Possible life on Venus.

[Sky Captain]

The problem with Von Neuman probes is that the theory is based on overly simplistic assumptions that do not work in the real world. Namely the theory does not account for the distribution and accessibility of heavy elements needed for high technology, let alone self-replicating technology. We now know that there are many planets with masses in between that of Earth and Neptune, and those planets probably serve to trap much of the heavy elements of the universe underneath a much stronger gravitational field than that of Earth's. The self replicating probe idea requires the probe to constantly seek out sources of fuel and building materials, and find solutions to liberating those resources in order to make more probes. Which means we can compare it quite handily to living organisms. And you know what takes up the vast majority of a living organism's time? Eating! The probe and its offspring would have to contend with not only the vastness of space and surviving constant bombardment by cosmic radiation that could cause serious damage to its electronic brain-analogue (which in turn can be compared to damage to the DNA of a cell for self replication purposes), but it has no ability to identify the low mass objects like asteroids and dwarf planets that it needs to feed on from interstellar distances because of the same physical limitations our own telescopes have to put up with. So the idea of a single self-replicating organism analogue in space is actually pretty ludicrous. It needs an entire infrastructure of specialized machines like telescopes, computer brains, and probably specialized engines that resemble a partial Dyson swarm in order to actually propel itself from system to system in order to actually work.

I have always assumed an interstellar Von Neuman probe would be a fairly large autonomous factory starship containing maintenance bots, smaller robotic in system spacecraft that can do detailed geological survey of systems mapping promising asteroids and moons, deploy mining equipment and bring mined raw materials back to factory for refining and fabrication into spare parts, computer chips, new factory modules, engines, solar panels, more in system transport craft. It may take multiple decades or century for it to have built up enough infrastructure for commanding AI to contemplate starting fabrication of new Von Neuman probe.

A typical sci fi nanobot swarm that converts any material into more of itself is highly unrealistic.

As far as I'm concerned generalizations like this are so vague they are insufficient to answer the point. If we can't imagine something that actually requires the energy levels of a Type II or Type III civilization, the hypothesis is flawed on a conceptual level. We cannot assess the probability of finding an alien experiment unknowable to our own science.

Maybe experiments with bending of spacetime or wormholes or gravity or fabricating Kugelblitz black holes. That kind of stuff that we are fairly sure would require energy far above to what is available to us or even full Type I civilization.

I'm going to disagree with you there, just adding more collectors and radiators is very expensive in terms of mass penalty to the spacecraft its attached to.

For stationary or semi stationary applications it is perfectly fine to not to try to squeeze out every last percentage point of efficiency. Look at aircraft and cargo ships, engineers go to great lengths to design lightest aircraft reasonably possible while ships are just made of steel because it is cheap. Who cares if it burns a bit more cheap diesel fuel because it is not built from lightest carbon composites available. In a space setting equivalent to an ocean cargo ship may be a space habitat. While it may have fairly powerful engines it is not supposed to need a lot of delta v so mass and energy efficiency may be somewhere after durability, longevity, ease of maintenance and cost.

Ah, but lightsail starships of the type you are talking about are actually puny. We're talking about something that might very well be the size of a cell phone strapped to a sail the diameter of the moon (and thus far more massive than the payload even if we assume its ridiculously thin). There is no question why we aren't seeing these kinds of ships. Unless the ship is aimed directly at us so that we can see spillage from the laser driving it, its basically invisible.

Wouldn't it be far more than few hundred gram scale payload if you had exawatt scale lasers driving the sail IIRC there are real life proposals to send tiny gram scale light sail spacecraft out of our solar system using only GW class lasers. As far as visibility goes I think that would apply to any interstellar engine unless it is very close. A rocket based starship we would see across interstellar distance only if it's exhaust would be pointed directly at us.

[Bedlam]

Apart from potentially the materials they're made out of is there really a difference between Von Neuman probes and what we would currently consider biological life?

We don't know of anything biological which travels through space but making copies of its self from local resources is more or less a definition of life.

