The discovery of thousands of new planets outside our solar system (and the implication that there are likely billions of such planets and probably hundreds of billions more moons in our galaxy alone) has made the search for life infinitely more complicated. On the one hand, we developed better tools, which makes the search for life easier; on the other hand, we have many realistic possibilities to choose from. Physically possible does not equate to statistically probable. Where before we thought that the search for life would be akin to searching for a single tulip in a desert, we now see it is more like searching for an amoeba on the Moon. Even if forms of life are relatively common in our universe, their threshold of detection is still quite low.
Rather than regarding the overwhelming majority of planets and moons as failures unworthy of further study, we should instead recognise them for what they are: they’re not empty. In fact, a very high number of them might have been (and might yet be still) on the cusp of flourishing with life, if provided the specific potential to do so. What if a significant percentage of those planets and moons require only a few hundred kilogrammes of ‘the right chemical stuff’ to spark their own, unique biotic revolutions?
This is not panspermia, or even terraforming. Here I elaborate one of many possible applications of prebiotic chemistry, protospermia, which should be debated as a technologically viable human endeavour. If humans are capable of instigating multiple origins of life under a broader array of circumstances than life currently exists, ought we to do it?
Exoplanets have revolutionised astronomers’ understanding of planetary system processes, architectures and planet types. According to NASA, the Kepler space telescope detected more than 2,600 planets from outside our solar system. Many of them could be promising places for life. But Kepler has scanned only a tiny patch in the sky. Many multi-billion-dollar missions are currently in development that aim to detect signs of life as a key scientific objective. Designing next-generation missions of this magnitude requires some essential scientific steps. Scientists must evaluate how the physicochemical characteristics of various planets shape the emergence and evolution of life, determine planetary habitability, and how these characteristics affect potential signs of life and their detectability. Lots of targets and lots of possibilities.
The sky is vast, yet the large number of planets that could be one chemical step away from life might mean that the probability of detecting life could still be tens or hundreds of years away. As one example, even though planets seem habitable, moons might be needed for long-term orbital and climatic stability; large binary planet-moon systems like ours could be rare but essential for life’s sustainability over billions of years. As another example, the amount of exposed land might be a sensitive parameter for elemental availability, plate tectonics and climate regulation; there could be some ratio of water to rocky material that needs to be just right or the planet is drowned, desiccated or tectonically deadlocked.
The bounty of planets that astronomers have found is throwing sand into the gears of the search methods and criteria. Let’s assume we have a dozen planets and 100 moons per star, and we have about a billion suitable stars in the galaxy, and that it (optimistically) takes approximately one year of data collection to assess the habitability of each candidate. Let’s remain optimistic, and also assume that only 10 per cent of these objects would fall into a category of ‘habitable’ so we can focus only on those. It would still take billions of years to assess each of these targets. If we could narrow down the list of candidates at the outset using a set of first principles of biogenesis that could have generated life-as-we-know-it, say by a factor of one in a million or one in a billion, then the planets-and-stars search drops to a far more manageable number.
In the process of making the scale of searches more practical, we still have a daunting number of planets to search. The probability that most of them will not contain life is very high. Even then, scientists are working with fairly narrow presumptions about what that life even looks like in order to tune the search apparatus appropriately. Life that appears very different from how we understand it at present would be even harder to find.
We should just come out and say it: even in the optimistic scenario where life occurs relatively frequently in our galaxy, this doesn’t mean that we’ll detect it any time soon. Of course, we shouldn’t stop searching or surveying such planets. Life might be much more common than we currently estimate, or more obvious. We could also get lucky enough to find another life-bearing planet by chance. Or we might one day cleverly overcome current observational obstacles in some unforeseeable way.
Life-as-we-know-it is as much an expression of the conditions on our planet as it is of biological organisation
It’s important to see the full opportunity waiting ahead. Each planet or moon is its own world, with its own history and story to tell, and its own potential (however one might define this) for the future. Though mostly barren of life, they are far from empty; many are chock-full of the materials that would go into life-generating goo: sugars, amino acids, carboxylic acids and powerful molecules that drive reactions away from equilibrium. On bodies where widespread life might not be possible, many of them nevertheless contain microniches where life can take root and flourish for billions of years. Conceivably, for every planet that crossed the threshold of biogenesis, there were scores more that came part or even most of the way that just missed the nudge to do so.
