Assessing claims of extraterrestrial life and intelligence

[lpetrich]

That is often done in a very hand-waving sort of way, but I've discovered an attempt to quantify it. To give numerical values for quality of purported evidence (what is being claimed) vs. reliability of that evidence.

It ws inspired by several other scales, the  Beaufort scale of wind speed, the  Richter magnitude scale of earthquake intensity, the  Modified Mercalli intensity scale of earthquake effects, the  Volcanic Explosivity Index of how much was material ejected, NOAA Space Weather Scales | NOAA / NWS Space Weather Prediction Center of geomagnetic storms, solar-radiation storms, and radio blackouts resulting from solar activity, the Torino Impact Hazard Scale of asteroid/comet impact threat, a combination of probability and impact energy, and the  Palermo Technical Impact Hazard Scale which is:

log₁₀( (probability) / (background probability) ).

Coming closer to this subject is the San Marino Scale for evalulating METI (messages to ETI: active SETI) transmissions. It is:

log₁₀( (signal flux) / (quiet solar flux) ) + (character)

where the character 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)

 

[lpetrich]

I have discovered the Rio scale for assessing claims of extraterrestrial intelligence, presented by 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.

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)

The authors have assessed several claims and fictional accounts of contact with ETI, and I have collected their work and expanded on it in The Rio Scale of Extraterrestrial Contacts

They have a Rio Scale Calculator and I have written a version with some additional calculators: The Rio Scale of Extraterrestrial Contacts: Online Quiz Both of them are entirely in-page calculators, and I have written mine with HTML, CSS, and JavaScript.

The type of contact:

• 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

The method of contact:

• 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

The 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:

• 4/6: 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

I must note:

• 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.

 

[lpetrich]

Here are some examples of this score worked out. From Shostak and Almar, 2002, The Rio Scale Applied to Fictional "SETI Detections" on the movie "Contact", about detection of an interstellar broadcast:

• Immediately following detection:
  • Type _ 3 - 6 _ it was a message intended for recipients at interstellar distances.
  • Method _ 5 _ it was detected in a SETI search.
  • Distance _ 1 - 4 _ unknown.
  • Reliability _ 3 _ strong evidence, but it ought to be checked.
  • Score _ 4 - 8
• After confirmation by other telescopes:
  • Type _ 3 - 6
  • Method _ 5
  • Distance _ 1 - 4
  • Reliability _ 4 _ verified by other observers.
  • Score _ 6 - 10
• After transponded TV broadcast discovered:
  • Type _ 6 _ the message was intended for us.
  • Method _ 5
  • Distance _ 3 _ near interstellar distance: the star Vega.
  • Reliability _ 4 _ verified by other observers.
  • Score _ 9

Also from that paper is an assessment of "2001: A Space Odyssey", though I added what happened after the Moon slab was activated:

• Discovery
  • Type _ 1 _ a mysterious artifact discovered on the Moon.
  • Method _ 4 _ as a result of something other than a search for ET artifacts.
  • Distance _4 _ inside the Solar System.
  • Reliability _ 4 _ Certain.
  • Score _ 6
• Activation
  • Type _ 5 _ that artifact demonstrates that it is functional, though it does not try to communicate with us.
  • Method _ 4
  • Distance _4
  • Reliability _ 4
  • Score _ 9

 

[lpetrich]

That paper also discusses the Mars Face, what looks like a large sculpture of a human face:

• Following 1976 discovery in Viking orbiter data
  • Type _ 1 _ what was purportedly an ET artifact.
  • Method _ 4 _ in pictures of Mars's surface taken by that spacecraft.
  • Distance _4 _ inside the Solar System.
  • Reliability _ 1 _ borderline: it could easily have been some naturally-occurring rock formation.
  • Score _ 2
• After 2001 Mars Global Surveyor high-resolution imagery
  • Type _ 1 _ what was purportedly an ET artifact.
  • Method _ 4 _ in pictures of Mars's surface taken by that spacecraft.
  • Distance _4 _ inside the Solar System.
  • Reliability _ 0 _ it was very obviously a rock formation.
  • Score _ 2

I then went on from there and assessed the canals of Mars:

• Around 1900 (consensus)
  • Type _ 1 _ the canals were purportedly ET artifacts.
  • Method _ 4 _ from general observations of Mars.
  • Distance _4 _ inside the Solar System.
  • Reliability _ 2 _ not sure whether the canals existed, or what they were if they existed.
  • Score _ 3
• Percival Lowell
  • Type _ 5 _ the canals were engineering works currently in use, even if not trying to communicate with us.
  • Method _ 4
  • Distance _4
  • Reliability _ 4 _ he was very confident in his conclusions.
  • Score _ 3
• Around 1950 (consensus)
  • Type _ 1
  • Method _ 4
  • Distance _4
  • Reliability _ 1 _ were very skeptical of the canals' existence, with optical illusions often suspected.
  • Score _ 2
• After Mariner 9
  • Type _ 1
  • Method _ 4
  • Distance _4
  • Reliability _ 0 _ the spacecraft's pictures contained exactly zero evidence of nearly every canal's existence.
  • Score _ 2

It is worth noting that Percival Lowell's position was rejected by some of his fellow fellow canal believers. For instance, William Henry Pickering thought that they were some geological effect like big cracks in Mars's surface.

