Much thought has been devoted to the idea of life beyond Earth. While it is often assumed that life both on Earth and on other planets must have arisen independently, their origins separate, the panspermia hypothesis offers an alternative view, that life is not confined to planets but rather is distributed throughout space and fills the cosmos, spreading, growing, and evolving whenever it finds an environment, such as a planet, it can thrive in.
Lithopanspermia: Panspermia through Meteors
The most common form of panspermia proposed is “lithopanspermia”, which posits that after a meteor impact of a life-bearing planet, various rocks ejected from the impact site with enough energy to reach escape velocity could contain microbial life. It might sound crazy to think any life-form could survive such an impact but the evidence in favor of the possibility is more robust than one might think. As far as anyone knows microbes such as bacteria could survive such an impact.
Launched into space, the high levels of radiation and even the vacuum itself do damage the microbes, but if shielded by a large rock, a few meters wide or wider, there is no reason to suppose microbes couldn’t survive for periods long enough for the natural course of the rock’s orbit to have an excellent chance of colliding with another planet. The discovery of interstellar asteroids like Oumuamua and comets like Borisov has confirmed that such material links exist not only between planets but between whole solar systems as well. After impacting the new planet, if the environment is favorable for its growth the microbes will spread and grow, colonizing the new world.
Exactly this is what some believed happened to Earth early in its history, most likely after the oceans first formed, providing a favorable environment for carbon-based water-drinking life. Whether Earth’s life originally came from the planet or from abroad depends on the likelihood of seeding via panspermia and the likelihood of abiogenesis, both of which, especially the second one, are currently unknown.
If abiogenesis is rare, perhaps unique, but panspermia is common then it’s very probable that Earth’s life originated through panspermia. If, on the other hand, abiogenesis is common but panspermia is rare then it’s probable Earth’s life originated through abiogenesis. It’s also possible, of course, that they are equally rare or equally common, in which case the picture would be much more muddled.
Horizontal Gene Transfer and ongoing Panspermia: Alien Genes?
Muddling the picture still further is the possibility of life arising by abiogenesis and life coming in from space simultaneously. If they are otherwise similar, e.g. carbon-based, water-drinking, DNA-using life-forms, then horizontal gene transfer could probably occur despite their different origins.
It already occurs on Earth across the boundaries of the “domains” of life, and is relatively limited; however, it’s possible that it was much more important and widespread in earlier and more primitive life-forms. In this case the answer to the question “panspermia or abiogenesis?” would be “both”, because indigenous and migrant life would have formed a hybridized population that went on to be the ancestors of all subsequent life on the planet, including us and our whole ecosystem.
There’s no particular reason to suppose this process would have ceased after the earlier part of Earth’s history. If the genes of incoming life-forms are compatible with existing life on Earth, alien genes could be inserting themselves into terrestrial species even now. How many of the genetic changes we assume are mutations are actually the transfer of extraterrestrial DNA?
DNA pouring into Space: Proof of Panspermia?
Although this whole idea might sound insane to some people, in 2018 a Russian research team found DNA on the exterior of the International Space Station that is similar to that found in Barents and Kara Sea microbes. Since low Earth orbit, as the saying goes, is halfway to anywhere, it’s reasonable to assume the DNA could escape Earth orbit altogether and be flung toward various other locations in the universe.
The researchers propose that the global atmospheric electrical circuit is the mechanism that drives the launch of microbes and DNA from Earth into space. It’s worth noting that if microbes and DNA can come out of the Earth and into space, it’s reasonable to assume that microbes and DNA can also come out of other planets and onto Earth, a possibility acknowledged by the researchers.
Radiopanspermia: Panspermia through Starlight
This brings us to a more interesting but perhaps less likely form of panspermia: “radiopanspermia”. In contrast to “lithopanspermia”, which depends on microbes being embedded in rocks that are launched by impacts, and more speculatively other mechanisms such as volcanic action as well, “radiopanspermia” proposes that bacterial spores themselves could be lifted from the upper atmosphere to low orbit, and from there be pushed by radiation from the sun and stars to destinations abroad.
