a combination of probability and impact energy.
- Palermo Technical Impact Hazard Scale,
another impact-threat scale.
It is
log10( (probability) / (background probability) ) .
- IAA SETI Permanent Committee: San Marino Scale for evalulating METI
(active SETI) transmissions.
It is
log10( (signal flux) / (quiet solar flux) ) + (character) ,
where the character value is
- 5: Reply to an extraterrestrial signal or message (if they are not yet aware of us)
- 4: Continuous, broadband transmission of a message to ETI
- 3: Special signal targeting a specific star or stars, at a preselected time, in order to draw the attention of ETI astronomers
- 2: Sustained, untargeted message with the intention to reach ETI
- 1: A beacon without any message content (e.g., planetary radar)
- Discovery of extra-terrestrial life: assessment by scales of its importance and associated risks | Philosophical Transactions of the Royal Society of London A: Mathematical, Physical and Engineering Sciences
proposes a "London Scale" in analogy with the Rio Scale.
It is calculated as follows:
(quality) * (reliability)
where
(quality) = (type) + (nature) + (method) + (distance)
Type:
- 5: completely alien life form
- 4: likely to be non-terrestrial, but some uncertainty remains
- 3: life definitely, but a previously unknown variant of terrestrial life (in structure or composition) (e.g. if DNA is present, different amino acids are used)
- 2: terrestrial-type life form, but some uncertainty remains
- 1: possible signature of life, but indirect information only (e.g. volatile, trace)
Nature:
- 6: complex life (high level of organization)
- 5: simple life (low level of organization)
- 4: extant life with suspended functioning (like a spore)
- 3: uncertain whether living or not (like a virus)
- 2: fossilized life or remnants of life forms
- 1: biomarkers (indirect evidence, like volatiles, metabolites, biochemical signatures, etc.)
Method:
- 5: by analysing the result of a sample return mission (origin of the sample is well known)
- 4: by analysing something found on Earth’s surface or in the atmosphere (e.g. meteorite and atmospheric sample)
- 3: by a manned mission, in situ, on another celestial body
- 2: by a surface robot, in situ, on another celestial body
- 1: by remote sensing from the surface of the Earth or from satellites, flybys, etc.
Distance:
- 4: zero distance (on Earth)
- 3: inside the orbit of Jupiter (in situ research more easily possible)
- 2: on or outside the orbit of Jupiter, but in the Solar System (in situ research possible, but difficult)
- 1: beyond the Solar System (in situ research impossible)
Reliability:
- 0.5: certain or highly reliable
- 0.4: probably real
- 0.3: testable, needs further evidence
- 0.2: controversial, but not rejectable
- 0.1: probably not real
- 0: obviously fake or fraudulent
Their examples:
- ALH84001 meteorite: (2+2+4+4) * 0.3 = 3.6.
- The Hungarian dark-dune-spot – Mars-surface-organism hypothesis: (2+5+1+3) * 0.3 = 3.3
- Hoyle–Wickramasinghe hypothesis of panspermia: (2+4+4+4) * (0.1 to 0.2) = 1.4 to 2.8
- Red rain in Kerala, India: (2+3+4+4) * 0.1 = 1.3
Past hypotheses (my evaluation):
- Mars wave of darkening: (2+5+1+3) * 0.2 = 2.2
Listed as "controversial" because of plausible nonbiological hypotheses.
Recent hypotheses (my evaluation):
- Martian methane: (1+1+2+3) * 0.2 = 1.4
Listed as "controversial" because of plausible nonbiological hypotheses.
Possible future detections (my evaluation):
- Exoplanet biota: (1+1+1+1) * 0.5 = 2
Uses the best case of reliability for illustrative purposes,
because all the quality features are worst-case ones.
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.
The table-cell colors correspond to the table-cell values:
black (low value) - blue - cyan - green - yellow - white (high value).
Ranges of values are shown as color gradients.
The colors are made very light so that the numbers may be easy to read.
|
Event
|
Obs Type
|
Method
|
Distance
|
Reliability
|
Rio Value
|
|
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
|
6
|
|
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
|
Obs Type
|
Method
|
Distance
|
Reliability
|
Rio Value
|
|
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).
An updated version of the Rio scale was recently proposed:
Forgan, Wright, Tarter, Korpela, Siemion, Almár, and Piotelat 2018
Rio 2.0: revising the Rio scale for SETI detections | International Journal of Astrobiology | Cambridge Core
It follows the original one in having (quality)x(reliability),
but its quality scale is revised and its reliability scale is much expanded.
All the descriptive text is quotes from the article, but the HTML formatting is mine,
and I have restated the algorithms.
In summary:
- Quality
- What is the estimated distance to the source of the signal?
- What are the prospects for communication with the source of the signal?
- Is the sender aware of humanity/its technology?
- Reliability
- How real and amenable to study is the phenomenon?
- How certain are we that the phenomenon is not instrumental?
- How certain are we that the phenomenon is not natural or anthropogenic?
Here is the calculation of that scale, explained in more detail.
The quality Q is calculated from three parts, with scores Q1, Q2, and Q3:
- Q1: What is the estimated distance to the source of the signal?
- 4: Less than a light day (i.e. in the Solar System)
- 3: Light-days to light-years (i.e. about as close as the nearest star)
- 2: Light-years to tens of light-years
- 1: Hundreds to thousands of light-years (in the Galaxy)
- 0: Longer/unknown
- Q2: What are the prospects for communication with the source of the signal?