I date the final discrediting to the Mariner 9 mission, because previous spacecraft visits were flybys that did not take pictures of much of the planet's surface, even if there were no canals in those pictures. Mariner 9, however, spent an Earth year in orbit, photographing the entire planet. The canals of Mars: An assessment after Mariner 9 - ScienceDirect

The Lowellian canal network has been compared with the results of Mariner 9 photography of Mars. A small number of canals may correspond to rift valleys, ridge systems, crater chains, and linear surface albedo markings. But the vast bulk of classical canals correspond neither to topographic nor to albedo features, and appear to have no relation to the real Martian surface.

 

[lpetrich]

A similar scale has been proposed for extraterrestrial life, including extraterrestrial microbes, the "London scale": 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

Here also, one calculates a score as (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

The reliability scale is the same as in the Rio scale.

I considered what one could expect to see across interstellar space. All four quality factors are 1, making a total of 4. Type and nature: from atmopheric gases produced by the organism. Method: remote sensing. Distance: outside the Solar System. The best case for reliability is 5/10, giving a score of 2.

So to do better, one must search in the Solar System, and there are places to look, like Mars, Jupiter's moon Europa, and Saturn's moon Enceladus.

 

[steve_bank]

Th probability of life in any from elsewhere is subjective. For all we know we Erath is a one time event .

The probability of tossing a die is 1 in 6 because the outcomes are enumerated. There is no way to enumerate outcomes elsewhere in the universe .

 

[lpetrich]

Th probability of life in any from elsewhere is subjective. For all we know we Erath is a one time event .

That's not what I was describing. I was considering how to assess *claims* of such entities.

 

[lpetrich]

I'll now assess Martian methane.

• Type: CH4 is indirect evidence: 1
• Nature: CH4 is a biomarker: 1
• Method: detected by some orbits and the Curiosity rover: 2
• Distance: Mars is not the Earth, but inside Jupiter's orbit: 3
• Quality: 7
• Reliability: hard to rule out odd geological effects: 2
• Score: 1.4 with best case 3.5

If fossils were discovered on Mars, then that would be a big step forward.

• Type: separate origin very likely: 5
• Nature: fossils 1
• Method: discovered by a rover: 2
• Distance: Mars is not the Earth, but inside Jupiter's orbit: 3
• Quality: 12
• Reliability: if it's hard to tell that it's a fossil: 2
• Score: 2.4 with best case 6.0

Bringing a putative fossil to an Earth laboratory would bump the method up to 5, the quality up to 15, and the score up to 3.0 - 7.5.

 

[lpetrich]

A possible bit of evidence in fossils brought back to Earth is biomarkers. Extraterrestrial organisms would likely have membrane lipids, but there is no reason to suppose that they would be identical to Earth organisms' ones. Earth life has a curious variation between the three domains of cellular life: Bacteria and Eukarya have fatty acids, while Archaea has terpenes.
Reappraisal of hydrocarbon biomarkers in Archean rocks | PNAS

The advent of oxygenic photosynthesis set the stage for the evolution of complex life on an oxygenated planet, but it is unknown when this transformative biochemistry emerged. The existing hydrocarbon biomarker record requires that oxygenic photosynthesis and eukaryotes emerged more than 300 million years before the Great Oxidation Event [∼2.4 billion years ago (Ga)]. We report that hopane and sterane concentrations measured in new ultraclean Archean drill cores from Australia are comparable to blank concentrations, yet their concentrations in the exteriors of conventionally collected cores of stratigraphic equivalence exceed blank concentrations by more than an order of magnitude due to surficial contamination. Consequently, previous hydrocarbon biomarker reports no longer provide valid evidence for the advent of oxygenic photosynthesis and eukaryotes by ∼2.7 Ga.

Hopane is a polycyclic hydrocarbon derived from hopanoids, which are made by cyanobacteria and sterane a polycyclic hydrocarbon derived from steroids, which are made by eukaryotes. Both of them are made from squalene, a triterpene, a polymer with 6 isoprene units.

One might expect terpenes or fatty acids in extraterrestrial organisms, but steroids and hopanoids are a bit too specific.