Did “The Seeds Of Life” Originate In Outer Space? Welcome To The Wild Theory Of Panspermia

Perhaps life did spring into life spontaneously due to the act of some “creator”, but people of science, so he argued, should not seek supernatural explanations if “a probable solution, consistent with the ordinary course of nature, can be found”. So, what then could explain the appearance of life on an early chaotic and wholly hostile planet? Well, the speaker had some ideas on this.  

“When a volcanic island springs up from the sea, and after a few years is found clothed with vegetation, we do not hesitate to assume that seed has been wafted to it through the air, or floated to it on rafts”, he explained. So, if this is possible for explaining the transmission of life across the planet, presumably from an area rich in life to one that is poorer, why can’t the same idea work for the Earth more generally?

“Is it not possible, and if possible, is it not probable, that the beginning of vegetable life on the Earth is to be similarly explained? Every year thousands, probably millions, of fragments of solid matter fall upon the Earth – whence came these fragments?”

The answer to the origins of life, so the BAAS members were told, may not be found on the planet itself, but may have come from outer space. That some distant planet harboring life may have experienced a devastating collision with some other object, which in turn threw thousands of chunks of its own surface into space that traveled through the void for countless years before eventually crashing into our fertile but hitherto unpopulated planet. If any of these falling “stones” was covered with sufficient amounts of “vegetation”, the speaker said, then it could have spread that vegetation like a seed being planted in good soil.

“The hypothesis that [some] life [has actually] originated on this Earth through moss-grown fragments from the ruins of another world may seem wild and visionary; all I maintain is that it is not unscientific, [and cannot rightly be said to be improbable.]”

This idea, now understood as “Panspermia” (“pan” and “sperma” meaning “all” and “seed” in Greek), that life on Earth originated somewhere else in the universe and was transported here by some unknown means, is now relatively well known among scientists and the public alike. But it is not a new idea. In fact, Thomson, otherwise known as Lord Kelvin, gave this address to the BAAS in 1871, 154 years ago. The term “Panspermia” itself was coined by the ancient Greek philosopher, Anaxagoras (500–428 BCE), who speculated that the seeds of life could be present throughout the universe.

Today, the theory of Panspermia has become part of the modern scientific landscape, albeit a contentious one, receiving increasing attention from scientists attempting to figure out how life may have started and how it could have spread throughout the cosmos. Even the late Stephen Hawking raised the possibility of Panspermia when he stated that “Life could spread from planet to planet or from stellar system to stellar system, carried on meteors”, in his 2008 “Why We Should Go Into Space” talk as part of NASA’s 50^th Anniversary lecture series.

But is this just a hypothetical idea or is there any reality behind it? The scientific community, it seems, is divided on the subject, but it is nevertheless inspiring debate and further exploration.  

Life here or there?

Panspermia effectively combines two questions that have preoccupied humans for generations: where did life come from and is there more elsewhere in the universe? As my colleague Alfredo Carpineti stated in 2020, the answer to both these questions may be one and the same. But before we go into the current state of research into this idea, we need to understand why some people might think the answer to the origins of life isn’t satisfied with what we have here on Earth.

Contrary to the views that life came from elsewhere, the idea of abiogenesis states that it actually emerged on Earth, naturally forming from non-living chemical compounds. In this context, aspects and components of the early planet – such as water, volcanic activity, and various gases like methane, ammonia, and hydrogen – laid the groundwork for simple organic molecules, such as amino acids and nucleotides, to form. As time progressed, these molecules began to self-organize into increasingly complex structures, culminating in self-replicating molecules and the first cells.

This idea was first popularized in 1953, after the famous Miller-Urey experiment showed how amino acids could form in the laboratory when the conditions of the early Earth were simulated using a mixture of simple gases, small organic molecules, and a little electricity. Since then, scientists have continued to experiment with ways to understand how inorganic molecules and other non-living compounds began to form the first stages of life on the planet. This includes how rain may have helped form the first cells, prompting life into existence by offering RNA – possibly the earliest form of self-replicating genetic material – a membrane for stable material transfer.

