Why Are UAPs Associated With Naval Aviation?

We're more likely to find artifacts from technology-using aliens - self-reproducing (von Neumann) probes - rather than the aliens themselves, or even to recognize and understand their signals against background, if any. Indeed, humans may be just at the technological threshold of building such probes right now, but we're far from any serious discussion of manned interstellar travel, and in fact it may never be biologically feasible. Such objects are likely to be found associated with lower gravity objects, ie the asteroid belt, where they can obtain materials and build more of themselves. The further they are from home, the less likely they are to adhere to some "mission", and the more likely they are to have mutated and been selected merely for fecundity (reproductive ability.) Therefore it's not obvious that they would be particularly interested in finding other examples of intelligence. They could very well be much more interested in finding other von Neumann probes, and humans might therefore not be the most interesting thing in the solar system to them. If this is the situation that obtains, this resolves a contradiction: other technology-using species have indeed appeared before us, but there's little evidence of them here.

If the von Neumann probes are built from metal, and one planet over the last few centuries suddenly has large metal objects moving around its surface (ships) and smaller metal objects moving much faster through the atmosphere - then THOSE might be interesting. You might expect the probes to be especially interested in locations with lots of ship and air traffic, and especially the ones with the fastest air-objects, especially if the fast air-objects come and go from the large metal objects on the surface. It's been observed separately by other writers that, from the standpoint of an off-world but in-solar-system alien observer of Earth's behavior in terms of natural processes, the appearance of metal objects in the atmosphere and then suddenly in orbit is the most interesting phenomenon that has appeared here for many millions of years at least.

The fact that it's US Navy aviators who have reported many of the UAP sightings is obviously relevant. Given that the reported observations are made by multiple modalities (naked eye, radar, thermal) and official US agency reports describe as likely mostly physical objects, it's unlikely these are glitches: that is to say, either they're real, or they're made up, possible as sort of intelligence or misinformation operation that we civilians are caught in. But if it's real, two questions are important to the hypothesis.

First: is there really a higher rate of UAP sightings around US Navy aviation areas (as there seems to be so far, with sightings concentrated around San Diego and Virginia Beach) or is this just bias because there are more instruments and observers there? Such is the frequency of these events according to the reports that a relatively low-budget operation with some weather balloons over a low-traffic area could move the needle on whether naval air stations are "enriched" for these objects. (If it does not make any such observations, it would suggest either it's a misinformation campaign, or they're real but concentrated around naval air stations.) Related: do JFK or LAX have similar sightings? Or Heathrow? Narita?

Second: is it really an American (or mostly American) problem? Is the pattern repeated around the world at other countries' naval air stations? China or Russia might not be interested in sharing this kind of information, but NATO allies might be. That said, if an unfriendly country discloses it is seeing the same thing, and it has no explanation, then it's much more likely that these objects are real, and at least are not human-created phenomena.

Review of Three Body Problem

Warning: spoilers.

The Good

Western readers will inevitably learn a lot about the Cultural Revolution period and the attitudes about it people are comfortable expressing in print today. During this interview and in his postscript to the American edition, Liu distances himself from any reading of his work as cultural critique, maybe a bit too strenuously. Whether he should be credited as pointing us to a Straussian reading or this is just pragmatic avoidance of political attention is not clear to me.

Related to this, Western readers in particular are keen to find parallels between Trisolaris and Earth to China and America. Again Liu himself states this isn't what he's doing, and in any event it's not clear which planet would stand for which country. Trisolaris goes through cycles of death and rebirth not unlike China's dynasties (in fact, in the in-novel video game, represented literally as China's dynasties) and Ye is even explicitly described at one point as emerging from the chaotic winter of the Cultural Revolution. The regimented, autocratic aliens of Trisolaris are coming to dominate the naive Earth - the easy-going, beautiful Earth that fluorished in ignorance, as a Chinese author might imagine America. But this doesn't really fit. For one thing, Liu certainly doesn't come across as having any romantic fantasies about America; and Trisolaran sabotage of Earth's rapid advance also smacks of Chinese resentment at perceived Western interference in its rise. If two opposing narratives can fit so well, then I think we're probably crowbarring them into a story where they don't belong. Then again, a symbolic scheme need not be entirely consistent. Case in point, in District 9, are the aliens Soweto residents, or clueless interlopers like the Afrikaaners? Likely both, at various points.

The single best feature of this novel is its explosion of this idea that any technologically advanced civilization must necessarily be a moral one; that humans are inherently and uniquely bad; and that therefore, contact with starfaring aliens can only improve our lot. (This idea of humans being uniquely evil is actually grossly anthropocentric, morally pre-Copernican, invariably casting the rest of humanity as evil, except of course for the enlightened individuals lecturing the rest of us. It smacks of teenagers claiming to be Satanists. Why not just reject Christian symbolism entirely? Because that doesn't make your parents as mad.) Things did not work out well for the natives of the New World, and that was contact between the same species. And Cortez and Pizarro were surely more technologically advanced than the Aztecs and Incas, so why were they not also morally superior? Hence the moment when the police officer almost can't wait to show Ye the content of the messages they found on the Adventists' secret ship and destroy her "beautiful fantasies." It's worth pointing out that almost every cosmologist or astronomer who has a position regarding sending messages to other stars says that if the space-phone rings, we should not answer. And yet in the real world, many such attempts to advertise our presence have already been made, on at least one occasion frivolously as an art project.

The constant frustrated attempts to understand Trisolaran seasons raises a genuinely frightening implication of the problem of induction as it relates to life on Earth. Once the Age of Enlightenment arrived, the idea that we did not understand our world (or could not understand it) in some very relevant way became terrifying. Early strange fiction like Hodgson began to explore this horror of the irrational, of a universe which at its base could not be understood. Philosophically speaking, there are two categories of incomprehensible universes:

• Type 1: We don't understand the universe merely because we have not had the chance to observe a full cycle or the full domain, but ultimately, the universe is still lawful. Asimov's Nightfall is an example.
• Type 2: We don't understand the universe because we cannot. The universe is fundamentally irrational, or at least unknowable to narrow human intellects. Lovecraft's Cthulhu novels are an example; also, frequently, Dying Earth stories.

In both cases, encountering the fundamentally irrational can bring about the collapse of civilization, insanity upon directly observing the unknowable, and sometimes even the dissolution of physical reality. However, the problem of induction and horror of the irrational were not ultimately examined here - on this count the novel ended up being disappointingly mundane for reasons detailed below. Still, in the real world, at the very least Type 1 encounters with the irrational asteroid impacts, Carrington events, and gamma ray bursts are scary enough - at this writing, there is an Oort Cloud object possibly hundreds of kilometers across moving toward the orbit of Saturn that had until now escaped notice.

Ye is the tragic character, obviously, and she is the best-drawn. This woman suffers so much trauma, but the worst is that she realizes possibly the worst thing that anyone has ever done in history is her own action - she sacrificed her husband and accepted the loss of her daughter, then found that what she thought was the one meaningful achievement of her life, turned out to likely to mean the end of the entire human race at the hands of equally immoral beings.

The frustrations introduced by the sophon particle is reminiscent of the Sisyphean problems plaguing CERN and keeping it from finding the Higgs boson (which we know eventually was found.) But it's worth pointing out that in 2009 there was an apparently serious proposal that time travelers (or the Higgs boson itself) were interfering from the future with CERN to prevent some catastrophe that the Higgs boson, if created, would foment. Alas, we still exist.

I usually enjoy unexpected pacing and structure if I'm being surprised rather than bored or confused, and in this case, I was more often surprised. For one thing, this is a two-protagonist novel (Ye and Wang.)