It’s a romantic and elegant theory, but how likely is it? As early as 1903 Svante Arrhenius demonstrated that particles below a critical size, 1.5 micrometers, would be propelled by the sun’s radiation up to high speeds, the smaller the particle the faster the speed, suggesting that single bacterial spores would fare the best through this method of natural spaceflight.
Unfortunately it turns out that ultraviolet radiation damages bacteria to the point of death and breakdown of DNA at an extremely high rate, leaving the overwhelming majority of microbes dead by the time they could reach another planet, let alone another solar system or galaxy.
That’s not quite the end of the story, however, since whether microbes could make it depends not just on the probability of survival but on how many microbes are being transmitted out, which in Earth’s case we don’t know with a great deal of certainty. If only one in a billion microbes survive a given trip but a quadrillion microbes are sent on that trajectory, there’s still a lot of life left at the end of the journey that could seed the destination planet. It has been argued that sheer numbers might make radiopanspermia viable after all.
The odds of survival are far greater, though, if even minimal shielding through rock or dust surrounds each spore. This is technically a form of lithopanspermia, but just enough rock to shield one spore, a phenomenon that probably occurs through natural processes with some regularity, could still be more than small enough to be propelled by radiation pressure a la radiopanspermia.
Panspermia through Comets
Some of these shielded spores might be gravitationally captured by passing comets and incorporated into their own bodies, perhaps with spores radiating out from cometary bodies through tails of comet dust when they enter inner solar systems, surviving, shielded from harsh radiation by comet dust, more than long enough to land in the friendly waters of a new planet.
Indeed, comets are an under-rated site for extraterrestrial liquid water and for life in general. In the first million years after comets are formed in a given solar system, including our own, their interiors were warm enough for water to be liquid. Comets have all the ingredients considered to be necessary for life as we know it, and there’s every reason to believe that life could thrive in the interiors of comets if they were liquid.
For all we know life could either form abiogenically in a comet interior or be seeded from elsewhere and multiply, spreading through dusty cometary tails to other bodies friendly to life. Before the comets froze over they could have migrated to places such as the outer moons of the solar system, which had liquid water surfaces early in their history, and then places like Mars once they cooled enough to permit oceans to form, followed by Venus and Earth.
It’s worth noting that of all the planets (and planet-sized moons) of our solar system, life could most easily spread throughout the solar system from Enceladus, because of its small mass and low gravity. Comets have a far easier time transferring material on and off their surfaces than even the smallest planets. If life was seeded in or ever arose independently on comets, then they were likely the first environments in our solar system to host life.
As Comet Borisov demonstrates such bodies can also travel over interstellar distances, making them one of the best vectors for panspermia. Through this mechanism alone life could spread throughout the cosmos given sufficient time.
Panspermia through Natural Electromagnetic Propulsion?
More exotic processes have also been proposed. Earth’s magnetosphere, like most such structures, develops and ejects from itself “plasmoids”, coherent structures of plasma and magnetic fields, which might in some cases be ejected at very high speeds toward other solar systems. If microbial spores lifted into the uppermost parts of the atmosphere are caught in one of these magnetic bubbles, they could be brought along for the ride, effectively using a form of naturally-occurring electromagnetic propulsion to reach new planets.
Where this helps the panspermia hypothesis is the fact that much less time is needed to cross the void between stars using this method than using radiation pressure, thus leading to far less cumulative damage from harsh radiation and far greater odds of surviving the journey. This mechanism might be sufficiently robust to account for a good portion of the panspermia that does take place, assuming we’re ever able to prove the hypothesis.
Pseudopanspermia: Already scientific Fact
Although conclusive evidence of panspermia remains elusive, we do have conclusive evidence of what’s called “pseudopanspermia”, the transmission not of life-forms themselves but of the building blocks of life. Complex organic molecules are surprisingly common in outer space in a wide variety of environments, ranging from the atmospheres and interiors of planets to the darkest interstellar voids.
The complexity of these molecules scientists are discovering seems to become more and more remarkable all the time. In 2013 an experiment demonstrated that dipeptides, the building blocks of proteins, can be created in interstellar dust. In 2016 amino acids were detected in the coma of Comet Churyumov-Gerasimenko. Perhaps most remarkably of all, a group of scientists studying one of the Allende meteorites claim in 2020 to have discovered an entire protein of extraterrestrial origin within the meteorite.
