Earth is a planet that exhibits an immense biomass and an incredible biodiversity. Yet, the question arises as to whether the diversity as observed on Earth reflects the limits of life or whether life elsewhere in the universe could manifest an even greater diversity. To examine the question further, I review some of the limits of life as observed on Earth and then ask what specific adaptation mechanisms could reasonably occur on other planets and moons to extend the limits of life to environmental conditions usually not found on our planet. As we currently do not have any convincing evidence for the existence of extraterrestrial life, these extensions must remain in the field of scientific speculation. Yet, given the enormous creativity and flexibility exhibited by the organisms we know from our planet, it would be odd if life could not adapt to some of the conditions exhibited on other planets. Thus, my conjecture is that life in the universe would exhibit a much larger variety of forms and functions than life on Earth.

The landscape of life provides important basic information when preparing for the discovery of extraterrestrial life. We are familiar with life on Earth, but life might be so strange on another world that we might not recognize it; especially since there is not even a commonly accepted definition of what life actually is. Thus, it is important to be not too constrained and Earth-centric if we do not want to take the risk to miss it even if an organism is in plain sight. This applies to all life, from microbial to more complex, and also to signals from technologically advanced civilizations. Thus, open-mindedness for this quest is an imperative.

The range of life on Earth

The conditions under which life can persist are incredibly broad; however, the range under which life can originate is likely to be much smaller. Since the origin of life is an unsolved puzzle, I will focus on the persistence of life, particularly under which environmental stresses life exists on Earth. The life most familiar to us, consisting of organisms that live at conditions similar to those we are accustomed to, is generally referred to as mesophilic life. However, during the evolution of life, organisms, particularly microorganisms, conquered nearly all available environmental niches on and within our planetary crust.

Introduction

Over the past several decades sporadic attention has been given to the impact of discovering life beyond Earth, beginning with NASA's “Cultural Aspects of SETI” workshops in the early 1990s and extending to meetings sponsored by institutions as diverse as the Templeton Foundation, the Foundation for the Future, the American Association for the Advancement of Science, and the Royal Society of London (see Dick 2012, p. 917, for an overview and references). These meetings only partially dealt with practical steps to prepare for such a discovery. Here we enter the policy arena, and not just in a theoretical way. During Congressional hearings on astrobiology held in 2013 and 2014, members of Congress wanted to know “What should we do if life is found beyond Earth”? (US Congress 2013 and 2014). This is a policy question with no agreed-upon answers at this time. Discussions such as those found throughout this volume are essential background to decisions that will inevitably have to be made in the event of discovery. This section continues that discussion, but also attempts to tackle policy problems more directly, both from the point of view of approaches and practical steps.

If we are going to discuss policy at the interface of astrobiology and society, it would seem prudent to ask what lessons can be learned from the approaches, issues, and answers provided in previous endeavors such as the Human Genome Project, or in biology and society programs that exist at several universities around the world. In the opening chapter of this section, historian of science Jane Maienschein gives us the benefit of her experience as the long-time Director of the Biology and Society program at Arizona State University. She systematically lays out the issues and urges humanistic approaches to astrobiology. An important lesson learned is that scholars from the humanities, social sciences, and other areas cannot isolate themselves in their discussions and recommendations, but must interact in a meaningful way with both scientists and policy makers. Otherwise social science deliberations will remain an academic exercise divorced from political and scientific reality. Indeed, interactions across the sciences and social sciences in the astrobiological context bid fair to serve as a leading edge of what Harvard biologist E. O. Wilson has called consilience, the unity of knowledge across the humanities, social sciences, and natural sciences (Wilson 1998; Finney 2000).

When scientists, philosophers, theologians, and others think about extraterrestrial life, a fundamental roadblock is that the nature of such life is a matter of human imagination. Lack of data beyond Earth limits our capacity to think about extraterrestrial life, even if that capacity is being increasingly stretched by the discovery and study of extremophiles on our planet and exoplanets around other stars. Despite our growing ability to imagine previously unimaginable forms of life, when we think about extraterrestrial life, intelligent or otherwise, Earth remains our only example. And when it comes to thinking about extraterrestrial intelligence, this presents several very significant limitations, since it is quite difficult to imagine what we might share with beings that evolved on a world different from our own (DeVito 2014, 2).