[Broomstick]

I think Von Neuman probes could be considered life. Actually, there's no reason they couldn't be partly organic. I suppose in a way organic life is a collection of Von Neuman devices. They certainly do blur the line.

[SolarpunkFan]

I think Von Neuman probes could be considered life. Actually, there's no reason they couldn't be partly organic. I suppose in a way organic life is a collection of Von Neuman devices. They certainly do blur the line.

Any sufficiently advanced machine is indistinguishable from biology?

As for partially organic von-Neumann probes? The astrochicken is what you're looking for.

[Bedlam]

Couldn't a crewed ship also fit the definition if the crew build new ships and crew them with their offspring? It might not be as quick a reproductive cycle as Von Newman probed are normally shown as but that's going to depend on how complex the probe it and what is technologically possible anyway.

[Solauren]

Yeah, a Von Newman 'ship' is possible.

Especially if the 'new' crew is grown using reproductive technologies (cloning, genetic engineering, accelerated growth), implanted with memories and skills, and then sent off on it's way.

[Sky Captain]

Some other thoughts about Von Neuman tech. It could plausibly happen that this tech or basis for it are developed because it would be incredibly useful in manufacturing, mining and space development. Maybe first steps would be largely autonomous asteorid mining equipment that can run without human supervision unless some unforeseen problem happens that requires human intervention. This is something that with cheap heavy lift rockets soon to be available could happen in not too distant future. Companies wanting to cut labor costs are highly interested in developing more and more automated factories. AI is another core tech that would be required for Von Neuman probe, however AI is incredibly useful almost everywhere so it could be developed even when no one initially seriously consider building Von Neuman probe.

Bottom line is core techs for Von Neuman probe are extremely useful almost everywhere. It could very well happen that at some point in the future some startup company realize that basis for building automated factories in space are already developed for applications on the ground and just need some repurposing.

I think Von Neuman probes could be considered life. Actually, there's no reason they couldn't be partly organic. I suppose in a way organic life is a collection of Von Neuman devices. They certainly do blur the line.

Any sufficiently advanced machine is indistinguishable from biology?

As for partially organic von-Neumann probes? The astrochicken is what you're looking for.

I think some mix of tech and biotech could also be possibility although currently it seems that tech is far more durable in space environment than biology. Humans need food, water, oxygen, pressurized living space, radiation shielding (electronics need too, but chamber for computer brain can be a lot more compact) while robots only need electricity to run which is easy to produce.

[Broomstick]

If your Von Neumann machines are for terraforming then you'd pretty much have to have some organic stuff, but it would probably be transported as seeds/spores/etc. rather than fully grown plants and animals until a destination for their work is reached and the organics are unpacked.

[Solauren]

With animals, you'd need a few adults to teach the young non-instinctive stuff, or at least refine it.

One possible method would be something akin to Terminators. Robots that look perfectly like a adult representative of the species they are pretending to be. The robot could be in power down mode, and then have skin grown and applied before the totally organic young are grown.

[TommyJ]

Wait for a second!
You are seriously discussing the Dyson orb trace and other markings that we believe are possible here on Earth.
But what if those technically and technologically advanced civilizations went a completely different path. Perhaps they were able to get energy in a way that our science still knows nothing about. Accordingly, it will not be able to define it as a technological footprint. The second option is that civilizations could develop along a different path. Spiritual. Find a way to live in harmony with their species and planet, without all that sh/t people have done.

[Jub]

Wait for a second!
You are seriously discussing the Dyson orb trace and other markings that we believe are possible here on Earth.
But what if those technically and technologically advanced civilizations went a completely different path. Perhaps they were able to get energy in a way that our science still knows nothing about. Accordingly, it will not be able to define it as a technological footprint. The second option is that civilizations could develop along a different path. Spiritual. Find a way to live in harmony with their species and planet, without all that sh/t people have done.

Tommy, I'm going to guess that you're pretty young and go easy on you.

The reason we don't assume those things is that we have no proof that they've happened and have no way to detect them if they have. Science doesn't work by jumping to conclusions based on NOT finding things, it asks questions and designs studies because of things it has already found.

