Once upon a time, discussion of the possibility of alien life was the province of people with some really weird, unscientific ideas. Then along came astrobiology. Since it was formalized in 1998, NASA’s astrobiology program has sought to answer three broad questions:
Q1: How does life begin?
Q2: Where does life exist elsewhere in the universe?
Q3: What is life’s future on Earth and beyond?
Of course, in some sense this is nothing new, as people have probably been speculating about what was “out there” and whether we are in fact alone in the universe since the invention of language. What has changed in recent years is that these questions have become accessible to serious scientific investigation. Progress in astrobiology has been nothing short of explosive: in 1988 we discovered the very first planet beyond our own solar system, but to date we have catalogued nearly 4,000 planets in roughly 3,000 different star systems. In 2016, scientists discovered a potentially habitable, earth-size planet in the system closest to us (Proxima Centauri, just 4.2 light years away) and early last year, a treasure trove of 7 terrestrial, temperate planets was found in the Trappist system only 40 light years away, 3 of which are within the habitable zone. The flood of discoveries has been so fast and furious that the checkers can’t keep up, so thousands more possible planets await confirmation. And we have not seen anything yet – as new instruments like the James Webb Space Telescope come online in the next few years, astrobiologists will be presented with a veritable avalanche of data.
But why, if you are not an amateur astronomer, should you care? Because these discoveries shed light on one of the most significant questions humans have ever pondered: are we alone in the universe? Although it is fair to say we still have not solved the question of precisely how life evolved on Earth, biologists are rightly confident that living systems evolved from chemical ones. This doesn’t happen every time there’s a puddle on a planetary surface, of course, so we have to think probabilistically: the more planets there are, the more different chemical systems will form, and the more chemical systems form, the greater the chances that some of them will develop into life – perhaps life gazing up at our Sol in their night sky and pondering the same questions we do.
It would be nice if we could be more precise about what the probabilities are like, rather than simply saying, “Lots of planets means good chances of life somewhere”. The famous astronomer Frank Drake thought about this problem and formulated his classic Drake equation back in 1961. The equation lays out the basic variables involved in the origin of life and then attempts to estimate each to give us a ballpark idea of the probability that there is in fact alien life out there. Not surprisingly, there are many variations on the original equation and debates over the values of many of the variables, but the universe is so mind-bogglingly vast that it’s actually quite difficult to make the equation predict only a small number of life origins. Not only that, but our ability to estimate these values accurately is rapidly increasing. Twenty years ago, for example, we could only guess at the ratio of planets to stars, since we could see the latter though our telescopes but not the former. Now the exoplanet data shows there is roughly one detectable planet per star, and the true number of planets is almost certainly higher. But if we accept 1:1 as a reasonable lower bound on the ratio, then there are something like 1,000,000,000,000,000,000,000,000 tickets for life’s lottery floating around the universe. While people often say the odds of life spontaneously occurring is a miracle, a single isolated origin of life in the 14-billion-year history of such an immense universe would be a miracle of another sort.
The synergy between long standing theoretical arguments for extra-terrestrial life, the flood of new data concerning the abundance of exoplanets, and our increasing confidence that many places within our own solar system have all the ingredients needed for life helps explain why NASA’s chief scientist, Ellen Stofan, predicted recently that we will probably find evidence of life beyond Earth within the next 20 years – that’s during the life of even some of our more seasoned readers! One might think that, with such a momentous event right around the corner – a discovery which will transform the way we see ourselves, our future, and our overall place in the universe even more profoundly than Darwin’s modest revelation – there would be an enormous number of experts from all corners of academia thinking through its various implications. That has yet to happen, mainly because astrobiology’s change in status has been so rapid that most academics have yet to notice the historic challenge rushing towards them. Of course, we are not certain we will find life beyond Earth and, if we do, we have very little idea as to what it will be like. But what we do know for sure is that whatever we find will be truly momentous – and that is just as true if our search ultimately proves fruitless, as it is if we find intelligent aliens in the next system over. Thinking deeply and systematically about these broader implications must involve experts outside the sciences, including philosophers, theologians, historians, literary scholars, and many others – which is why I am currently working with a team of colleagues to found a new, highly interdisciplinary academic society, SoCIA (Social and Conceptual Issues in Astrobiology).
Social and Conceptual Issues in Astrobiology?
One of the first orders of business for our new group will be to survey this new intellectual terrain and determine precisely what the most pressing questions are. Since I am mostly a philosopher, in what follows I will limit myself to a brief overview of some of the more obvious issues of interest to philosophers (who, so far anyway, constitute a clear plurality of the non-scientists involved).
Few of the philosophical issues in astrobiology are entirely new, of course, since philosophers have prided themselves on thinking about weird things for thousands of years. However, philosophy of astrobiology is not simply old wine in new bottles. The fact of the matter is that adopting a truly astrobiological perspective – taking quite seriously the possibility that the universe is teeming with life (in particular, intelligent life) – changes old debates in important ways. To take just one example, arguing that rational beings have a higher moral value has long been equated with anthropocentrism, but this only makes sense if we assume that the only rational beings under discussion are human. To paraphrase the church lady, it’s suspiciously “conveeeenient” to conclude that the salient moral feature just so happens to be one only humans possess. However, from a thoroughly astrobiological perspective, it’s hard to argue that reason is even uncommon in the universe, much less unique to some hairless apes on a single insignificant planet. Indeed, it’s entirely possible there are beings intellectually superior to humans. In that case, someone who views reason as central to moral value might well grant that they are also morally superior to us and, whatever else you might say about such a position, it is clearly not anthropocentric.
