In my last post,
Harvard's Galileo Project - The Systematic Scientific Search for Evidence of Extraterrestrial Technological Artifacts I explained how the observation of the strange motions of Oumuamua in 2017 caused Professor Avi Loeb at Harvard to launch the Galileo Project to look for evidence of alien Intelligences by searching for physical artifacts created by them. As opposed to using SETI radio telescopes, the Galileo Project intends to search for durable alien artifacts that could survive for billions of years in the depths of space. But there is another explanation for the very strange behaviors of Oumuamua that is well-covered by astronomer Christian Ready in the YouTube video at:
Oumuamua's mystery is finally solved!
https://www.youtube.com/watch?v=hKgnNG_si5E
That explanation calls for Oumuamua to be a pancake-shaped chunk of nitrogen ice that was blown off a Kuiper belt object like Pluto in another star system. We have never seen such an object produced by our own Solar System, so it seems rather strange that the very first object that we ever observed from a different star system should be so unique, especially since the second object to be seen from a different star system behaved just like an ordinary comet. We will just need to patiently stand by and wait to see what the Galileo Project observes over the coming years to form a better-informed judgment.
So we may still be left with the greatest remaining mystery in softwarephysics. Why, after more than 10 billion years of chemical evolution, do we not see any evidence of machine-based Intelligences within our Milky Way galaxy? In previous posts, I have suggested that the reason we do not find ourselves in a galaxy dominated by Intelligence is that carbon-based Intelligences always snuff themselves out once they discover the powers of science-based technology or because it might be harder to get carbon-based life started in the first place. For more on that see Urability Requires Durability to Produce Galactic Machine-Based Intelligences. In this post, I would like to add an additional constraint on the rise of machine-based advanced AI on a terrestrial planet. What if primitive carbon-based life is just as self-destructive as complex carbon-based life with Intelligence and science-based technologies?
Did Primitive Carbon-Based Life Prevent the Rise of Complex Carbon-Based Life on Mars?
There is a recent paper that makes just such a claim:
Early Mars habitability and global cooling by H2-based methanogens
https://arxiv.org/abs/2210.04948
Here is an interesting YouTube video by Antov Petrov that goes into the details of the above paper:
If Early Martian Life Existed, It Doomed The Planet, According to New Study
https://www.youtube.com/watch?v=z5V6O_DL5qA&t=0
According to the authors, the early climate of Mars was kept warm by the presence of the greenhouse gasses hydrogen and carbon dioxide in the atmosphere. The hydrogen gas greatly contributed to keeping the surface of Mars warm and wet. But if shortly after the very first prokaryotic carbon-based life arose on Mars it discovered how to metabolize the hydrogen and carbon dioxide gasses in the atmosphere to produce the waste greenhouse gas methane, the hydrogen gas would soon disappear causing the surface temperature of Mars to plummet into a Snowball Mars condition. It was all downhill for Mars from that time forward. The authors proposed that the simple prokaryotic life on Mars would then have to seek refuge in the crust of the planet. Indeed, it is estimated that about 15% of the Earth's entire biomass consists of simple bacteria in the cracks and pores of the rock deep in the Earth's crust. For more on that see:
Deep biosphere
https://en.wikipedia.org/wiki/Deep_biosphere#:~:text=The%20subsurface%20accounts%20for%20about,%2C%20annelids%2C%20and%20arthropods).
Below are some quoted extracts from the paper that give the gist of the author's hypothesis.
Introductory paragraph:
During the Noachian, Mars’ crust may have provided a favorable environment for microbial life. The porous brine-saturated regolith would have created a physical space sheltered from UV and cosmic radiations and provided a solvent, while the below-ground temperature and diffusion of a dense reduced atmosphere may have supported simple microbial organisms that consume H2 and CO2 as energy and carbon sources and produce methane as a waste. On Earth, hydrogenotrophic methanogenesis was among the earliest metabolisms but its viability on early Mars has never been quantitatively evaluated. Here we present a probabilistic assessment of Mars’ Noachian habitability to H2-based methanogens, and quantify their biological feedback on Mars’ atmosphere and climate. We find that subsurface habitability was very likely, and limited mainly by the extent of surface ice coverage. Biomass productivity could have been as high as in early Earth’s ocean. However, the predicted atmospheric composition shift caused by methanogenesis would have triggered a global cooling event, ending potential early warm conditions, compromising surface habitability and forcing the biosphere deep into the Martian crust. Spatial projections of our predictions point to lowland sites at low-to-medium latitudes as good candidates to uncover traces of this early life at or near the surface.