Life is a molecular memory written in genes describing a basic chemical architecture. But life-as-we-know-it is as much an expression of the conditions on our planet as it is of biological organisation. DNA is at least a 4-billion-year-old encyclopaedia with information about the extant world, and the world that once was. Yet, setting aside the use of technology, DNA has only limited utility for worlds that differ markedly from our own.
Life’s encyclopaedia arose during an era in which a unique relationship between triples of nucleotides and single amino acids became locked in place. NASA’s Astrobiology Program funds studies of the origins of life, in part, to help guide the search for life beyond our solar system. Understanding what occurred during the era in which the relationship between life’s operatives and its basic chemical architecture became fixed is entirely worthwhile. Thousands of years ago, philosophers debated what Aristotle referred to as ‘the vital process of Earth’. More than a century ago, scientists began to peek into and describe the complicated chemical processes occurring inside living cells. Half a century ago, scientists learned from atmospheric chemistry how to synthesise some of the building blocks of life.
Building on these foundations, origin of life studies have, for decades, been guided by a paradigm set by the specific building blocks of Earth’s life. The ability to create life’s building blocks in the laboratory, such as the lipids, amino acids and nucleotides, led to an immense exploration and tabulation of abiotic chemical reactions that produce individual building block molecule types. Research taught that chemists can produce these molecules in the laboratory, but making them interact with each other in a lifelike way currently eludes us. What origins of life scientists are seeking now is to begin driving life’s behavioural chemical attributes, not just its components. What they seek is to make abiotic chemical systems behave as though they were alive.
The pursuit of solving the particular problem of the origins of life on Earth can help solve the more generic problem of understanding the origins of any life, anywhere, anytime. With such knowledge, it might be possible to eventually ‘fill in the gap’ between natural processes linking geochemistry and biogenicity on many different worlds. If astrobiologists could physicochemically assess what ingredients might enable many planets to generate their own forms of life that were ‘of’ that planet, it might bring forth life where and how it wouldn’t otherwise have existed. We would deliver a starting point, but the unfolding trajectory of this chemical system won’t be directed, it will be self-directed and self-organised. What occurs next will result from the coevolution between the chemical goo and the planetary body itself – a solution that is unrelated to our biology, and specific to that planetary system.
Sending the chemical capacity for life to emerge on another planetary body is what I call protospermia. This differs from terraforming, which involves altering an existing environment to make it suitable for a particular form of life. Finally, panspermia delivers one particular form of life to an existing environment such that it might or might not eventually take root on its own. These methods all involve relocating existing life forms to another planet, one way or another. Protospermia is different. It doesn’t require ploughing over whatever living or nonliving chemical systems were already present at the destination.
With protospermia, whatever arises after we provide a nudge toward biogenesis would be just as much a product of that environment as our life is of Earth. Whatever arises after we provide a nudge might (or might not) look anything like Earth life. It would be unique and ‘of’ that destination body as much as its rocks on the ground and the gasses in its atmosphere.
Writing in Terraforming (1995), the British physicist Martyn J Fogg said:
Terraforming is a process of planetary engineering, specifically directed at enhancing the capacity of an extraterrestrial planetary environment to support life. The ultimate in terraforming would be to create an uncontained planetary biosphere emulating all the functions of the biosphere of the Earth – one that would be fully habitable for human beings.
Scholars have debated the ethics of directed efforts at terraforming for at least a few decades. There is no consensus but a spectrum of viewpoints ranging from ‘We must prioritise the preservation of Earth life as a unique phenomenon’ on one end, to ‘We must protect and preserve any possible alternative life that could be found elsewhere’ on the other. A minor offshoot of the second perspective includes preserving the ‘aesthetics’ of places that are unlike Earth, akin to an interplanetary National Parks system.
Ethical debates about terraforming have begun to assume a pressing moral importance in recent years. For instance, Mars is nearly habitable, it’s within reach, and thus many scientists and others have debated terraforming options: from preserving and appreciating the beauty of Martian landscapes as they are and avoiding ‘terraformed images’ (the approach favoured by the astrobiologist Sean McMahon and the philosopher Robert Sparrow) to questions about the moral permissibility (raised by the philosopher James Schwartz) and environmental ethics (discussed by the NASA scientist Christopher McKay and the philosopher Eugene Hargrove).