The Bad

You will note the novel shares a number of the following weaknesses with the genre in general. First is characterization. Outside Ye and to some extent Shi, we barely know who these people are. In Wang's case, we only find out he has a family when he goes home, then he doesn't think about them again, even as he travels around the world, or in the face of mortal danger to himself, or even a threat to the entire human race. He finds out that we're dealing with aliens, and he barely reacts at all. Even a Dan Brown protagonist at least wanders around a novel imbuing the revelations with a sense of wonder and profundity. Wang isn't even a mouthpiece for ideas.

Liu offers very few sensory descriptions of anything, except the village outside Red Coast. Ye's experiences there are described in conspicuous sensory terms that stand out. It should not be a surprise then that Liu grew up in a poor rural village.

For any reader familiar with near-Earth stars, it wasn't a surprise that Trisolaris turned out to be Alpha Centauri.

If we're applying hard science fiction rules, then it's too great a coincidence that the aliens are within a few millennia of our own technological level. Aliens are much more likely to be either trilobites, or "phyla beyond [human] knowing" to use Benford's term, than something at all cognitively similar to humans that comes here on metal ships. This is a point that many readers of science fiction will not mind, but will bother anyone familiar with current academic thinking regarding the Fermi paradox. The fact that they even feel the need to insult us - "YOU ARE BUGS" projected on our retinas - makes them seem a bit too human-like. In fact the entire description of the "real" internal behavior of the Trisolarans is far too anthropomoprhic. There was some mention of the "living computer" having been a real thing there, and their movements being much faster than humans', so I hope I'm missing some sleight of hand like the one Vinge used in Deepness in the Sky (the spider-aliens were in fact much more alien than they were portrayed earlier.)

Plot problem - if the goal is to disable scientists, then the sophons could do a lot better than create a spooky countdown in someone's visual field. You could blind them, or cause them to hallucinate. In the real world, hallucinations and even tinnitus alone can effectively disable people. Sensory disruption is much more effective than some higher order cognitive interference introduced by undermining ideas in a lawful universe. Furthermore this suggests a shockingly detailed knowledge of human psychology on the Trisolarans' part.

In the end I did not find that there were really new ideas developed in the novel; what looked like it would be an interesting exploration of the problem of induction or the rational nature of reality (see above) turned out to be industrial sabotage done by aliens instead of human enemies. The use of entangled programmed fundamental particles is interesting but so far beyond anything we think might be real that it's effectively fantasy. China Mieville has advanced the idea that the authorial voice of science fiction is one of radical authority - effectively, "here is how reality itself works. Accept it as possible in order to continue reading." (You might argue that limiting the ideas to known physics either elevates hard sf to the "correct" genre, and/or that it can only produce fictional worlds of straight line extrapolation that people in the future will regard as the early twenty-first century's answer to steampunk. But science and actual speculations thereon rather than just word play is what we know is real, and sticking to the rules of the real world is what keeps a story from being fantasy. This is why Star Wars is a a fantasy movie, masquerading as science fiction by giving its wizards and barbarians spaceships.)

A wild idea couched in the language of science even if the work is really fantasy, or even comedy (see: infinite improbability drives) can still be a good vehicle for thought, but unless you're showing us how to actually in real life unfold and program a proton, you don't need to devote so much space to it. This isn't a screed against exposition, which I think is unfairly devalued in science fiction. If you're introducing a new idea, you either have to stop and unpack it, either in the characters' voices, or through direct description. But the sophon programming section is unnecessarily long and actually became quite boring, the science fiction version of John Galt's sixty page monologue, and had nothing to do with actual science. Maybe this is a tendency of modern Asian fiction - Murakami's Hard Boiled Wonderland has a curiously long-winded description of skull-tapping and at the time I gave the author credit for doing something that I just wasn't getting, but I'm much less sure this is the case in a less literary novel.

I have a personal distaste for fantasy worlds inside science fiction novels. Spacetime folds that take characters back to their childhoods, neural interfaces that make their subconscious a real place, or in this case, a VR video game. It removes constraints from what the writer wants to do and becomes literary expressionism, which in novels (particularly those low on sensory description) seems watery and uncompelling.


In the end, after the hype, I was a bit disappointed. I'm glad I read it but the novel's strengths were really its different setting on Earth and historical perspective of the author. If this were an American science fiction novel it would be clearly mediocre.

Prediction: Venusian Phosphine is a Metabolic Product of Living Cells Already Detected As Unknown Absorbers

(Added later: since I wrote this, further research has provided evidence showing it is very unlikely that the unknown absorbers are biological. Not only was the phosphine paper a product of bad spectrometry that failed multiple attempts at replication, there are at least two papers - Jiang et al 2024, and Egan et al 2025 - that have provided good candidate abiotic explanations for what the absorbers could be.)

The last two years have provided us with the strongest evidence ever assembled of extraterrestrial life:

1. Prior theories about relic ecosystems surviving in the more Earth-like parts of Venus's atmosphere.
2. Detection of UV absorbers the size of bacteria in Venus's atmosphere, with no explanation as to their identity.
3. Prior, independent advancement of phosphine as a biosignature gas.
4. Detection of phosphine in the Venusian cloud decks with no explanation for its persistence.

Here I propose that Venus had an iron-sulfur ecosystem with a chlorophyll-equivalent that absorbs closer to the UV spectrum rather than visible light - essentially, "UV-synthetic" Venusian cyanobacteria. The oceans boiled away and Venus became hotter and more acidic from volcanism and possibly, their own Great Sulfuration (or Sulfur Oxidation, equivalent to Earth's Great Oxygenation.) The only survivors were the UV-synthetic Venusian archaebacteria that now live in the upper atmosphere. Today these have a life cycle like that described by Seager et al (2020), powered by UV and producing phosphine - Unknown Absorber Phosphine Producers (UAPPs.) They are likely related at great time depths to life on Earth. Initial research question is to see if areas of unknown absorbers correlates with phosphine, which can be done from Earth. Probes that collect material in the upper atmosphere could fairly straightforwardly check for aspects of biochemistry using an onboard instrument, and a sample return mission could be extremely productive.


Phosphine Production in the Clouds of Venus

If you're reading this you likely know that phosphine (PH3) was detected in the atmosphere of Venus - Vox explainer here; original paper by Greaves et al here. The measured concentrations are at biology-consistent levels, at an elevation where the pressure and temperature are similar to Earth's. This is by far the strongest evidence of extraterrestrial life yet discovered, with evidence from multiple sources.

Phosphine has been advanced as a possible seed compound delivered to Earth on comets or asteroids early in its history. But the chemistry of its formation in space (or on gas giants) is not mysterious. It's in the Venusian atmosphere where so far we can't explain its presence without some process that continuously replenishes it. One criticism of speculation about possible Venusian biochemistry is that just because we don't know how to make phosphine under Venusian conditions, doesn't mean we're looking at alien biology. True; but among these criticisms have not been any suggestions so far about what it might be. (Either way, we're about to learn something.) It's suggestive that this data is not completely unexpected - it can be fitted to prior hypotheses. We've been speculating more and more concretely for decades about how life might survive in the atmosphere of Venus for decades (see Morowitz and Sagan 1967.) A fairly elaborated model of microbial life in the atmosphere of Venus was advanced recently by Seager et al, consistent with observations so far. This should also increase our confidence in the Venusian-cloud-life hypothesis, that even before phosphine was detected, Sousa-Silva et al suggested phosphine as a biosignature molecule, independent of finding it on Venus.