The best validation of our predictions would come from the discovery on present-day Mars of methanogenic life descending from the early metabolism modeled here. When run for atmospheric conditions corresponding to modern Mars our model predicts the atmosphere to be an insufficient source of electron donors for H2-based methanogens to survive. As Mars’ atmosphere became thinner during the Hesperian and early Amazonian, a putative biosphere persisting throughout the Noachian would have had to shift its main energy source from the vanishing atmospheric redox gradients to hydrothermal or radiolytic ones, deeper in the Martian crust. Deep chemotrophic ecosystems exist on Earth; an extant ecosystem on modern Mars might be of that kind, and could explain the repeated yet highly debated detection of CH4 traces in the lower Martian atmosphere. Our model could be adapted to quantify the habitability of modern Mars’ crust to such ecosystems and constrain their depth and productivity.
Our model does not take into account the biology-to-climate feedback specifically driven by albedo increasing with surface ice formation. As a consequence, our model likely underestimates the cooling effect of hydrogenotrophic methanogens on early Mars. This additional feedback could have amplified the direct atmospheric impact of methanogenesis on Mars climate and triggered a global glaciation. Although quantification of this effect warrants further development of Mars climate models, the mechanism in and of itself points to the possibility that life-environment feedbacks can compromise habitability at planetary scale. This Medean scenario (self-destructive life-planet feedbacks) adds conceptually to Gaian bottlenecks (life-planet feedback failing to counter the geophysical loss of habitability) as a potential limit to the long-term habitability of planets and planetary bodies in our solar system and beyond.
The authors go on to explain that the deeply buried biosphere of Mars could be responsible for the periodic observations of methane gas in the atmosphere of Mars.
The Case For Primitive Life on Mars
The above paper seems to favor the origin of carbon-based life on Mars in the brines of salty seawater. But current data also indicates that all of the necessary factors for the Hot Spring Origins Hypothesis of Dave Deamer and Bruce Damer were also present on Mars about 4.0 billion years ago. For a comparison of these two models see The Bootstrapping Algorithm of Carbon-Based Life and Urability Requires Durability to Produce Galactic Machine-Based Intelligences. The Hot Spring Origins Hypothesis maintains that fresh rainwater falling on the hydrothermal fields of volcanic islands are key to the rise of primitive carbon-based life on terrestrial worlds. Such terrains can cycle infalling organic molecular monomers into the polymers of carbon-based life and encase them in lipid protocells by means of wet-dry cycles that could be repeated millions of times at millions of locations all in parallel.
Figure 1 – Above is Bumpass Hell, a hydrothermal field on the volcanic Mount Lassen in California that Dave Deamer and Bruce Damer cite as a present-day example of the type of environment that could have brought forth carbon-based life on the Earth about four billion years ago.
Figure 2 – There certainly is evidence of early rivers on Mars carrying rainwater to salty seas.
Figure 3 – And we know that Mars certainly had a great deal of volcanic activity 4.0 billion years ago that would have generated volcanic hydrothermal pools containing fresh rainwater and organic molecules just like the Earth.
Figure 4 – Mars would have looked much like the Earth 4.0 billion years ago composed of a reducing atmosphere of hydrogen, carbon dioxide and nitrogen with salty oceans, volcanoes and volcanic hydrothermal pools filled with fresh rainwater and organic molecules just like the Earth.
Does Primitive Carbon-Based Life Frequently Prevent the Rise of Complex Carbon-Based Life?
That is what I would like to explore next by going back to Peter Ward's The Medea Hypothesis (2009) that I discussed in Is Self-Replicating Information Inherently Self-Destructive?. Peter Ward is my most favorite paleontologist, and I have read all of his books. His Medea hypothesis is the antithesis of the Gaia hypothesis. Gaia was the primordial Earth-goddess of the ancient Greeks, essentially the embodiment of a benevolent Mother Nature, and in the 1970s, James Lovelock and Lynn Margulis proposed that as a whole, the entire biosphere behaved in a coordinated manner that was beneficial to the ongoing existence of life itself. The Gaia hypothesis proposes that the biosphere as a whole manages to self-regulate the geophysical and geochemical processes of the Earth, by using negative feedback loops, in order to maintain the habitability of the Earth over billions of years.
