(ORDO NEWS) — Panspermia is the idea that life exists throughout the universe and originates on new planets through comets, meteors, and other interstellar travellers.
Readers of Wikipedia can see that this idea is labeled as a “side” theory. But is it? Or is panspermia as likely as the idea that life on Earth arose from a soup of chemicals, lightning strikes and heat, as the most widely accepted theory of the origin of life on our planet says?
The current theory is that a brew of primordial chemicals was struck by lightning, boiled with heat, and turned into an organism capable of replication. This first step towards viable organisms capable of replication is probably the most difficult step any life must take.
Interestingly, despite all its achievements, modern science has never been able to repeat this development, with the exception of a few promising chemical components.
Since this first step is so difficult and unlikely, is it possible that it only happened a few times during the development of our Universe, and these few manifestations of life were transported through space to “seed” the Universe with life.
At some point, this topic became what I wanted to study in my scientific career. Together with a physics professor who had a device that could create an ultra-low vacuum (to the point where molecules seeping through three inches of stainless steel were a source of contamination), I decided to look into the matter.
The idea was to take microorganisms, spores and other life forms and see if they could survive in the vacuum of space; this would, in fact, show that panspermia is possible.
Why didn’t we do it? Because it’s already been done. Since the heyday of the early space program, NASA has funded just such studies and found what we initially expected: panspermia is possible.
Origins of the controversial theory
The theory of panspermia can hardly be called new. It is known that philosophers as early as 500 BC claimed that life exists throughout the universe. Over a century ago, the Swedish physicist and chemist Svants Arrhenius was probably one of the earliest modern scientists to postulate the possibility of panspermia.
Arrhenius believed that spores could have traveled through the vacuum of space and brought life to the universe, although of course this was impossible to verify at the time.
More recently, two different versions of how panspermia can occur have been put forward: “soft” panspermia, when amino acids and nucleic acids are transferred through the universe, and “hard” panspermia, when real spores and organisms are seeded, and not just the building blocks of life.
Another theory of “hard” panspermia is that instead of traveling through interstellar space, life could have formed on one of the early planets in our solar system and, as a result of collisions with meteors and asteroids, was transported from one planet to another by cosmic ejecta.
But what is the evidence for this theory? Can life survive in outer space? Scientists admit that it would be difficult for mammals like us to survive there alone; our lungs would burst in the vacuum of space, and we would find it hard to endure ultraviolet radiation and extreme cold. The question comes down to what type of life could survive.
In order for panspermia to function, a viable organism must escape the atmosphere and gravitational
one planet, travel through space and survive after returning through the atmosphere to another planet. Each of these stages has been explored and there are viable routes for each of them. In fact, an “escape” scenario might not even require things like a meteorite fall.
Aboard the International Space Station (ISS), viable microbes and spores have been detected in low Earth orbit. It seems that the key factor is not the ability to survive in the cool vacuum of space, but protection from ultraviolet radiation, which quickly destroys nucleic acids when exposed to it, even inside the cell.
Possible forms of UV protection can be found in meteorites, or even in soil, where a rough surface allows the creation of spaces shielded from radiation.
Paths through space
As far as viable pathways for panspermia are concerned, methods of travel through space have also been studied (which was an area I previously had a professional interest in). In 1985, a paper was published in the journal Nature showing that panspermia was possible in simulated space, albeit with the limitations discussed above.
In fact, cooler temperatures helped stabilize the spores. Later this was studied in space, and not only with the help of simulations. In one study, Bacillus subtilis spores survived in space for six years when they were protected from ultraviolet radiation by mixing the spores with soil-like materials on the PERSEUS mission.
This may seem rather overwhelming, but if you look at the persistence of spores in the harsh environment here on Earth, then perhaps this is not the case. The spores are extremely hardy and can withstand high doses of radiation, cold and ultraviolet light; at least when compared to their live counterparts.
But no matter how tenacious they are, can spores survive after entering the planet’s atmosphere? As it turns out, yes they can.
In “Survival of Bacteria and Spores under Extreme Impact Pressure”, published in 2004 in Monthly Notices of the Royal Astronomical Society, researchers M.J. Burchell, J.R. Mann, A.V.
Bunch found that when spores and living bacterial cells are subjected to shocks equivalent to those they would experience when entering the atmosphere and hitting the planet, although they do not feel particularly well, their survival rate is finite and, as it turns out, at least sufficient for the origin of life.
In addition, they can survive high re-entry temperatures as only the leading outer parts of meteors and asteroids are exposed to extreme heat during such re-entries.
But do interplanetary/interstellar objects make it to Earth? The short answer is yes: rocks have been found on Earth that have been proven to have formed on Mars. More recently, an unusual interstellar object ‘Oumuamua has been discovered; although this mysterious object was very large, nothing rules out the possibility that much smaller objects could pass through interstellar space much more often than we think.
Given that panspermia is certainly a real possibility, what are the immediate consequences? First, it would be surprising if Mars and Earth did not have a common biological background.
Our relatively close proximity and the knowledge that we have exchanged objects in the past may mean that the discovery of life on Mars – both in the past and in the present – should be a reasonable expectation. But the absence of life (or at least a history of life in the past) on Mars may be more surprising.
We also know that life can survive in space. Does this mean that we should expect that methane, or predominantly biological gases found on other planets, will be considered biological until proven otherwise?
In conclusion, we know from our studies of life on Earth that it is hardy and can survive in almost any extreme environment on our planet. In this regard, the question arises: why the same cannot be said if suitable conditions are created in space?
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