How complex are the organic compounds that exist in outer space, within comets and within meteorites? If we find anything all that much more complex than what we’ve found so far, which basically means DNA and life itself, then not only pseudopanspermia but also true panspermia would become a scientific fact. We’ll have to see about that, though!
Deep Time’s Influence on Panspermia
Another topic that is not often thought about, that affects the prevalence of panspermia, is the age of life in the universe. If Earth was the first genesis of life in the cosmos then life has only had 4 billion years, about a third of the age of the universe, to spread. Life could easily have spread across intergalactic distances in that time, but still it would be only a small fraction even of the visible universe, let alone anything beyond that.
If, on the other hand, life arose early in the universe’s history, it could have had twice or possibly as much as three times as long to spread. The oldest known planet, PSR B1620-26 b, nicknamed “Methuselah”, is almost 13 billion years old, so it’s reasonable to assume that there were bodies in the cosmos capable of generating life that early. This far back distances were considerably closer than they are now due to all the expansion of space that’s taken place since then, so life could have spread over a very wide area if it got started back then.
The Habitable Epoch of the Early Universe
Perhaps most wildly of all, it has been speculated that life could have arisen far earlier, as early as 10 million years after the Big Bang. This was after the universe had ceased being opaque, and the background temperature from cosmic radiation left over from the Big Bang, today a chilly 3 Kelvin, was warm enough to be compatible with liquid water. In principle life could have existed anywhere in space. Now that’s some panspermia worthy of the name!
A big issue with this idea is that Big Bang Nucleosynthesis did not produce the heavier elements in the quantities needed for life as we know it. This idea, however, posits that a sufficiently dense pocket of the universe could have formed a star that synthesized the heavier elements such as carbon and oxygen in its core.
After it went supernova (early stars are thought to have been massive and so would have had short life spans) these heavy elements would have been dispersed to life-bearing bodies such as planets, though it could in principle have been comets as well or even possibly free space if there wasn’t much high-frequency radiation in the vicinity.
Panspermia and Intelligence in the Early Universe
This “habitable epoch” of the universe would have lasted for a bit over 6 million years, which might have been enough time for life as we know it to emerge. If carried off from its ancestral environment, it could have, though sequestration in the depths of asteroids and comets, survived long enough to seed the oceans of the first generation of stars when they started to form en masse, possibly even being the ancestors of life on Earth. Given the enormous expansion of space since then these life-forms could have been dispersed over an extremely wide area.
While it’s considered highly unlikely that an intelligent civilization could have evolved in just 6 million years, we really don’t know how quickly an intelligence could emerge. In principle it might be feasible for complex and even sapient life to have evolved in such an environment. Their civilization or what’s left of it might be out there somewhere even now, having been living witnesses to over 13 billion years of cosmic evolution. The kind of technological and scientific knowledge they could have developed over such an extreme length of time could prove breathtaking to say the least.
Exotic Life: Quarks and Nuclear Forces?
Of course any good science fiction author or worldbuilder would know that there are possibilities more exotic still. Although very speculative, there is no reason in principle to suppose that life couldn’t be driven by exotic processes that don’t rely on molecules, perhaps utilizing particles at the subatomic or fundamental level. Instead of electromagnetic forces like we use these life-forms might use nuclear forces.
What’s really fascinating about this is that the universe was very hot and dense shortly after the Big Bang, with a great abundance of energy, perhaps leading to a perception of time far more compressed than our own. The amount of work that could be completed in such an environment in a fraction of a second would take many years in a lower-energy environment like our own.
When could such exotic forms of life have arisen? I’m no expert on the topic, so I wouldn’t venture any definite answers. I will note periods of time that might be interesting for the purposes of real-world scientific or philosophical speculation or (perhaps more fruitfully at this time) science-fictional worldbuilding.