- 4: We are in the active two-way communication
- 3: We could respond using the same medium/encoding as the signal
within 20 years
- 2: We can understand the signal or we have artefacts we can study
- 0: No communication is taking place
- Q3: Is the sender aware of humanity/its technology?
- 2: Yes, certainly – the signal is intended for us, specifically
- 1: Possibly, but there is a little or no evidence for this
- 0: Almost certainly not (e.g. they are too far away)
- -1: Senders are apparently extinct
Once these are calculated, one finds Q = max(Q1 + Q2 + Q3, 0).
The reliability comes in three parts, with scores J1, J2, and J3.
The first part, with subscores J1.1, J1.2, and J1.3, is for: How real and amenable to study is the phenomenon?
- J1.1: Is there a significant uncertainty about whether the phenomenon occurred/occurs at all?
For instance, are the data corrupted,
is there a significant risk of misunderstanding or transcription error?
‘Significant’ here means more than 10%.
- 6 (skip the rest): Yes, there is a significant uncertainty
- 7: No, something almost certainly happened
- J1.2: How amenable to study is the phenomenon?
- 0: The phenomena has been observed exactly once (e.g. the Wow! signal).
- 1: The phenomenon has been observed a small but plural number times,
either as multiple targets showing similar phenomena,
or a single target showing multiple similar events.
- 2: The phenomenon has been confirmed to be real and repeated,
for instance by multiple groups using a single instrument to observe the phenomenon
or by an additional observation with a different instrument or from a different site.
- 3: The phenomenon is observed routinely by different groups using different equipment.
- J1.3: Is the discoverer of the phenomenon the same person/group that predicted that such a phenomenon would indicate the presence of alien intelligence?
- -1: The claimants predicted the phenomenon they have ‘discovered’.
- 0: The claimants have identified a new phenomenon, or one predicted by others.
One then finds the total first score J1 = J1.1 + J1.2 + J1.3.
The second part, with subscores J2.1 and 2.2, is for: How certain are we that the phenomenon is not instrumental?
- J2.1: Does the phenomenon look like a known instrumental or psychological effect?
- 0 (skip the rest): Yes. (me: lens flares, subjective pattern-finding, ...)
- 7: No.
- J2.2: What chances do the instrument builders/experts in the method/observers of the phenomenon give that the signal is not instrumental?
- 0: These experts have not weighed in at all.
- 1: These experts give a ∼90% chance that it is instrumental (so a ∼10% it is real).
- 2: These experts give even odds that it is instrumental.
- 3: These experts give <10% chance that it is instrumental.
One then finds the total second score J2 = J2.1 + J2.2.
The third part, with subscores J3.1 and J3.2, is for: How certain are we that the phenomenon is not natural or anthropogenic?
- J3.1: Is there a good reason to think the phenomenon is a hoax?
- 0 (skip the rest, "end quiz"): Yes.
- 1: No.
- J3.2: How does a wide community of experts assess the probability that there are any known sources of natural or anthropogenic signal that could explain the phenomenon?
- 0: A wide range of experts agree that the signal is clearly natural/anthropogenic, or said experts have not been consulted.
- 1: It is consistent with a common phenomenon.
- 3: It is consistent only with a rare or poorly understood phenomena.
- 6: It is not consistent with any known natural or anthropogenic phenomena
(but unknown natural/anthropogenic phenomena could still be the cause).
- 8: Only extraterrestrial, artificial explanations make sense
(i.e. those requiring non-human design and engineering, for instance:
a Dyson sphere, a narrow band carrier wave from an extraterrestrial source, a strictly periodic pulsed laser;
in other words: all natural and anthropogenic explanations been ruled out).
- 9: The phenomenon contains information content of clearly intelligent design
(i.e. it contains a message; or is an obviously artificial and alien artefact available for close – perhaps robotic – inspection).
One then finds the total third score J3 = J3.1 + J3.2.
Once one finds these three scores, one finds the total reliability score R = J1 + J2 + J3 - 20.
Then D = 10(J-10)/2,
and then the final score R = Q*D.
The authors have these interpretations of quality scores Q:
- 10: Revolutionary. Everyday life on the Earth will change forever.
- 8 - 9: The making of an epoch; the future direction of humanity is changed.
- 6 - 7: SETI becomes the ‘study of ETI’. There are good prospects for near-future, limited understanding of ETI.
- 4 - 5: Scientifically revolutionary, but of no everyday consequence.
Prospects for understanding ETIs remain decades in the future.
- 0 - 3: Philosophically ground-breaking, but of limited immediate social or scientific impact.
The prospects for understanding ETIs remain unclear.
They have these interpretations of reliability scores J:
- 10: Aliens. Front page of every major newspaper.
- 9: Significant mainstream press interest warranted, heavy coverage by technical popular press.
Broad agreement that the signal could be due to aliens.
- 7 - 8: SETI interest definitely warranted; technical popular
press interest probably warranted; possible off-beat news item for general press, if expressed with appropriate caveats.
If not aliens, still very interesting.
- 5 - 6: SETI interest probably warranted; technical popular press interest potentially warranted.
- 1 - 4: SETI interest potentially warranted; no press interest warranted.
- < 1: No interest warranted.
They continue to use the values for the overall scale R that are on the top of this page.
Back to my UFO index page