[TommyJ]

I have always assumed that scientific methods are too narrow to suggest the possibility that current science has not even come close to possible ways of transferring energy and traveling intergalactic distances. Thanks to your comment, I can also understand that this does not depend on science, but on people who think too narrowly for the most part. And it is assumed that since we are going this way, then the advanced alien races should go this way. It seems that Neil DeGrasse Tyson was right when he said that the aliens looked at us and thought we were an undeveloped species.

[Solauren]

Tommy - from a philosopical stand-point, Science is someone going 'I don't understand how this works, I must figure it out, even if I makes me look stupid for not knowing before', followed by "I think I know how this works, I must prove it, even if I end up disproving myself and looking stupid."

As a result, science has to be 'open-minded'. One example I can think of like that was the experiment to prove that electricity and magnetism were unrelated. The experiment actually proved they were related. The scientist that conducted it (in front of a university class), admitted he was wrong, and further researched into it.

[bilateralrope]

I have always assumed that scientific methods are too narrow to suggest the possibility that current science has not even come close to possible ways of transferring energy and traveling intergalactic distances.

If we assume that aliens are doing things human science can't even predict, we run into a practical question: What should we be looking for to detect them ?

I can't think of anything more specific than "some phenomena we can't explain". But detecting an unexplained phenomena doesn't say anything beyond it being an unexplained phenomena. We can't jump from seeing an unexplained phenomena to assuming it's a life signature.

Phosphine is a different story. We know what it looks like. We have a list of things that produce it, and the only thing on that list that could exist in the atmosphere of Venus is life.

It's the same with radio waves. We know what stellar phenomena can produce them and what those look like. We can identify signals we generated. So, if there are any left after excluding those, that means alien intelligence.

Though it's quite telling that, when talking about how close an alien civilization would have to be, they talk about signals of the strength of Arecibo or stronger. We aren't producing signals that strong right now and I don't know if radar astronomy is valuable enough for us to be doing so again any time soon.

One example I can think of like that was the experiment to prove that electricity and magnetism were unrelated. The experiment actually proved they were related. The scientist that conducted it (in front of a university class), admitted he was wrong, and further researched into it.

I'm not familiar with that one. But I use the story of the Argo spot to make that point.

At the beginning of the 19th century, the idea that light does not simply propagate along straight lines gained traction. Thomas Young published his double-slit experiment in 1807. The original Arago spot experiment was carried out a decade later and was the deciding experiment on the question of whether light is a particle or a wave. It is thus an example of an experimentum crucis.

At that time, many favored Isaac Newton's corpuscular theory of light, among them the theoretician Siméon Denis Poisson. In 1818 the French Academy of Sciences launched a competition to explain the properties of light, where Poisson was one of the members of the judging committee. The civil engineer Augustin-Jean Fresnel entered this competition by submitting a new wave theory of light.

Poisson studied Fresnel's theory in detail and, being a supporter of the particle theory of light, looked for a way to prove it wrong. Poisson thought that he had found a flaw when he argued that a consequence of Fresnel's theory was that there would exist an on-axis bright spot in the shadow of a circular obstacle, where there should be complete darkness according to the particle theory of light. Since the Arago spot is not easily observed in everyday situations, Poisson interpreted it as an absurd result and that it should disprove Fresnel's theory.

However, the head of the committee, Dominique-François-Jean Arago (who incidentally later became Prime Minister of France), decided to perform the experiment in more detail. He molded a 2 mm metallic disk to a glass plate with wax. He succeeded in observing the predicted spot, which convinced most scientists of the wave nature of light and gave Fresnel the win.

[TommyJ]

Thanx Solauren and
bilateralrope for your explanation.
And to the previous commentator.
I understand how science works.
And I agree with all your arguments. In the original post, the problem was that I was in a bad mood and couldn't get the message across.
I am interested in the mechanism how we recognize a life form that we cannot understand. And I have no doubt about life on Venus. What it is. Although, based on our knowledge of life, it is unlikely that in the atmosphere
intelligent life can arise. But our knowledge at the moment is not enough to say that this cannot be so.