The Cosmic Nuclear Fusion Reactor
Before the habitable epoch, an interesting period was “Big Bang Nucleosynthesis”, when the entire universe was a nuclear fusion reactor, between 2 and 20 minutes after the Big Bang. During those 18 minutes large amounts of helium were synthesized, accounting for the supply we see today, plus a small amount of lithium. Tiny amounts of carbon, nitrogen, and oxygen were formed as well, but the amount of these elements was negligible. The reason for this is that these elements take thousands of years to synthesize in abundance, and there was only 18 minutes of reaction time before the universe became too cool.
Still, if there was an exceptionally dense pocket of these heavier elements for whatever reason, that could provide an alternative genesis of life as we know it during the “habitable epoch” a few million years later, without needing to resort to a freakishly early star forming.
Exotic forms of life could have arisen in this cosmic reactor, and for all we know 18 minutes could have been enough time for the rise and fall of a whole civilization, though it’s not inconceivable they might have left some sort of legacy (possibly leading to “directed panspermia”, deliberate seeding of life) or even transformed or saved themselves in such a way as to survive their own version of “heat death of the universe”.
It’s also worth noting that photons, i.e. light, dominated the universe during this period, starting 10 seconds after the Big Bang, to the extent that the universe was opaque for the first 370,000 years of its existence. Could that have been fruitful ground for life-forms based on radiation? If so they might still be out there, with incomprehensible powers and imperceptibly slow metabolism, even now. That’s an interesting thought.
The Quark Era
Another interesting period is the era after the fundamental forces had decoupled from each other and assumed their present forms, but before temperatures had cooled enough to allow anything other than a plasma composed of quarks, gluons, leptons, and their antimatter counterparts to exist. This was between 10−12 and 10−12 seconds after the Big Bang. That small fraction of a second might seem small to us, but to any life-forms, based upon quarks and gluons instead of molecules, accessing the extreme energies of that era it might have seemed like an eternity.
Before the quark era physics as we know it breaks down, as several of the fundamental forces were merged, and thus in preceding eras any ideas become much more speculative.
Cosmic Inflation
In particular the greatest event in this period that we think happened is cosmic inflation, when in a tiny fraction of a second the universe expanded by at least 78 orders of magnitude, possibly far more than that. That’s equivalent to a nanometer of distance expanding to 10 light-years. Space expanded so fast during this period it outpaced the speed of light.
This event is mysterious enough that a science fiction author or worldbuilder could postulate that an exotic form of intelligent life before the time of cosmic inflation might have attained mastery of the forces of nature and of the universe, in much the same manner as speculated in a previous post, and deliberately induced the inflation for some unknown purpose, directing the development of our physics and environment toward what we saw later. Not very scientific, but it is a cool idea.
The Planck Era: Beyond Physics as We know It
Some models of cosmology posit a “Planck era”, 10−43 seconds (the Planck time) after the Big Bang and earlier, where all the fundamental forces were unified into one force and subatomic particles as we know them could not form. Presently-known physics cannot be used to ascertain what the universe was like during this period; it is thought that the quantum effects of gravity dominated the universe in this era, but since we lack a quantum theory of gravity our knowledge of what those effects were is speculative at best.
It is conceivable that forms of life that are based on the energies that pervaded the universe during this era, at almost incomprehensibly high temperatures and densities, and on quantum-gravitational forces could have arisen, living out their whole life cycle in what to us would be an infinitesimal time.
The Omega Point and the Alpha Point
Who knows what sort of powers or abilities an intelligence that evolved during this era would possess? The abilities such an intelligence could manifest in the beginning of time could be compared to the Omega Point first proposed by Pierre Teilhard de Chardin. In Tielhard’s version the god-like universal intelligence, which he indeed compared to the Christian God, occurs at the end of the universe, later dubbed the “Big Crunch”, where everything in today’s cosmos is drawn into one singularity at the edge of time.
In this version, the god-like universal intelligence occurs at the beginning of the universe rather than the end, what one might call the Alpha Point. Even more speculatively, there are certain hypotheses that say the universe is cyclical, that a Big Crunch rebounds into a Big Bang. In this instance one universe’s Omega Point might be another universe’s Alpha Point; indeed, the next Big Bang might be deliberately induced or tampered with by the previous universe’s intelligence.