A Related Mystery? The Unknown Absorbers



In visible light and false-color UV absorption. It's unusual to have such contrast in absorption at different wavelengths. Image credit syfy.com

For decades we have known that there are partciles about 10^-6 meters (the size of bacteria) in the Venusian atmosphere at a similar altitude (at 47 to 64km) as the phosphine detection above (at 57km and above). The dark bands we can see with the naked eye in the Venusian atmosphere contain more of them, but as you can see above in the UV image, they are much higher contrast (more absorbant). As with the origin of Venusian phosphine, the identity of the absorbers remains controversial, and Venusian biology had been advanced previously as a candidate explanation (Limaye et al 2018). The phosophine paper points out that there is more phosphine at mid-latitudes than the equator or poles, which by naked-eye examination of images of Venus, seems also to be where the absorbers are. It seems a relatively straightforward study to correlate the two, but as the absorbers move on a scale from minutes to days, data would have to be collected simultaneously. The stronger the correlation (especially within the same latitude) the more our confidence in the UAPP hypothesis of Venus cloud life would be increased.


What About Bacterial Life in Earth's Cloud Decks?

Earth's clouds do indeed contain lots of bacteria, and not just incidentally - some of them clearly evolved to take advantage of the precipitation cycle and indeed to deliberately cause ice to enucleate around it, like Pseudomonas syringae (this is actually economically relevant as the water ice-enucleation proteins produced by this species is used in the water fed into snow guns at ski resorts.) Bacteria have been found all the way up to 28 miles above the surface, where the pressure and temperature are both much lower and considerably less hospitable even to Earth's own life than the cloud decks on Venus. While we can't say there is an actual bacterial ecosystem in Earth's clouds (one which persists without interacting with the surface), we haven't really looked for one either; most of our interest in these organisms thusfar comes from studying plant pathogens that spread through weather events. It's worth pointing out that there is phosphine in Earth's upper atmosphere as well, with no clear mechanism for how it forms there. It should be noted that there is less in Earth's upper atmosphere by about 3 orders of magnitude; the levels in Venus's atmosphere are more similar to that found immediately around actively metabolizing bacteria on Earth's surface.


Toward an Evolutionary History of Venus

Why would life exist on the most hellish world in the solar system? The answer is that for at least 75% of its lifespan, Venus was a much more Earth-like planet with cooler temperatures and oceans.

There are two possible, not mutually exclusive stories that explain how this planet came to be the Venus we know today.

The first is that Venus was a little too close to the Sun, which caused its oceans to evaporate, plate tectonics to cease, and subsequent cataclysmic volcanism. As the oceans evaporated, the water vapor trapped the heat and accelerated the process. The deuterium/hydrogen ratio on Venus is about 150 times higher than Earth, where comets have at most a 3 times higher ratio than Earth, suggesting a very gradual loss to space of hydrogen from water and preferential retention of the heavier nucleus. Water lubricates plate tectonics, per Solomatov 2001. Climate modeling suggests that Venus may have had a habitable climate with liquid water at the surface until 715 MA ago (Way et al 2016.) The subsequenct evaporation of the oceans resulted in a planet where plate tectonics ground to a halt, and with no crustal mechanism to dissipate heat, and finally between 700 and 500 MA ago, Venus erupted in planet-wide massive flows that resurfaced the planet, utterly dwarfing any similar events on Earth (like the Siberian Traps.) This released the massive amounts of sulfur that we see today. This is the received wisdom and could entirely explain the modern state of Venus, and may alone be enough to explain all the sulfur.

There is another version of the story which reverses the causality - eruption causing evaporation, advanced by Way and Del Genio in 2019. It's worth noting that Venus has a thicker crust than Earth, owing to its lack of a large moon; therefore we should expect that the flows, when they do finally cause the crust to fail, are much stronger than in the parallel situation on an evaporated Earth.

The second possibility is obviously more speculative, a parallel to the Great Oxygenation in the history of life on Earth. In Earth's history, anaerobic cyanobacteria produced so much oxygen that they effectively poisoned themselves, but also set the stage for aerobic life. This could have been a great coincidence - there may just have happened to be genes close enough in design space to assemble oxyidation defenses and an aerobic metabolic pathway, and without such a coincidence, that may have been the end of life on Earth, or it may have settled into a simple bloom-and-bust oscillation as our bacterial mats may have for hundreds of millions of years evidenced by banded iron formations found in ancient rocks where they persist at the surface. (See discussion of endogenous extinctions here, which this section partly recapitulates.)

While an interesting idea, by Occam's razor we should spend no further time considering a possible Great Sulfuration, as we can explain the death of the Venusian surface ecosystem entirely based on abiotic meteorological and geological processes as above. It's also the case that the presence of increased CO2 relative to Earth can be easily explained by abiotic processes as well. Using ingenious reasoning about the necessary atmospheric pressure for flying dinosaurs' wings to function as well as the known rates of deposition of CO2 as carbon in continents and the ocean, we can arrive a figure of the equivalent of 85-100 bars' worth of CO2 trapped in the Earth's crust, similar to what is currently in the Venusian atmosphere. Presumably the atmospheric pressure of Venus was lower during its oceanic period owing to the same process, and rose subsequent to the evaporation, but I am not aware of any modeling retrodicting from oceanic evaporation 500-700 MA ago to the current pressure and mass of CO2 on Venus.

All this is to say that life on Venus may have gone a different way, but started quite similarly. We're now fairly confident the first metabolism on Earth was sea vent iron sulfur organisms, using sulfur in what is now oxygen's chemical role. The Great Oxygenation may have only happened when it did, a full 1.5 billion years after the first life and at least 800 million years after photosynthesis appeared, because an asteroid delivered molybdenum, allowing nitrogen fixation and more efficient anaerobic metabolism. Whatever the reason, had this happened prior to photosynthesis, we may have ended up with an Earth poisoned with sulfur or at least with a massive amount of oxidized sulfur.


Two Obvious Problems for the "UAPP Cells" Hypothesis for Life on Venus

There are two major hurdles to overcome in any argument that there is life in the cloudtops of Venus. The first is the question of how life operates without water, or with very little water; this would actually be a more stunning find than merely life which can tolerate high acidity! The second is the failure thusfar to detect any organics in the atmosphere. Without water and organic molecules, it's very hard to see how this won't end up being an interesting abiotic route to phosphine production along with some crystal we weren't anticipating at that altitude. That said, organic compounds on Venus may not be as unlikely as one might think - there was a Venusian equivalent of the Miller-Urey experiment performed, where under conditions of the Venusian atmosphere, organic compounds including amino acids were produced.

Furthermore, there remain arguments for an abiotic explanation for the unknown absorbers, specifically ferric chloride (Petrova 2018). Interestingly, this is partly advanced to explain another mystery which is the presence of rainbows ("Venus glory"), first observed in 2014 in the Venusian atmosphere.


Implications for Evolution in General and the Future of Life of Earth

It is more likely than not that life on Venus will be distantly related to life on Earth. A massive amount of material has been transferred between bodies in the solar system, with actual numbers calculated here; at that same link you will see reference to the survival of uncontrolled re-entry during the Columbia crash by not just bacteria, but animals (C. elegans worms, found alive on the ground weeks after the crash.) This is actually the more boring possibility, because we would learn much more about the basic principles of evolution and the possibilities of biochemistry beyond Earth's provincial commitments, if we really had a novel origin. Either way, if there is life on Venus, the likelihood of life on Mars, Europa, Enceladus and even Titan jumps dramatically, even if it's "just" a long-lost relative. I expect that ultimately the impact of finding life on Venus will be some neat new biochemistry (the old extremophiles will seem quaint) and a bit more information about how evolution can proceed.

It is unclear how we should feel about Venusian cloud UV-cyanobacteria in terms of the Great Filter, which suggests that the more life we find in the universe and the closer in terms of evolutionary stage to humans, the more concerned we should be - because the more likely our own extinction is before we can colonize planets beyond our own. If further exploration of Venus yields trilobites or vertebrates and these cells are all that are left, we should worry much more. In contrast, if Venus never got past vast floating bacterial mats (either in its clouds or ancient oceans). that's a bit more comfortable for us.