First, the Earth-bound nature of the data on life we have predisposes us to think about extraterrestrial intelligence in human terms. When we talk about alien beings, cultures, or civilizations, it is difficult to move beyond what we know – imagination does not happen in a vacuum; it is based upon our observations of the world around us and the only observations of life, intelligence, and civilization we have are right here on Earth. Second, when we do attempt to think about extraterrestrial intelligence, there is a tendency to ignore the fact that we are building our ideas on comparison with our own world, and often that comparative structure is not grounded in a nuanced and complex understanding of our world and the history and nature of culture and civilization on Earth. Indeed, ideas like culture and civilization need to be problematized when we think about our own world, which makes this doubly important when thinking about what intelligent life might be like on other worlds.

There are two questions I want to explore in this chapter. First, I am interested in how notions of progress and development shape the imaginations of scientists and others when thinking about extraterrestrial intelligence (ETI), particularly when we are contemplating the moral nature of that intelligence.

Introduction: astrobiology and intelligence

The question of how intelligence evolves on different planets is a subject of fervent interest in many scientific and public domains. Yet, it has received little, if any, serious scientific attention in astrobiology. Astrobiology relies on an elegant paradigm: Earth as a natural laboratory. It seeks to investigate how life arose and evolved on this planet and to apply that knowledge to detecting and understanding extraterrestrial life. Thus, the study of the evolution of intelligence fits squarely within the field of astrobiology. But, despite a wealth of accessible data from “mainstream” fields, astrobiology has limited itself to studying the origin and evolution of early life and has not made the connection between these basic processes and intelligence. Why, in its 50-year history, has there been essentially no empirical work within astrobiology on intelligence?

What is intelligence?

Intelligence is, by nature, a fuzzy concept. That is, there are no strict boundaries on it and there is no scientific consensus on its definition (Sternberg 2000). The study of intelligence, therefore, necessitates a strong reliance on “bottom-up” empirical descriptions of a range of phenomena rather than a “top-down” hunt for a precise exemplar. Intelligence is not a binary trait. Rather, it is a multidimensional phenomenon which expresses itself in varying phenotypes and levels of complexity and is interconnected with the entire psychological make-up of any animal. Nevertheless, if we wish to use a working definition of intelligence, then we can refer to intelligence as a level of cognitive complexity, i.e. how an individual acquires, processes, stores, analyzes, and acts upon information and circumstances.

Despite its complexities and fluid boundaries, the phenomenon of intelligence is amenable to empirical scientific investigation just as any other biological property. The absence of the study of intelligence from astrobiology is due to a complex set of historical and psychological roadblocks. One of these may be the mistaken assumption that intelligence is not scientifically tractable. But foremost of these is our species’ adherence to the wrong model of life on Earth, one that promotes misconceptions that impede the way forward in the scientific study of intelligence in astrobiology.

How would intelligent aliens think? Would they have conscious experiences? Would it feel a certain way to be an alien? It is easy to dismiss these questions as too speculative, since we haven't encountered aliens, at least as far as we know. And in conceiving of alien minds we do so from within – from inside the vantage point of the sensory experiences and thinking patterns characteristic of our species. At best, we anthropomorphize; at worst, we risk stupendous failures of the imagination.

Still, ignoring these questions could be a grave mistake. Some proponents of the search for extraterrestrial intelligence (SETI) estimate that we will encounter alien intelligence within the next several decades. Even if you hold a more conservative estimate – say, that the chance of encountering alien intelligence in the next 50 years is 5 percent – the stakes for our species are high. Knowing that we are not alone in the universe would be a profound realization, and contact with an alien civilization could produce amazing technological innovations and cultural insights. It thus can be valuable to consider these questions, albeit with the goal of introducing possible routes to answering them, rather than producing definitive answers. So, let us ask: how might aliens think? And, would they be conscious? Believe it or not, we can say something concrete in response to both of these questions, drawing from work in philosophy and cognitive science.

You might think the second question is odd. After all, if aliens have sophisticated enough mental lives to be intelligent, wouldn't they be conscious? The far more intriguing question is: what would the quality of their consciousness be like? This would be putting the cart before the horse, however, since I do not believe that most advanced alien civilizations will be biological. The most sophisticated civilizations will be postbiological, forms of artificial intelligence (AI). (Cirkovic and Bradbury 2006; Shostak 2009; Davies 2010, 153–168; Bradbury et al. 2011; Dick 2013). Further, alien civilizations will tend to be forms of superintelligence: intelligence that is able to exceed the best human-level intelligence in every field – social skills, general wisdom, scientific creativity, and so on (Kurzweil 2005, Schneider 2011a, Bostrom 2014). It is a substantive question whether superintelligent AI (SAI) could have conscious experiences; philosophers have vigorously debated just this question in the case of AI in general.