[Broomstick]

Life would not have to originate in the atmosphere if there was an earlier period in Venus's history when it was more hospitable, life became established, then was killed off everywhere but the atmosphere when the greenhouse effect went berserk and heated the place up to the current temperature.

[Jub]

The other thing about Venus is that the gas could just be a chemical reaction with material on the surface. That planet has some nasty chemistry going on all over it and we know very little about what's going on at the surface level and below.

[TommyJ]

Life would not have to originate in the atmosphere if there was an earlier period in Venus's history when it was more hospitable, life became established, then was killed off everywhere but the atmosphere when the greenhouse effect went berserk and heated the place up to the current temperature.

Yes, your option is possible. But imagine how great it would be to find out that life can still appear in other conditions.
We just don't understand yet how this is possible.
In the event of such a discovery, this could open up new, completely amazing prospects for the search for extraterrestrial life. Perhaps it is precisely the confirmation that life has other forms - this is exactly what we need now.

[SolarpunkFan]

Further update.

Purported phosphine on Venus more likely to be ordinary sulfur dioxide, new study shows

In September, a team led by astronomers in the United Kingdom announced that they had detected the chemical phosphine in the thick clouds of Venus. The team's reported detection, based on observations by two Earth-based radio telescopes, surprised many Venus experts. Earth's atmosphere contains small amounts of phosphine, which may be produced by life. Phosphine on Venus generated buzz that the planet, often succinctly touted as a "hellscape," could somehow harbor life within its acidic clouds.

Since that initial claim, other science teams have cast doubt on the reliability of the phosphine detection. Now, a team led by researchers at the University of Washington has used a robust model of the conditions within the atmosphere of Venus to revisit and comprehensively reinterpret the radio telescope observations underlying the initial phosphine claim. As they report in a paper accepted to The Astrophysical Journal and posted Jan. 25 to the preprint site arXiv, the U.K.-led group likely wasn't detecting phosphine at all.

"Instead of phosphine in the clouds of Venus, the data are consistent with an alternative hypothesis: They were detecting sulfur dioxide," said co-author Victoria Meadows, a UW professor of astronomy. "Sulfur dioxide is the third-most-common chemical compound in Venus' atmosphere, and it is not considered a sign of life."

The team behind the new study also includes scientists at NASA's Caltech-based Jet Propulsion Laboratory, the NASA Goddard Space Flight Center, the Georgia Institute of Technology, the NASA Ames Research Center and the University of California, Riverside.

The UW-led team shows that sulfur dioxide, at levels plausible for Venus, can not only explain the observations but is also more consistent with what astronomers know of the planet's atmosphere and its punishing chemical environment, which includes clouds of sulfuric acid. In addition, the researchers show that the initial signal originated not in the planet's cloud layer, but far above it, in an upper layer of Venus' atmosphere where phosphine molecules would be destroyed within seconds. This lends more support to the hypothesis that sulfur dioxide produced the signal.

Both the purported phosphine signal and this new interpretation of the data center on radio astronomy. Every chemical compound absorbs unique wavelengths of the electromagnetic spectrum, which includes radio waves, X-rays and visible light. Astronomers use radio waves, light and other emissions from planets to learn about their chemical composition, among other properties.

In 2017 using the James Clerk Maxwell Telescope, or JCMT, the U.K.-led team discovered a feature in the radio emissions from Venus at 266.94 gigahertz. Both phosphine and sulfur dioxide absorb radio waves near that frequency. To differentiate between the two, in 2019 the same team obtained follow-up observations of Venus using the Atacama Large Millimeter/submillimeter Array, or ALMA. Their analysis of ALMA observations at frequencies where only sulfur dioxide absorbs led the team to conclude that sulfur dioxide levels in Venus were too low to account for the signal at 266.94 gigahertz, and that it must instead be coming from phosphine.

In this new study by the UW-led group, the researchers started by modeling conditions within Venus' atmosphere, and using that as a basis to comprehensively interpret the features that were seen—and not seen—in the JCMT and ALMA datasets.