In The Medea Hypothesis, Peter Ward proposes just the opposite. Medea was also a character in ancient Greek mythology, the wife of Jason of the Golden Fleece fame. When Jason abandoned Medea, she killed their two children as revenge, so Peter Ward rightfully thought that Medea represented just the opposite of the benevolent Mother Nature characterized by Gaia. In The Medea Hypothesis, Peter Ward proposes that because all forms of life in the Universe arise from the Darwinian processes of inheritance and innovation honed by natural selection, that necessarily, all living things in the Universe are selected for the ability to modify their home planets with positive feedback loops that enhance the survivability of the individual, not negative feedback loops that enhance the survivability of all. From Ward’s point of view, all living things resulting from Darwinian processes must necessarily select for living things that can self-replicate at all costs, with little consideration for their fellow beings sharing the resources of the planet, nor even for their own long-term survival. The urge to self-replicate at all costs necessarily leads to living things that outstrip their resource base through positive feedback loops.
For example, about 2.8 billion years ago cyanobacteria first arrived on the Earth. Even though the cyanobacteria were primitive forms of carbon-based life with no sign of Intelligence whatsoever, they still were able to develop a technology that changed the atmosphere of the entire planet. The cyanobacteria could photosynthesize sunlight, water, and carbon dioxide into sugars, releasing the toxic gas oxygen as a byproduct. Oxygen is a highly reactive gas and was very toxic to the anaerobic bacteria of the day. For example, today anaerobic bacteria must hide from oxygen at the bottoms of stagnant seas and lakes. But initially, these ancient anaerobic bacteria were spared from the Oxygen Catastrophe which took place 300 million years later (2.5 billion years ago) because first, all the dissolved iron in the oceans had to be oxidized and deposited as red-banded iron formations before the oxygen level could rise in the Earth’s atmosphere. Chances are that your car was made from one of these iron deposits because they are the source of most of the world’s iron ore. So you can think of your car as a byproduct of early bacterial chemical warfare that nearly killed off all life on Earth. Following the Oxygen Catastrophe, came the Huronian Snowball Earth glaciation, which occurred 2.4 to 2.1 billion years ago and is thought to have been induced by the oxidation of the greenhouse gas methane in the Earth's atmosphere. The Sun was about 24% dimmer 2.4 billion years ago, and with the loss of the methane blanket to hold in infrared photons the entire Earth seems to have frozen over.
Figure 5 – Above is a close-up view of a sample taken from a banded iron formation. The dark layers in this sample are mainly composed of magnetite (Fe3O4) while the red layers are chert, a form of silica (SiO2) that is colored red by tiny iron oxide particles. The chert came from siliceous ooze that was deposited on the ocean floor as silica-based skeletons of microscopic marine organisms, such as diatoms and radiolarians, drifted down to the ocean floor. Some geologists suggest that the layers formed annually with the changing seasons. Take note of the small coin in the lower right for a sense of scale.
Figure 6 – During the Huronian Snowball Earth glaciation, which occurred 2.4 to 2.1 billion years ago the entire planet was covered by ice.
But by far, the most disastrous of the Medean positive feedback loops caused by living things on Earth is the wholesale removal of carbon from the Earth’s surface. Peter Ward explains that living things are constantly sucking carbon dioxide out of the Earth’s atmosphere and converting it to calcium carbonate shells that are later deposited upon the sea bottom. As these carbonate deposits are subducted at the Earth’s subduction zones into the asthenosphere, some of the carbon is released by volcanoes as carbon dioxide, but most is lost to the Earth’s upper mantle, never to return to the Earth’s surface. This is certainly a bad long-term thing for carbon-based life, and Ward shows that within the next 500 – 1,000 million years, the level of carbon dioxide in the Earth’s atmosphere will decline below the level that complex multicellular plants can use for photosynthesis, and that will be the end of complex multicellular life on Earth. So the end of complex life on Earth will come from life itself and not from an increasingly brighter Sun, as described in most popular books. The game-changing paradigm shift of the Medea hypothesis, as opposed to the Gaia hypothesis, is that life on Earth as a whole is not necessarily acting in its own self-interest, so the solution to environmental problems may not simply be to remove mankind from the equation and let the biosphere return to its natural state. Instead, Ward suggests that some geoengineering is in order to extend the habitability of the Earth.