REFERENCES

Bains W, Petkowski J, Sousa-Silva C, Seager S. Trivalent phosphorus and phosphines as components of biochemistry in anoxic environments. Astrobiology 19, 7 (July 2019): p. 885-902 doi 10.1089/AST.2018.1958

Glindemann D, Edward M, Kuschk P. Phosphine gas in the upper troposphere. Atmospheric Environment Volume 37, Issue 18, June 2003, Pages 2429-2433

Greaves JS, Richards AMS, Bains W, Rimmer PB, Sagawa H, Clements DL, Seager S, Petkowski JJ, Sousa-Silva C, Ranjan S, Drabek-Maunder E, Fraser HJ, Cartwright A, Mueller-Wodarg I, Zhan Z, Friberg P, Coulson I, Lee E, Hoge J. Phosphine gas in the cloud decks of Venus. Published: 14 September 2020. Nature Astronomy (2020)

Levenspiel O, Fitzgerald TJ, Pettit D. Was the Atmospheric Pressure Different at the Time of Dinosaurs? Chemical Innovation, December 2000 Vol 30, No.12, 50 – 55

Limaye SS, Mogul R, Smith DJ, Ansari AH, Słowik GP, Vaishampayan P. Venus' Spectral Signatures and the Potential for Life in the Clouds. Astrobiology. 2018 Sep 1; 18(9): 1181–1198. Published online 2018 Sep 12. doi: 10.1089/ast.2017.1783

Morowitz H & Sagan C. Life in the Clouds of Venus? Nature volume 215, pages1259–1260(1967). 16 September 1967.

Otroshchenko V.A., Surkov Y.A. (1974) The Possibility of Organic Molecule Formation in the Venus Atmosphere. In: Oró J., Miller S.L., Ponnamperuma C., Young R.S. (eds) Cosmochemical Evolution and the Origins of Life. Springer, Dordrecht. https://doi.org/10.1007/978-94-010-2239-2_40

Petrova EV. Glory on Venus and selection among the unknown UV absorbers. Icarus Volume 306, 15 May 2018, Pages 163-170

Seager S, Petkowski JJ, Gao P, Bains W, Bryan NC, Ranjan S, Greaves J. The Venusian Lower Atmosphere Haze as a Depot for Desiccated Microbial Life: A Proposed Life Cycle for Persistence of the Venusian Aerial Biosphere. Astrobiology. Published Online:13 Aug 2020. https://doi.org/10.1089/ast.2020.2244

Sousa-Silva C, Seager S, Ranjan S, Petkowski JJ, Zhan Z, Hu R, Bains W. Phosphine as a Biosignature Gas in Exoplanet Atmospheres. AstrobiologyVol. 20, No. 2. Published Online:31 Jan 2020 https://doi.org/10.1089/ast.2018.1954

Way MJ, Del Genio AD, Kiang NY, Sohl LE, Grinspoon DH, Aleinov I, Kelley M, Clune T. Was Venus the First Habitable World of our Solar System? Geophysical Research Letters. First published: 11 August 2016 https://doi.org/10.1002/2016GL069790

All Attempts to Broadcast Our Presence to Nearby Stars Should Be Forbidden

Here you can find a list of when there might be a response to known prior contact attempts within a century, assuming immediate light-speed response, and whether there are known terrestrial planets around the stars. This is incredibly dangerous and reveals the presence of intelligence on Earth to anything that might be listening, and should be immediately stopped (see Stephen Hawking's take on this here.) Granted, astronomers' definition of habitable - "terrestrial planet orbiting in liquid water temperature zone" - leaves a lot to be desired.

Until now. Measurements of terrestrial planets can now show if there is an atmosphere and it contains hydrogen, oxygen, and N2, making at least some water quite likely (Konatham et al 2020.)

We can update the list of stars where we've already broadcast contact attempts, with these new stricter criteria. There are two planets with atmospheres and likely water that we have deliberately broadcast to: Teegarden's Star, a red dwarf (with two planets with likely water), with a response possible by 2036; and GJ273b (Luyten's Star), with a super Earth with likely water, responding at earliest 2043.

Two facts to modify our enthusiasm:

• Both are red dwarfs, which have a habit of flaring. However, Luyten's Star is quiet by these standards.
• Also, aliens looking at our solar system using the same definition would keep both Mars and Venus on this stricter habitable list. Both do have atmospheres and some water.

Proxima Centauri is the closest star but in this more-strict list of habitable planets, but we haven't deliberately targeted it. It's worth pointing out that even if there were a twin Earth there, we still wouldn't be able to hear them (the C-index - a rule of thumb, assuming that strength of a civilization's emissions and ability to detect increase in concert.)

(Encouraging to amateurs: Teegarden's Star was discovered by a group of non-professional astronomers poring over data online, without access to telescopes.)

Konatham S, Martin-Torres J, Zorzano M. Atmospheric composition of exoplanets based on the thermal escape of gases and implications for habitability. Published:09 September 2020https://doi.org/10.1098/rspa.2020.0148

New Approaches on What the Fermi Paradox Means for the Future of Humanity

I was lucky to attend a video lecture by James Miller, economist at Smith College, facilitated by Joshua Fox. Thanks for having this event! I contacted James to let him know I would be posting this and to let him proofread my recapitulation of his argument so as to avoid mis-paraphrasing him; my thanks to him for taking the time to correct me on several points. Of course any errors are mine.

Much of this is familiar terrain for those of us who spend our time considering X-risk and the Fermi paradox. Miller's thesis is that we are at a critically important point in human history, a window where we think that in the near future we can start colonizing the galaxy (the year 2614 at earliest, by this calculation) but at the same time where we are smart enough to destroy ourselves. Since it is not obvious that the galaxy has already been colonized by other civilizations, there may be a Great Filter stopping this from happening. Miller uses the analogy of a person about to climb a mountain, believing that everyone else who has attempted it has died in the process.

Several challenges were discussed by attendees. (If you attended the lecture and want to claim credit for your question, please comment below, thanks.)

1. It's too early to say there are no civilizations; it may not be so easy to detect them or rule them out. We're still discovering metazoans in Manhattan so it seems a little early to rule out von Neumann probes on low gravity bodies in the solar system. We've barely begun to catalog the fauna of our own ocean floors. We could not detect a twin Earth emitting the same radio energy (the C-index), even if it was orbiting Alpha Centauri. Miller points out that even if there were only a few civilizations in the Milky Way preceding us, "the galaxy is older than it is big", and these earlier civilizations could have colonized it already.
   
   
2. He made the point that the things which prove advantageous in the midst of evolving on a single planet might have no such advantages in terms of galactic colonization. Very true; I would argue that we are much more likely to find alien artifacts, than the aliens themselves, as all of us meat-creatures might be stuck on our planets while our machines colonize the galaxy. To that end, (my point) it's entirely plausible that the Solar System could be littered with space probes and we haven't found any yet, or did, and just didn't know what we were looking at.
   
   
3. I would therefore extend Miller's analogy like this. Only in the process of climbing the mountain, does our climber develop wilderness skills and begin to see things that resemble his own boot tracks, etc. and finally as he approaches the summit realizes that lots of people have climbed it, come down the other side, and their descendants have built large villages which due to his previous ignorance he has not been able to locate. (Or, maybe just some of their livestock, trained birds-of-prey, etc. have made it.)
   
   
4. Active attempts to bring ourselves to the attention of aliens have occurred (METI) and been roundly criticized. Miller notes that the risk of extinction from aliens over the next few centuries is lower than eg bio-terrorism or an intelligence singularity. True; but we still may be making life more difficult for our descendants. Related to this, he proposes an ingenious experiment that for a month we should shout our heads off electromagnetically, and see if there is any strange activity. While I agree it's unlikely we'll get invaded next week, I still think the risk:benefit does not work out and there are just too many unknowns, and we may be screwing our distant descendants. Miller suggested that enforcing a moratorium on METI-like activities is probably impossible.
   