Scientists and engineers are now exercising an ability to permanently reconfigure (and disfigure) the Earth, while also significantly reducing the technological barriers of extraterrestrial transportation. Destinations in our galaxy that once seemed ‘impossible to reach’ are now just ‘prohibitively expensive’. These destinations are, as I write, moving quickly into an even lesser category of ‘logistically difficult’. Various agencies and groups including NASA, the European Space Agency (ESA), the Committee on Space Research (COSPAR), the United Nations Committee on the Peaceful Uses of Outer Space (COPUOS), and the UN Office for Outer Space Affairs (UN OOSA) all maintain standing offices and observe international agreements regarding forward and backward contamination of places within our solar system. A private nongovernmental organisation is seriously funding an effort to send interstellar beacons to directly image a nearby planetary system. This is real. What once was an exercise in international ethics, scientific reservation and esoteric theology might soon exhibit competitive legal, economic and political dimensions that reshape the collective future of our species.
It’s an effective shrug of the shoulders regarding the effects of turning rocks into organic casino parlours
Protospermia, as a technological capability, could defy ethical resolution according to the criteria explored in previous debates. First, the timescales involved aren’t inherently human, or at least human-cultural. If we choose to ‘send the goo’ to various destinations in our solar system and beyond, it would likely take thousands or millions of years for a self-replicating chemical system to emerge, far beyond even the most long-lived of our mortal concerns. Second, by sending a biogenic capacity and not a strictly predetermined molecular architecture, we would circumvent some of the uglier, more domineering aspects involved with pushing an alien (ie, Terran) physiology on other unsuspecting worlds through in situ missions or terraforming. Whatever arose would be a product of that world. If that world already had life, it is very unlikely that the goo we send could practically overwrite what is already there.
Third, and perhaps most importantly, protospermia challenges humans to articulate our core motivations and values regarding the importance of ‘life in the Universe’. One might argue that life and lifelike systems are a special, maybe even unique, expression of the universal capacity of chemistry. It doesn’t occur everywhere at all times, as its less specific ancestor covalent chemistry does. Our ability to imagine and quantify these differences is, itself, an indicator of the imaginative possibilities of universal chemistry. One might therefore also make an aesthetic argument that increasing a body’s chemical novelty (ie, generating life unlike our own that is derived from that body) has a more positive aesthetic result than keeping a body in its present condition. This in effect extends the argument that various forms of life have intrinsic aesthetic value, not just their source environments.
On the other hand, one might also make a principled argument for something akin to Star Trek’s Prime Directive: it is simply unacceptable (or at least, not desirable) to meddle in the internal affairs of other places and planets. Look but don’t touch. There is also no certain knowledge that life might not one day originate in these places without our intervention. This perspective has merit, particularly in the sense that it is an effective prophylactic against the law of unintended consequences. It is impossible to negatively affect what we have chosen to not study directly or physically disturb.
As in the Star Trek universe, the tension between the value of abstract knowledge and the necessity to interact with (and potentially disrupt) a system to obtain that knowledge is where the meaningful moral and ethical argument begins, not where it ends. It gets complicated very quickly. A generalised policy of principled prophylaxis is also a policy of sanctioned ignorance that could severely hinder understanding of how the Universe functions and where life, as a general phenomenon, arose and might occur. A generalised policy of implemented protospermia in the name of chemical aesthetics is also a policy of tremendous matter redistribution (life, once it’s taken hold, tends to follow its own organisational priorities), and an effective shrug of the shoulders regarding the effects of turning rocky bodies into organic casino parlours. Strong moral and ethical arguments can be made for and against both courses of action.
Whether we are creating new forms of life in a lab on Earth or elsewhere in the Universe – we are currently creating new chemical possibilities, and therefore new potential forms of appreciation and value that can affect the way we live. The technological possibilities of applied prebiotic chemistry are only now beginning to be resolved. We can imagine using chemical reactions to perform computational processes much more efficiently than silicon chips. We can imagine self-organising organic chemical systems engineering solutions to pressing environmental problems. We can imagine hybrid systems composed of Earth life and prebiotic chemical systems greatly expanding and stabilising human exploration of the solar system.
The origins and evolution of Earth life have always been proximal to these anxieties in human culture, and the additional capability of selectively instigating new forms of life has an equal potential to alter our perceptions of self. We experimented wantonly, and without much regard for consequences on Earth itself. The real tension, moving forward, derives from our own uncertainty about who we are now, what we wish to become in the future, and what we might unknowingly risk becoming in the process. We need to take a more educated approach in the future, both here on Earth and anywhere else in the Universe that we go, or send the goo.