There is scientific speculation that black holes and their interiors could survive such an event intact to the other side. Assuming (and this is a big assumption) there is a way to escape, such as wormholes, intelligence could perpetuate itself. There is also the possibility of using black holes or wormholes to create “basement universes”. For all we know our Big Bang could be the result of one of these events. Although scientifically and philosophically this is pure speculation, more practically it could be a fruitful premise for science fiction.
Energy and Matter as frozen Thought
Perhaps even more speculatively, panpsychism holds that consciousness and thought cannot be explained by any emergent property of non-thinking non-aware matter, so thought, awareness, or something like it must exist apart from matter or energy. Consciousness in humans are thus an emergent property of particular patterns and structures of what we might call mind, psyche, psychic energy, just as the macroscopic objects we see have properties that emerge from the nature of fundamental particles of matter.
If we assume that mind is like matter and energy, then the fact that matter and energy are interchangeable and effectively merge at high energy levels becomes very intriguing. Matter could be conceived of as frozen energy, so by the same token it’s hardly inconceivable that energy in turn is frozen mind.
If this is true it suggests that mind, the stuff thought and consciousness is made of, could be converted to energy and matter at still higher energy levels, like that found at the Omega Point or at the Big Bang!
This also suggests a wilder possibility: that pure thought, or at least the psychic substance that thought is made of, may have been what filled the universe at the Big Bang and during at least part of the Planck era, before energy or matter existed. Energy and matter may both be manifestations or transformations of this original thought-substance.
A Thought-Dominated Cosmos: a long Name for God?
Some might identify this as one and the same with God or some other spiritual force, but there’s nothing supernatural about this idea. Then again, animism and spiritualism views spirits and even gods not as supernatural beings who sit above nature and its laws but rather as part of the fabric of the natural world we inhabit, arguably not qualifying as a religion as far as cultures dominated by Abrahamic concepts of religion are concerned.
You could say much the same for pantheism and especially pandeism, both of which are consistent with the idea the early universe was mind-dominated. Of course this idea doesn’t necessarily imply that the whole universe was one mind or even that there was any consciousness or thought involved (merely something that when properly assembled, like it is in human beings, produces thought), so you could take the concept in many different directions.
It seems that as we near the Alpha Point and the Omega Point not only the distinctions between physical forces but also the distinctions between science, philosophy, and religion break down and become one!
The Oneness of Science, Religion, and Philosophy
This shouldn’t really be a surprise, considering that science until relatively recently was outright called “natural philosophy”. What we call philosophy now back then was called “moral philosophy”. For whatever reason natural philosophers, i.e. scientists, have distanced themselves over time from the idea that they are even doing philosophy at all, adopting a pose of agnostic neutrality, but nevertheless the fundamental connection remains and at times makes itself evident.
Religion, too, is not as easily divorced from philosophy as it might seem. Much philosophy until relatively recently was explicitly founded upon religious and theological premises, and the influence of Greek philosophy upon the Abrahamic faiths, particularly mainstream Christianity, is well-known.
And this is in Western culture, where religion and philosophy are perhaps more divided than in any other major civilization, probably due to having been taken over by a non-Western religion (Christianity) in late antiquity. In Eastern cultures like China and India philosophy and religion aren’t so divided; famously, in these cultures it’s hard to tell where one ends and the other begins. Before Christianity Western culture was much the same.
Many Eastern religions accept schools of thought under their umbrella that don’t acknowledge the existence of gods or even the supernatural. It has been argued that we see the same phenomenon in the West, with Marxism (and more recently Intersectional Social Justice) allegedly being heretical forms of Protestant Christianity, but the difference is that Christians don’t accept such creeds under their umbrella. Not without reason of course: Marxism is atheistic, and Christianity without Christ is like Buddhism without Buddha, a logical impossibility that neither religion’s followers would or should accept. Still, it does make one think.
Conclusion
In any case the world is not as black and white between science, religion, and/or philosophy as it might appear at first glance, and the intersection of such ideas, especially as they concern the nature of reality, our existence, and the beginning and ending of the universe, provide tremendously fruitful ground for scientists, philosophers, thinkers, authors, worldbuilders, and other artists to explore.