   
5. He argues that technological singularities of the paperclip maximizer variety are unlikely to be a major contributor to the Great Filter, because we would be able to see the boundary of it as it expanded (unless it was doing so at light speed.) My concern with this is that, while an AGI might be much smarter than its creators, it is still not omniscient, and the impact of its actions could in principle still outstrip its ability to predict that impact. This is the story behind the rise of human intelligence and the sixth great extinction that we're living through, but has happened in pulses of endogenous extinctions throughout Earth's history (the rise of superpredators every fifty million years or so, the Oxygen Catastrophe). The lesson of evolution here on Earth is that the smarter things are, the faster their behavioral plasticity "catches up with them" in exactly these sorts of disasters, so to suppose that alien paperclip maximizers are immune to this problem is to argue that a qualitative change in ecological dynamics has occurred.
   
   
6. There were two (possibly unappreciated) related questions asked: one about civilization perhaps being bad for sustaining civilization (witness declining birth rates in the developed world) and another that intelligences might prefer virtual reality - involution - to expanding into space. Miller points out the passive version of the "baseball bat" problem: you can live in heaven, but if a bad guy comes and bashes your server with a club and you as you sleep in your VR pod, that's the end of it. (Related: dynamic complex systems like minds, in principle, tend to drift toward delusion and suffer inherent cyclic crises.) It's a thesis for someone in psychology or a related field to note whether there is causation or just correlation between the increasingly encompassing virtual reality-like entertainments available in the developing world, and declining birth rates.
   
   
7. One questioner asked about the distinction between intelligence and civilization - humans have had a "civilization" only since agriculture. This was a really original line of thought. Therefore, there could be many alien intelligences, but few or no civilizations. One solution for humans avoiding the Great Filter would be to abandon civilization and go back to hunting-gathering - not directly suggested, but this is the only implication of such an argument I could think of. The extreme number of assumptions built in to discussion of alien civilizations should always be pointed out - civilization is something that collections of human nervous systems do, and it is not clear it is a necessary consequence of intelligence. (As a physician I ask: do we assume the aliens will have similar EKG waveforms and liver enzymes as us? No, because that's ridiculous. So we do we assume that the even more complex activity of another organ, that we don't even share with other animals on this planet, is automatically going to be meaningfully similar?)

There's also a psychological point to be made about "big picture" arguments (the singularity, the Fermi paradox, the simulation argument, etc.) They have a tendency to converge on either prophetic religion-like conclusions (e.g. the singularity as the rapture for nerds) or Lovecraft (the estivation hypothesis, which was mentioned in a question and made me think about this.) When we talk about these things, there are many many unknowns. In such discussions, I think there is a tendency for the resulting arguments to resemble the internal contours of the human mind, more than any future events in the actual external world; hence their regression to religion-like conclusions. This does not mean such an argument must be incorrect, but it should make us suspicious when a big-picture argument hews too close to our "ontological test pattern. "

Consider in contrast cosmologists' models of the distant future of the universe, which concern physical objects which we can now observe and characterize, using rigorous mathematical rules. These models often seem boring, meaningless, difficult to understand, and unsatisfying. This is exactly how we should expect most models will seem of things outside our own and our ancestors' experiences, or beyond the scale of time and space to which we are accustomed and which we are built to perceive; the further outside their experience, the moreso. This occurred to me when we were discussing the estivation hypothesis, though overall Miller's arguments do not set off many alarm bells for this quick-and-very-dirty heuristic.

Origin of Life in RNA Computing: Independent Suggestion of Organic von Neumann Probes

Previously I had advanced the idea that, if intelligence has arisen elsewhere in the galaxy, it is likely to have colonized the galaxy in some form, and therefore we are more likely to find their artifacts here in our solar system than hear or understand their EM signals.  Specifically I argue that von Neumann probes are more likely to be entities of organic chemistry we find on low gravity bodies, that as natural selection is universal law that such entities - even if dispatched to gather information - would eventually be selected for fecundity; that is, they would inevitably become cancerous.  If the water that seeded the early Earth contained such entities, whether or not they were intact, the tumor detritis of these cancerous von Neumann probes would provide the template for life on ancient Earth.  

We have not nearly approached the amount of solar system exploration, or elaborated an abstract theory of how to recognize life or its artifacts, to be able to say we have absence of evidence.  Indeed we find nucleobases on asteroids, though so far we have no evidence so far that they originated from processes beyond the natural ones we are aware of.  

In a new paper, Hessameddin Akhlaghpour makes the observation that while the RNA information processing behavior of life on Earth is not Turing complete, with some additional (not implausible) molecular machinery, it would be.  He then argues that life originated with such a molecular machine and we have not yet found it.  (H/T Marginal Revolution)

Akhlaghpour H.  A Theory of Natural Universal Computation Through RNA.  arXiv:2008.08814

Profits From Asteroid Mining

After the very cool news showing pretty solid evidence that an asteroid breakup and bolide shower was likely responsible for the mid-Ordovician ice age (Schmitz et al 2019), I read about one candidate parent body (or what's left of it) for the L-type chondrites, 433 Eros. This article states that 433 Eros contains "...20 billion tonnes of aluminum and similar amounts of metals that are rare on Earth, such as gold and platinum."

So I set out to calculate the mineral value, based on current prices. For aluminum, I see bauxite cheapest at $50/ton. For gold and platinum, I couldn’t find values per ton of ore so I looked up the current prices (US$1533 and $955/oz resp. as of this writing) then look up average richness of the ores (1 oz/ton and 0.1 oz per ton resp.). Assuming similar richness in asteroid ores to deposits on Earth, would be over thirty-three trillion dollars, which is about 41% of the annual GDP of Earth. And that’s assuming an average 2% growth rate. (The article I linked to calculated twenty trillion, which it may have been closer to in 2014.) Granted, obviously the value will drop when there is suddenly an influx of valuable metals, but I'm assuming you're smart enough to leak the ore slowly and somehow get it to the surface with causing any repeat Chicxulubs.


A question and an observation:

1) How to get down to the surface? Gliders? Can you make gliders out of the (maybe partly processed) material that are disassembled at the surface? There are a number of established concerns that have gathered investors for this enterprise, but that I found, none of them has described how they would get material to the Earth's surface.

2) Most proposals involve mining the asteroids where they are, rather than bringing them nearer to Earth. There's actually a Wikipedia article with a good roundup and list of the companies, but that also points out that Osiris Rex will bring back 60g at a cost of 1 billion dollars.

3) At 2900 cubic kilometers, even if 433 Eros were a perfect sphere (which it's not) it would be just under 9 km to the farthest point from the surface. The deepest operating mine on Earth is South Africa's Ashanti Mponeng at 3.84 km deep. But on Eros, there would not be the same increase in heat and all the attendant problems of real gravity - so the proper comparison is to distance to the pit face. El Teniente in Chile is digging out a single (underground) road that is 17 km, and there are overall in that one mine 3,000 km of tunnels. Compare to Earth, which may have mineral deposits more than 4km below the crust, but we may never got to them - and past the crust, the inside of the planet is a waste because the mantle is molten and mixed. Of course the lay conception of asteroids as solid rocks is usually not correct, as most of them we've interacted with have been rubble piles barely held together by gravity.

4) I selfishly want asteroids to be mined in my lifetime because I believe that's where we'll find evidence of alien life - in the form of small mutant von Neumann probes made from organic chemicals.