Figure 7 – Above are the famous White Cliffs of Dover. About 70 million years ago Great Britain and much of Europe were submerged under a shallow sea. The sea bottom was covered with white mud formed from the calcium carbonate skeletons of coccoliths. The coccoliths were tiny algae that floated in the surface waters and sank to the bottom during the Cretaceous period. These calcium carbonate layers were deposited very slowly. It took about 50 years to deposit an inch, but nearly 1500 feet of sediments were deposited in some areas. The weight of overlying sediments caused the deposits to become a form of limestone called chalk.
Figure 8 – Much of the Earth's surface is also covered by other forms of limestone that were deposited by carbon-based life forms. Much of the continental limestone gets buried in deep sedimentary basins to never be seen again or is metamorphosed into marble when it is pushed deep into the Earth at plate collision zones.
Is the Medean Hypothesis the Limiting Factor Preventing the Development of Galactic Machine-Based Advanced AI?
Given the above, I would now like to propose a new take on the Gaia and Medea hypotheses. The Gaia hypothesis proposes that all of carbon-based life on a planet comes together in a unified manner to deter the destructive astronomical, geophysical and geochemical perturbations that would otherwise end the existence of carbon-based life on a world. But the Medea hypothesis argues just the opposite. The Medea hypothesis argues that carbon-based life tends to be self-destructive in its pursuit of self-replicating at all costs with little concern for any deleterious side effects. But unlike the astronomical, geophysical and geochemical perturbations that could make an end to carbon-based life on a world, the perturbations to a world by even the most primitive forms of carbon-based life can be quite profound because carbon-based life can replicate in an exponential manner. One cell becomes two, which becomes four, which becomes eight...
In Urability Requires Durability to Produce Galactic Machine-Based Intelligences I introduced the new scientific term of urability:
Urability: A Property of Planetary Bodies That Can Support an Origin of Life
June 2022 - Dave Deamer, Francesca Cary and Bruce Damer
and explained that it took many billions of years of evolution for a carbon-based form of life to develop enough Intelligence to create a machine-based Intelligence that could then go on to explore our galaxy. Therefore, such urable worlds also need to be durable in that they need to remain habitable for many billions of years, and we keep finding new geophysical and geochemical factors that make that very difficult indeed. For example, in Is our Very Large Moon Responsible for the Rise of Software to Predominance on the Earth? we explored Anne Hofmeister's proposal that plate tectonics on the Earth was really driven by orbital forces from our very large Moon and not by convection currents at spreading centers or plate drag at subduction zones. In Could the Galactic Scarcity of Software Simply be a Matter of Bad Luck? we covered Professor Toby Tyrrell's computer-simulated research of 100,000 Earth-like planets that suggests that our Earth may be a very rare "hole in one" planet that was able to maintain a habitable surface temperature for 4 billion years by sheer luck.
Figure 9 – Toby Tyrrell's computer simulation of 100,000 Earth-like planets suggests that the Earth may be a "hole in one planet" proudly sitting on a fireplace mantle.
Figure 10 – Perhaps nearly all of the potential hospitable exoplanets that we are finding in our galaxy are not urable and cannot go the distance of staying habitable for billions of years.
Now, suppose the Gaia hypothesis has it all backwards? The Medea hypothesis proposes that even primitive carbon-based life will be selected for characteristics that make it self-replicate at all costs with no consideration of any deleterious side effects. Perhaps the Rare Earth (2000) of Peter Ward and Donald Brownlee might be caused by the limiting factors of astronomical, geophysical and geochemical perturbations acting on the Earth over billions of years that put a constraint on the exponential need for carbon-based life to self-replicate at all costs. Instead of carbon-based life miraculously responding in a Gaian manner to the insults caused by astronomical, geophysical and geochemical perturbations, perhaps it is the constraints placed on carbon-based life by these perturbations that compensate for, or dampen, the otherwise uncontrolled ambitions of carbon-based life to self-replicate and self-destruct. For example, perhaps it was actually fortuitous that our Sun on the main sequence increased in brightness by 1% every 100 million years over the past three billion years as its core accumulated waste helium nuclei because that offset the removal of the greenhouse gasses methane and carbon dioxide by carbon-based life on the Earth. Otherwise, the Earth might have remained in a Snowball Earth condition for most of the past few billion years.
Comments are welcome at
scj333@sbcglobal.net
To see all posts on softwarephysics in reverse order go to:
https://softwarephysics.blogspot.com/
Regards,
Steve Johnston
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