"This is what's known as a radiative transfer model, and it incorporates data from several decades' worth of observations of Venus from multiple sources, including observatories here on Earth and spacecraft missions like Venus Express," said lead author Andrew Lincowski, a researcher with the UW Department of Astronomy.

The team used that model to simulate signals from phosphine and sulfur dioxide for different levels of Venus' atmosphere, and how those signals would be picked up by the JCMT and ALMA in their 2017 and 2019 configurations. Based on the shape of the 266.94-gigahertz signal picked up by the JCMT, the absorption was not coming from Venus' cloud layer, the team reports. Instead, most of the observed signal originated some 50 or more miles above the surface, in Venus' mesosphere. At that altitude, harsh chemicals and ultraviolet radiation would shred phosphine molecules within seconds.

"Phosphine in the mesosphere is even more fragile than phosphine in Venus' clouds," said Meadows. "If the JCMT signal were from phosphine in the mesosphere, then to account for the strength of the signal and the compound's sub-second lifetime at that altitude, phosphine would have to be delivered to the mesosphere at about 100 times the rate that oxygen is pumped into Earth's atmosphere by photosynthesis."

The researchers also discovered that the ALMA data likely significantly underestimated the amount of sulfur dioxide in Venus' atmosphere, an observation that the U.K.-led team had used to assert that the bulk of the 266.94-gigahertz signal was from phosphine.

"The antenna configuration of ALMA at the time of the 2019 observations has an undesirable side effect: The signals from gases that can be found nearly everywhere in Venus' atmosphere—like sulfur dioxide—give off weaker signals than gases distributed over a smaller scale," said co-author Alex Akins, a researcher at the Jet Propulsion Laboratory.

This phenomenon, known as spectral line dilution, would not have affected the JCMT observations, leading to an underestimate of how much sulfur dioxide was being seen by JCMT.

"They inferred a low detection of sulfur dioxide because of that artificially weak signal from ALMA," said Lincowski. "But our modeling suggests that the line-diluted ALMA data would have still been consistent with typical or even large amounts of Venus sulfur dioxide, which could fully explain the observed JCMT signal."

"When this new discovery was announced, the reported low sulfur dioxide abundance was at odds with what we already know about Venus and its clouds," said Meadows. "Our new work provides a complete framework that shows how typical amounts of sulfur dioxide in the Venus mesosphere can explain both the signal detections, and non-detections, in the JCMT and ALMA data, without the need for phosphine."

With science teams around the world following up with fresh observations of Earth's cloud-shrouded neighbor, this new study provides an alternative explanation to the claim that something geologically, chemically or biologically must be generating phosphine in the clouds. But though this signal appears to have a more straightforward explanation—with a toxic atmosphere, bone-crushing pressure and some of our solar system's hottest temperatures outside of the sun—Venus remains a world of mysteries, with much left for us to explore.

Apologies if this is a necro.

[Formless]

phys.org is an extremely slow, low detail, and not entirely reliable source. The original authors have already seen this paper and say already ruled out the possibility of it being sulfur dioxide in the original paper and in a new paper they are planning to release. The problem is that when they went for an "open science" approach, they were expecting other labs to contact them first for clarification on their data and methods section rather than the dogpile of attempted debunking that actually happened. While its not wrong per-say of other labs to do it this way, you have to remember that the original team is fairly small, making it hard for them to keep up with all the scientists who are itchy to jump on a radical proposal, as explained in this interview with the lead scientist behind the phosphine claim.

[SolarpunkFan]

My apologies, then.

[teodor95]

I don`t think it`s possible. That point probably has already been mentioned here that high preassure and high temperature make life existence on the surface of Venus impossible. However, I assume that life can exist on Mars. I made such kind of conclusion because as all of you probably may know that water ( ice ) was found on the surface of the red planet. So I guess some forms of life can remain in this ice

[bilateralrope]

I don`t think it`s possible. That point probably has already been mentioned here that high preassure and high temperature make life existence on the surface of Venus impossible.

Did you even read the article quoted in the opening post of this thread ?

Nobody was talking about life on the surface.

[JackWhite]

Thanks for posting this material. Interesting stuff there but we have to see when and how it goes. Time will show everything