An Existential Risk Comparable to the Singularity

Imagine that due to some breakthrough in computer science, we can determine (with certainty) that for a certain architecture, there are some designs that will "work"; that is, when activated, become a successful recursively self-improving general AI. Now assume that 13 such designs have already been tried. A tiny fraction to be sure; and yet in no case has there been any discussion before the research team turned each of them on, no input from other researchers, no public comment, and certainly no attention from policy makers of any sort.

The catch is that this architecture is highly iterative, and it has to run for a long time before you find out if it's going to "wake up" - consequently the researchers load the software and hardware into satellites, because the earliest any of them would "wake up" would be 2036. (For our purposes, assume once launched, these satellites are out of reach - like Elon Musk's car.)

I assume the AI safety community would have something to say about this; about people unilaterally turning on instances of this architecture, and placing it out of reach. Unlikely though it is, any one of those could wake up and we could find the Solar System transformed overnight, and not necessarily to humanity's benefit.

Why such an esoteric thought experiment? It's not really a thought experiment. There have already been 13 active attempts so far (that we know about) to signal nearby star systems. Given the constraint of the speed of light, the earliest we could hear back (or meet someone/something) from any of them would be 2036. Much like the satellite-launched AIs, once you send the message, you can't delete it from their inbox. The 1-in-29 million comes from the original Drake equation estimate of 3,500 civilizations in the galaxy, and one hundred billion star systems. Note that this thought experiment assumes every species is confined to one solar system, but if they have interstellar travel (and follow the signal back to the source) then that 1-in-29 million probability would be much higher.

AIs are at least designed by humans, with possible ethical constraints. Aliens able to visit our solar system would not in any way have our interests at heart. If you're in the rationalist community and you're concerned about a technological singularity, you should be very concerned about existential-risk-level-dangerous wildcat attempts to reveal our presence to other solar systems. This is called METI (Messaging Extraterrestrial Intelligence) instead of SETI, and you can read more about stopping it here.

Warm Spot on Europa Produces Plume

Image credit space.com

Current explanations for this warm plume (in fact, authors refer to it as a hotspot) are thermal inertia (basically, having higher specific heat than surrounding areas and so retaining heat longer than surrounding areas) or more excitingly, subsurface geologic activity - which would have implications for the evolution of life. Blog post here, paper here.

Trumbo SK, Brown ME, Butler BJ. ALMA Thermal Observations of a Proposed Plume Source Region on Europa. The Astronomical Journal, Volume 154, Number 4.

STOP METI

tl;dr if you worry about the singularity or bio-terrorism as an existential threat, you should help the effort to stop efforts to announce our presence to aliens. This should be a priority for the rationalist and effective altruism community.

Many people are familiar with the SETI project, Searching for Extraterrestrial Intelligence. METI stands for Messaging Extraterrestrial Intelligence. Stephen Hawking, Elon Musk, and Freeman Dyson believe this is incredibly stupid and dangerous.

Of the 13 (known) attempts to deliberately signal another star so far, the earliest that any response could be received is 2036. The earliest that any response could be received from a sun-like star with planets in the habitable zone is 2085. Additional attempts are almost certain to be made in the next few years.

Most scientists recognize how important - in fact, world-shattering - contact with aliens would be, and there's actually a protocol for what scientists should do if a message is received. But these attempts are being made by individuals or small groups, with no oversight, often with really stupid justifications. One was an art project; this one invited kids to compose the message.

The argument against deliberate messaging is that even here on Earth, contact between members of the same species with differing technology was catastrophic for not just the humans on one side, but the ecosystems. A visit from aliens with enough technology to detect us or visit would therefore likely be devastating, even if they don't have malicious intentions. Once we're detected, we can never be un-detected.

The arguments for METI are laughable, and best thought of in terms of a native American on the shores of the Atlantic, talking about building signal fires to bring the Europeans over even sooner. Their best arguments are:

• Aliens might already have noticed us anyway. (So why make it more likely?)
• It's extremely unlikely anyone will get the message (So why do it at all?)
• They won't come for a long time. (If we discovered a form of energy that would start poisoning our descendants in 10,000 years, would we use it?)
• If all the other aliens are remaining silent, then by doing the same, we're part of the problem, and we're hypocrites for trying to detect others (given the risk:benefit, that's a trade most of us would be comfortable making.)
• Aliens who can respond or come here will necessarily be moral beings and won't hurt us. (This one is really absurd, and not only makes assumptions about the intentions of the aliens, it sounds very much like a religious conviction.)

You can see a more thorough treatment of these arguments by a SETI expert in this paper, and the abstract finishes with these sentences: "Arguments in favor of METI are reviewed. It is concluded that METI is unwise, unscientific, potentially catastrophic, and unethical."

You can see some of these arguments being made with a straight face by METI's founder Doug Vakoch in this article. Note that METI is a splinter of SETI, since most of the scientists involved in SETI forbade active communication attempts.

Going forward I'm going to do my best to create awareness in the rationalist community and put priority on this as an existential threat alongside AI. My plan is to contact the people at SETI to see what they're already doing and how others can contribute. It seems like the best approach for now is stopping transmissions by blocking individual projects, but ideally there would actually be a law against this as well as norms that socially punish defectors. To end on an optimistic note: because there is a chokepoint (money and limited time on transmitters which are mostly controlled by universities) this problem is actually much more tractable than avoiding a "bad hard takeoff" of general AI.

More on the C. elegans that Survived Re-Entry During the Columbia Disaster

Living roundworms made it intact to the ground after the Columbia crash, as noted multiple times before (here and here.) There is more information in the article about their level of protection: "'They sustained some heat damage to exteriors, but that's about it,' Szewczyk said. The thermos-size metal container holding the nematodes was housed inside the locker of a crew compartment that was reinforced specifically to protect the materials inside. Once that compartment ruptured, however, the nematodes still survived the crash to Earth thanks to the locker's build, Szewczyk said. The C. elegans stayed alive upon impact because by the time that part of the shuttle fell to the ground, it had already decreased in speed, allowing the nematodes to touch down more gently." A locker is much less protection than being deep inside a solid chunk of rock.

This has obvious implications: "'From an astrobiology standpoint, the important thing was that if you had a multicellular organism going through the atmosphere you can have interplanetary transfer of life by natural means, and Columbia demonstrated that,' Szewczyk said. 'It was a fortunate thing to demonstrate that in the unfortunate circumstances that there were.'" Their descendants are kept at the University of Minnesota.

Could Modern Bacteria Seed Early Earth? Could Bacteria in Earth Ejecta Do the Same for Extrasolar Planets?

The C-index is this: how close would we have to be to an identical twin Earth to detect them with our SETI searches, given our current detection technology and our (their) emissions? Many argue that we would identify zero twin Earths this way because to detect them, they'd have to be within 3 LY or so - closer than the closest star.

But this post is asking a different question: if modern archaebacteria were seeded onto Hadean prebiotic Earth (say, an iron-sulfur species like the ones that our best guesses show were the last universal common ancestor of all life on Earth) - would they run rampant and colonize the whole world, or would they collapse, relying on some pre-existing network of metabolites produced by other cells? This is relevant to the question of passive colonization of simple organisms from Earth to nearby stars over arbitrary time scales. Archaebacteria in particular are a concern for NASA in terms of contaminating other planets.