Another example where the astrobiological context can alter the nature of the philosophical debate, in practice if not in principle, is in environmental ethics. Thus, while it is certainly possible to argue that antelopes or mountain ranges have moral standing intrinsically and irrespective of the impact they have on humans, it’s very difficult to disentangle the intrinsic value we find in such entities from their instrumental value. On Earth, we all are intimately interconnected by an ecosystem that has coevolved over many millennia. Thus, there are excellent, perfectly self-interested, reasons to be a tree hugger, since tinkering with our shared ecosystem in any significant way is dangerous to us all. Surely a (large) part of what motivates the average environmentalist, whatever they may say about the intrinsic value of all life, are such practical concerns. But these vanish entirely when we are talking about life on another planet, since there is no meaningful way in which what happens to that life will impact the terrestrial ecosystem (unless we make some very surprising discoveries indeed). I suspect even the deepest of deep ecologists would, if pushed, prefer to mine the slopes of Olympus Mons on Mars for some resource critical to human survival than those of Mt Rainier. Bringing environmentalism into the context of astrobiology thus lays bare an unappreciated, even explicitly denied, element of its support.
Of course, there are also issues central to the philosophy of astrobiology that are not really new at all. Philosophers and biologists have debated the nature of life since before these existed as distinct disciplines. But the nature of life has long been a highly abstract question attracting little serious attention: how else can we explain the fact that virtually every biology textbook “defines” life by simply listing a number of characteristics shared amongst life on Earth? Even the ancient Greeks knew this was an unacceptable way to construct a definition, but since ancient times there has been no real pressure to change. However, once imminent scientists and engineers began struggling to create life in the lab and design experiments to detect alien life on other planets, the question could no longer be sidestepped.
Not surprisingly, there are nearly as many answers to this question as there are philosophers considering it. It’s useful to think of the various options as being arranged on a “pragmatic continuum” of sorts. On one end are those who don’t want weird, abstract definitional discussions to get in the way of the science. Depending on how strongly one embraces this attitude, it can lead to a number of different positions. Perhaps we shouldn’t worry about defining life at all now, instead trusting that this will become more clear once we have learned more about biology in the broader universe. Or maybe we should just pick a couple of very general biological attributes that we can easily test for remotely and make them into a provisional definition with the hope that they prove conveniently universal. Then in the middle of the continuum are those who accept that we need to define life, but argue that no single definition is either necessary or satisfactory. And of course, on the other end of the continuum there are always those fully convinced that their definition is the only true one. Thus, biologists tend to want a definition that preserves the traditional boundaries of their discipline and vindicates their historic focus. Chemists tend to emphasise the necessary characteristics of the chemical systems they believe led to life in the primordial oceans. And the physicists defend a conception of life as just another type of interesting physical system – specifically, the sort with the ability to defy entropy under certain conditions.
Finally, there are obvious applied ethics questions, which boil down to different variations of the question, “If there is life on other planets, what exactly are our obligations to it?” Again we see a continuum, with some thinking we have a new kind of manifest destiny to explore space and harvest its resources, and thus not worrying overmuch about the fate of alien bunnies, much less microbes. Others take a diametrically opposed view, arguing that, if we find life beyond Earth, it must remain entirely untouched. As Carl Sagan put it; “If there is life on Mars, I believe we should do nothing with Mars. Mars then belongs to the Martians, even if the Martians are only microbes.”
At the moment, planetary protection policies take a middle position, acknowledging the value of alien life and our responsibility to structure missions in such a way as to protect it. However, the protection of alien life is viewed as being largely for the purposes of preserving the science such life makes possible and thus is ultimately instrumental in nature. It is only a matter of time before we are forced to choose the basis for our moral valuations more precisely. Consider that some of the most promising places to look for life in our own solar system are in the oceans lying beneath the ice sheets of several of the moons in the outer solar system. Europa, for example, is thought to possess a warm, salty ocean beneath several kilometres of surface ice – likely an ideal place for life to evolve. So there could well be a complex ecosystem in the Europan ocean – not just microbes, but alien multicellular life of great diversity and abundance. The problem is that we will only be able to find out about the Europan ocean by penetrating the ice sheet covering it, and any such penetration will inevitably mean contamination by terrestrial microbes. In other words, we are likely to face a dilemma where we must choose either to study an amazing example of alien life at our doorstep while risking its destruction or protect that life by resigning ourselves to ignorance.
An Invitation
The issues I touch on here are just the tip of a very large iceberg and any graduate student worth her salt could come up with a dozen more over a few beers. News stories that raise these questions are a dime a dozen. For example, the privately funded Interstellar Beacon Project recently announced it will soon begin to beam the contents of Wikipedia to all nearby star systems that might harbour alien life. Is it acceptable to allow a single individual to make this decision on behalf of humanity? If not, who should decide and how? If we do want to make contact with aliens, what should we say? We are also beginning to think seriously about human colonies in space, but how should these be set up? Should they be the province of their founding countries and obey those countries’ laws, as happens now on the international space station, or should we found them collectively and develop a new kind of space law to run them? What sorts of governments should we allow to run these colonies – it could be that democracies are not well suited to the harsh conditions of an early colony, for instance.
We need a diverse group of the best the brightest to help address these challenging questions. If you are an expert who feels you can contribute, please consider joining SoCIA – our second conference will be in Reno this March, and planning is already underway for a third and fourth conference to follow.