But while abiogenesis remains the mainstream explanation for how life started on Earth, it has some important limitations. For instance, even the simplest forms of life are exceptionally complex, so it is challenging to explain the formation and assembly of its principle components under prebiotic conditions, and moreover, how this can then be transferred to a system capable of Darwinian evolution. To put it another way, to date no mechanism has been defined for the active selection that allows molecular evolution and abiogenesis to create the “fitness” we understand for biological organisms more generally.

The case for Panspermia 

So, what about Panspermia? How might this help address the gaps? Well, there are currently a few models of Panspermia. The first is radiopanspermia, which suggests bacteria or other microorganisms such as spores could have been pushed through space by radiation pressure produced by stars. Once any of these organisms landed on Earth, they were then able to grow and evolve into more complex life forms over time. This particular idea was posited in the early 20^th century but is less popular among proponents of Panspermia these days.

Instead, current ideas about microbes from outer space tend to be more in keeping with the rock’s-flung-into-space hypothesis suggested by Lord Kelvin, as mentioned above. In this version, known as lithopanspermia, microorganisms could survive the harshness of space if they could somehow hitch a ride on asteroids, planetoids, or comets that protect them from the harsh conditions involved in interplanetary or interstellar travel. If a microbe was sufficiently snuggled up in the surrounding rock, so the idea goes, it could be shielded from cosmic radiation and the intense heat produced when the meteor entered a planet’s atmosphere.

Past research has suggested that microbes could indeed survive the three stages involved in this explanation – ejection from a planet, transit through space, and eventual re-entry – as long as they are insulted in something. Having said that, less is known about the final stage here, as the impact on a new planet includes various unknowns that are difficult to model. For instance, the heat produced by friction as the microorganism’s rock enters the atmosphere could produce a fusion crust consisting of the meteorite’s outer layer that melts and erodes. Nevertheless, scientists have so far shown that the principles for cosmic travel and transference of microbes between planets are feasible.

In addition to these ideas, there is also the possibility of what is referred to as directed Panspermia. Anyone who’s a fan of the Alien films and Prometheus may be able to anticipate what this one involves. Rather than necessarily being the outcome of chance, whereby the seeds of life arrive on a planet, say Earth, by accident, there is always the possibility that intelligent extra-terrestrial life brought it here deliberately or unknowingly. In this version of the hypothesis, life on Earth is actually alien life that has just been here a really long time; its origins coming from somewhere else altogether because of some other unknown advanced civilization that either deposited it on our young planet or accidentally contaminated it while visiting.

While this may be difficult to swallow for some, the concept of directed Panspermia may be relevant to future human activities in outer space. The next generations of space explorers could themselves transport terrestrial microorganisms to other planets, thereby seeding them with the basic ingredients for life. This raises various questions and sticky dilemmas, as it is not clear whether such an outcome is a good or bad thing, whether the spread of terrestrial life to other planets will interfere with other lifeforms if they exist (literally becoming an invasive alien species), and whether we can be consciously and ethically responsible for increasing suffering in the universe. I guess, in the very least, this line of enquiry opens up relevant philosophical issue for consideration.

But does any of this matter?

As our space technologies and exploration ambitions continue to develop, it may become possible to add weight to the various ideas associated with Panspermia. However, at present, there is little empirical evidence to back any of it up. Space’s harshness cannot be underestimated. The experiments where bacteria have been placed outside the International Space Station have shown that these organisms suffered considerably when exposed to space for even just a year. As New Scientist has pointed out, this still provides a window for space travel, but it is a short one and it makes Hawking’s idea of interstellar transfer look pretty unlikely (if not impossible).   

But even if Panspermia did cause or contribute to early life on this planet, what does it ultimately offer us? Instead of answering how life originated, it merely transfers the question to other, more distant places. We’re no closer to addressing that ever-present problem. Still, the future of space travel may well offer us more insights into these questions, and if they can bolster the Panspermia hypothesis then we are likely to have many more intriguing questions ahead of us beyond how it all started.