This idea has been floated multiple times, including by astronomer and writer Fred Hoyle. Here is how the process of passive colonization could work. Asteroid impacts are sometimes powerful enough to eject surface material at greater than escape velocity. This is how we have over 100 fragments of Mars on Earth right now. If this happens, some bacteria may survive the initial shock, heat, then freezing and dehydration (some bacteria can survive these conditions; and in any event it doesn't have to be many.) Some of these meteorites will escape Earth orbit. If in vacuum and cold they're stable for arbitrarily long periods, they'll just accumulate in the solar system as septic Earth-meteorites over time. Some percentage of these fragments will interact with a solar system body (e.g. Jupiter) and be accelerated to solar escape velocity (like Oamuamua was in its native system.) Some percentage of those will enter another solar system (this is likely to happen once every 15 billion years, based on calculations inspired by Oamuamua.) Some percentage of these fragments will pass through a solar system with "primitive" planets with a liquid water-CO2 atmosphere like the early Earth. Some percentage of fragments will actually strike those planets, and some percentage of bacteria will make it to the surface intact.

Of course there are many unknowns and I only cited one number. We need to know the bacterial "burden" blasted out of orbit per unit time - none of those in our lifetimes, probably not even Tunguska; the percent chance of survival; the stability over time once frozen (being in solid phase is certainly not absolute protection against radiation). The frequency of planets is roughly known, but not the frequency of terrestrial CO2-water worlds, although reasonable bounds could be placed. As to surviving re-entry, this tends to raise the most eyebrows - but it's worth repeating that roundworms on the Columbia did in fact survive uncontrolled re-entry and were found alive on the ground weeks later. Inside a large iron-silicate rock they may be even better protected.

The most uncertain part of this list of attrition factors is the last one we've now come to, the chance of the bacteria fluorishing on the new planet (lack of metal ions for enzymes, or presence of cyanide, low volcanic activity if we're relying on the iron-sulfur archaebacteria; etc.) But we can start actually filling in the values for passive ("dumb") colonization - the equation to show how fast Fred Hoyle's "lifecloud" and Arrhenius's panspermia would actually occur. Note that this is a different concept from the organic von Neumann probes that could also unintentionally seed life as a side effect, although mechanics would be the same, and we would still be looking on watery low-gravity bodies for evidence of them, like comets and asteroids.

Initially I was tempted to make a stab at setting bounds on 50% chance of colonizing another star, but many of the probabilities would be just guesses. It's clear that this is quite a list of attrition factors, reducing the chance nearly to zero for any one cell or asteroid strike on Earth to seed a future alien ecosystem. But over geologic time there have been quite a few of these strikes, and assuming vacuum-frozen surviving bacteria are stable for a long time (a relative straight-forward thing to test), then the solar system has been slowly filling up with septic asteroids - some of which no doubt have been ejected. So for the near-term, this is unlikely to produce lots of passively seeded worlds, but over arbitrary time, the universe would be accumulating archaebacteria from every place that life evolved. If we think of the Sun as a second-generation main sequence star, then planets of third generation stars are more likely to have been seeded by second-generation ecosystems - and may have more metals available in the ashes of the second generation stars from which they're built.

Other quantitative predictions: a one-third chance of life on Europa.

Deoxyribose From Abiotic Space Conditions

Another biomolecule, the pentose sugar that serves as the backbone of DNA, quickly produced in un-directed synthesis under conditions that obtain on ice in space. Given the speed with which the first life formed on Earth (0.1 GA after the planet cooled to a solid form) as well as increasing evidence like this about how easy it is to make nucleic acid building blocks under prebiotic conditions, it's also very likely that life forms everywhere with water and carbon - even in ice. (See here for most recent panspermia/evolution post.)

Interstellar and Intergalactic Panspermia

Active colonization time estimates for the galaxy are invariably much shorter than the lifespan of the galaxy. Passive diffusion would take longer of course but empirically observed Oort cloud mixing intervals even this far from the core for the sun are on the order of 10^5 years. Lingam and Loeb (2018) calculate the delivery of amino acids between star systems but not timescales; still, they estimate an upper bound for the size of interstellar objects for our system (a 10 kilometer-radius asteroid) and Alpha Centauri (an Earth sized planet.) This is a second source pointing to the fact that we may be an interstellar backwater, uniquely un-exposed to evidence of replicators* relative to the stars around us.

Where intergalactic material transfer is concerned, of course given the distances involved we should expect the process to be slower, both in terms of at an absolute rate and moreso in terms of colonizing systems, since the ratio of number of incoming objects:number of systems to receive material will be quite low. That said, a) there are extragalactic stars in the Milky Way right now, and b) we're actually talking about an exponential rather than linear rate if there are replicators* of any sort being introduced. This excludes infrequent but massive events like intergalactic collisions, like those which the Milky Way has undergone repeatedly in the past.

*I deliberately use the term replicators as a catch-all to include "space-viroids" (most likely), von Neumann probes, "cancerous" (mutants selected for fecundity over original function) or otherwise, or deliberate colonizations by agents with some kind of intention (least likely.)

Ice Volcanoes on Ceres May Provide Replicators Means of Spreading

Extraterrestrial replicators (be they naturally-evolved, or von Neumann probes or the mutant descendants thereof) are at least as likely to be based on organic chemistry as on clanking iron-age technology, as is often imagined. Material returned from comet Wild-2 showed that it was actually an extraterrestrial comet, and had amino acids on it. Other investigations have shown the presence of nucleobases (the components of DNA and RNA.)

Even Arrhenius-style "panspermia" spread by passive diffusion on astronomical timescales is not implausible, as our Oort Cloud has mixed with close-passing stars' clouds on the order of once every 0.1 MA (and we should assume this happens to other stars as well.) However, for passively spreading replicators, higher-gravity bodies like planets or large moons are dead ends because they have no means of escaping the gravity well.



Water geysers on Enceladus, from space.com
This is why comets and wet carbonaceous asteroids are the best places to look, and why the Hayabusa-2 probe on Ryugu is so important. Same for the Dawn probe. Europa and even Enceladus may be a tough sell as passively escapable gravity wells, but now we see evidence of active water volcanoes on Ceres through its life span.

No Radio Signals from Oumuamua

To help rule out Oumuamua as an interstellar probe, it was investigated and found to have no detectable transmissions within 1-10 GHz down to powers of at least 300 milliwatts. Yes, this could be like an uncontacted tribe on Earth in 2018 saying that the drone that surfaced in their bay wasn't sent by people because it didn't give off smoke signals - but you have to start with clear assumptions of SOME kind and test them. That such a ship-like object is passing through the solar system is exciting, but since we found it very soon after we were first capable of finding it suggests that such objects pass through our solar system all the time.

Implications for Panspermia: Metazoans Can Survive Freezing Under Natural Conditions

Nematodes were frozen in Siberian permafrost 42,000 years ago, and were thawed in a lab, showing behaviors like feeding. This has implications for panspermia. In another unintentional experiments, other roundworms on the space shuttle survived uncontrolled re-entry and were found on the ground weeks after the accident. Stars regularly make close passes on time scales on the order of 100,000 years. 70,000 years ago, there was a star less than a light year away (Scholz's Star.) Large meteor strikes regularly (on geological timescales) send material into space. Are there thaw-able Earth nematodes (and many other things) now in order around Scholz's Star? There are definitely extraterrestrial objects in this solar system, but only in one case have we checked for biochemistry - and we at least found amino acids.

Look for RNA-World Rock Strata on the Moon

Schulze-Makuch and Crawford show in Astrobiology that that the Moon may have briefly been habitable - either (two options) about 4.5 billion years ago, or 3.5 billion years ago, for a few tens of millions of years, with an atmosphere and some liquid water (Gizmodo digest here.) Since the moon was formed after an impact with the early Earth, we should assume they had many of the same starting materials. The moon had less surface area and less time, and split from the Earth prior to even the earliest suggested prebiotic activity around 4 billion years ago, so it would have had to develop its own life - it could not have been "seeded."

The Moon with life (although terraformed.) From Techeblog.
Recent work by Tashiro et al suggest that a 4 billion year old rock stratum on Earth shows evidence of biological activity and may even be the fossil result of an RNA-World stage in the evolution of life on Earth. If it existed on Earth, it also could have existed on the Moon. It's not as though that rock stratum is exposed everywhere on Earth (the Tashiro people used samples from northern Labrador, Canada.) But it's interesting to think that the same stratum could have existed on the Moon if prebiotic chemistry took a similar course - and that those strata may be much easier to find and more widespread given the inactivity of the Moon relative to Earth.

Attempts at Interstellar Communication: Receipts and Responses Within Your Lifetime

tl;dr Lots of scientists are on record saying that broadcasting messages to nearby stars is dangerous. If you take other low-probability high-consequence existential risks seriously, you should consider joining the effort (resources here.) Compared to some of the problems the X-risk community is used to thinking about, it would be relatively easy to stop active SETI (METI) and protect the future of life on Earth.

A very philosophically-minded Native American in the pre-Columbian era, sitting on the beach at night, might have thought: there might be a beach just like this one, far across these waters. And if we set up large bonfires, we can let them know we're here! What a joy it would be to meet and exchange culture and technology! We know how the exchange actually played out; if it had come a few centuries earlier, it would have been the Norse landing in New England and Virginia, and likely would have been even worse. In any event, if our pre-contact philosopher would've known exactly how friendly those people across the water would be, he would've abandoned his plan.

This was the result of contact between two groups of the same species that had been briefly (in biological terms) separated. Based on simple evolutionary psychology, contact between two completely unrelated species would likely be much, much worse. But in contrast, revealing the strangely and hypocritically self-flagellating psychology of certain people, you don't have to look far for arguments that contact between humans and aliens would necessarily be beneficial to us - because we humans are so dirty and sinful (except for the people pointing out how sinful we are of course), and any aliens technologically advanced enough to visit us[1] would necessarily be morally advanced as well (again inconsistently, morally advanced as evaluated by the sinful human making the argument.) There's no valid argument in favor of METI, and every reason to think it should be considered suicide for Earth's entire ecosystem, not just for humans. And yet it's been done repeatedly, sometimes for reasons as silly as art projects.

Consider the following list of stars that have been targeted for such contact attempts, and which are close enough that a response (or a visit, if they can travel at light speed) could be received in the medically optimistic lifetime of someone born recently.

Star	Sun-like?	Planets?	Earliest Response
Teegarden's Star	red dwarf	possible	2036
GJ83.1	red dwarf (flare)	no evidence	2040
GJ273b	red dwarf	YES, SUPER EARTH IN HABITABLE ZONE	2043
Gliese 581	red dwarf	YES, POSSIBLY IN HABITABLE ZONE	2050
Altair	white (A)	no evidence	2051
GJ526	red dwarf (flare star)	unlikely	2059
HIP 4872	red dwarf	no evidence	2069
Kappa Ceti	YES, but frequent flares	no evidence	2069
HD 245409	cool orange/hot red dwarf (K-M)	no evidence	2077
55Cancri****	YES	YES, POSSIBLY IN HABITABLE ZONE	2085
HD 10307	YES	unlikely (companion)	2085
47 UMa**	YES	possible	2093
Gl 777	YES	possible	2103

*Where there are asterisks, numbers of asterisks = # of contact attempts

This is by no means an exhaustive list of all messages, only those for which we can receive a response by 2110 - and only those which are publicly reported.

The argument against active SETI (or METI; Messaging ET Intelligence) is simple. Any aliens which receive the message and have the ability to travel to our solar system are very likely far advanced. Whether or not they intend to harm us - if they, it, etc. even has "intentions" - is immaterial, as any contact with them is overwhelmingly likely to be catastrophic for Earth's ecosystem as a whole, including the human race. Arguments that the aliens will be (or for some reason must be) "nice" are comically narrow-minded and provincial.

The best arguments in FAVOR of active SETI appear to be 1) if we remain silent, then we can infer other species are likely to have made the same decision and it's inconsistent to remain silent but keep listening. 2) Advanced species probably already know about us, and these efforts don't much increase the chances of being detected.

To #1, even assuming the self-indication assumption-reasoning here doesn't demand bizarre causality as Nozick argued with respect to Newcomb's Paradox, given the likely severe consequences of a visit from a species more advanced than our own, I think joining in with all the silent species and being part of the problem (i.e., leading to the Great Silence) is quite a good trade. Notice that in our own ecosystem, most animals are quiet, unless they can quickly escape by flight or into burrows, are hidden by darkness, or are surrounded by conspecifics. Those of us who assume that aliens must be friendly somehow always insist that natural selection stops applying to advanced species and across interstellar space.

To #2, if the best argument really is that "they already know we're here so we're not increasing our chances of detection by potentially destructive aliens THAT much", which is literally the argument made by Jacob Haqq-Misra, Chief Scientific officer of the Lone Signal project, then that tells you a lot about how well-thought -through the whole enterprise is. What's more, it's absolutely false. The C-index is a quick and dirty measure of our detectability - if there were a twin Earth, giving off the same amount of electromagnetic noise that we are, how close would we have to be to detect it? Currently, about 3 LY, meaning we wouldn't even be able to hear ourselves from the next closest star. A powerful directed message on the other hand would be much easier to detect from a longer distance - so these messages are in fact likely increasing the probability of our detection substantially, at least at the target stars. Otherwise why are they even sending them?


These projects are ongoing. The problem has been discussed at conferences with approaches including a moratorium backed by international law (so far only talk.) These things are slow. One approach may be to go directly to the telescopes sending the messages, as there are a limited number of such installations. In decreasing magnitude of offense with those messages, they are:

Eupatoria (Crimea, Ukraine) - 7 targets, 11 transmissions
Arecibo (Puerto Rico, USA) - 4 targets, 4 transmissions
EISCAT (Tromso, Norway) 1 target, 1 transmission (an art project!)
Jamesburg (Carmel, California, USA) 1 target, 1 transmission (crowdfunded!!)

In addition, Alexander Zaitsev is a Russian astronomer who is far and away the individual most responsible for driving METI efforts. Douglas Vakoch is a METI proponent here in the US.

Lots of scientists are on record saying that broadcasting messages to nearby stars is dangerous. If you take other low-probability high-consequence existential risks seriously, you should consider joining the effort (resources here.) Compared to some of the problems the X-risk community is used to thinking about, it would be relatively easy to stop METI and protect the future of life on Earth.

[1] I purposely avoid the word civilizations, because that is a term which describes an entity with certain characteristics that humans can collectively form. Whatever activities groups of aliens form, it will not appear like any "civilization" we would recognize. "School", "herd", "flock", "swarm" are all terms that are at least as likely be useful to human impressions to describe the collective entities that we see.

Complex Organics from Enceladus

The work is driven by a chemical species that is hard to explain as other than the result of the reaction of these other complex molecules, and they build a model for how it's getting from inside Enceladus out into the plumes. Cassini detected it both in the E ring and the plume itself. Figure 10 from the paper (!!!):


Bonus points for one of the cooler names for a peer-reviewed paper ever. Points off for everyone who's touched this data and not noticed this before! What are you doing over there! You're giving fits to us bio/chemical types who are following this work. SciAm writeup here.


Frank Postberg, Nozair Khawaja, Bernd Abel, Gael Choblet, Christopher R. Glein, Murthy S. Gudipati, Bryana L. Henderson, Hsiang-Wen Hsu, Sascha Kempf, Fabian Klenner, Georg Moragas-Klostermeyer, Brian Magee, Lenz Nölle, Mark Perry, René Reviol, Jürgen Schmidt, Ralf Srama, Ferdinand Stolz, Gabriel Tobie, Mario Trieloff & J. Hunter Waite. Macromolecular organic compounds from the depths of Enceladus. Naturevolume 558, pages564–568 (2018)