Most science fiction books and movies depict extraterrestrials (ETs) that are similar to us in many ways. They are at our scale, have eyes, limbs, and body symmetries. But what if they don't look like us? What if they are so different that no communication is possible? How would it impact our worldviews to find non-communicative ETs? I first argue that we will most likely find microbial life or what are known as Kardashev Type II stellar civilizations, but nothing in-between, and that any extraterrestrials we find will not communicate, for the simple reason that they would likely be either immensely inferior or immensely superior to us. Then, I show that the discovery of ET life will most likely be very slow, taking years or decades. Finally, to prepare for discovery, I propose a multidimensional impact model. Twenty-six dimensions are introduced, illustrated with spider diagrams, which cover both what extraterrestrials might look like, and how humans may react.

Why extraterrestrials will not communicate

The principle of mediocrity is fundamental in astrobiology. It says that, “we should assume ourselves to be typical in any class that we belong to, unless there is some evidence to the contrary” (Vilenkin 2011). Applied to our position in space in the universe, it means that our Solar System, our galaxy, and possibly our universe – if there is a multiverse – are typical. They are not central or special in any way. This insight is well known and well assimilated, and is also known as the Copernican principle. However, what if we apply it to our position in time?

If we map our position in time according to the Kardashev (1964) scale (Figure 4.1), we can see that we are in an extremely short transition phase from technical impotence to technical omnipotence. Indeed, the exponential growth of our energy consumption is very recent on evolutionary time scales, but will still be limited by the total energetic output of the Sun.

Contrary to common wisdom, science is not exclusively defined by its methods and theories, nor is it constituted only by substantiated empirical hypotheses. Rather, philosophical presuppositions are also a crucial part of the scientific endeavor. Astrobiology, like any scientific field that seeks to learn and understand nature, rests on such philosophical presuppositions. We do not experience nature as a clean slate, as the tabula rasa upheld by the seventeenth–eighteenth-century Empiricists. Philosophical presuppositions guiding science are general, universal claims about nature that transcend limited experience. For example, the notion that natural laws necessarily hold not only on our planet or in our galaxy but in the universe at large cannot be proved or disproved empirically. Nevertheless, it is on the basis of the universal applicability of natural laws that astrobiological research is conducted. Likewise, any other branch of the natural sciences could not function and advance without this principle. Furthermore, philosophical presuppositions express general guiding evaluations of reality that by definition are not open to observation or experience. The claim that nature was created and designed by an intelligent designer or the denial of this claim cannot be empirically settled. Yet, it is the notion that natural processes depend on natural causes and not on supernatural purposes which guides science.

Although the status of philosophical assumptions in science clearly differs from that of theoretical-empirical claims, these two elements are deeply connected. The interaction between the theoretical-empirical and the philosophical becomes apparent when science is examined historically. I argue that this interaction, shaped to a large extent by social and cultural factors, has resulted in the last few centuries in the establishment of the evolutionary naturalistic worldview. The major defining feature of this worldview is the rejection of supernatural teleology as necessary for the scientific study and understanding of nature.

Philosophical presuppositions of astrobiology

The natural sciences of today function within the framework of the naturalistic worldview. It is the robustness of this framework which provides validity also to branches of science that are still at the stage of establishing their fundamental data, notably the study of the origin of life on Earth and astrobiology. It has been claimed that the problem of the origin of life, yet unsolved, is the “soft underbelly of evolutionary biology” (Scott 1996).

One of my all-time favorite movies is the 1951 science fiction thriller, The Day the Earth Stood Still. It tells the story of an alien (Klaatu) who comes to planet Earth to say that the galaxy is pretty upset with us and fears that, with our new nuclear weapons, we might not just blow ourselves to smithereens but inflict significant damage on others. It turns out that the rest of the universe has put itself under the power of robots who enforce peace and quiet and if we do not mend our ways these robots will un-mend us once and for all. To make the point, Klaatu has brought one of the robots (Gort) along with him, and when as inevitably happens we humans fail to take proper heed and end up killing Klaatu, Gort sets out intending death and destruction. The carnage is prevented only because a young war widow (Helen Benson), who has befriended Klaatu and who has been told what to do in an emergency, manages in time to turn off Gort with the crucial words “Klaatu Barada Nikto.” I am sure I was not the only eleven-year-old who spent the next year uttering those words whenever I got in a jam. Somehow they never seemed to quite work with my schoolmasters.

Intelligent beings

Now, my point is that – with an interesting exception that I will mention shortly – Klaatu appears as a normal human being. Played by Michael Rennie without any special makeup, he rents a room in a boarding house in Washington DC, and causes no special attention when he appears at the breakfast table with the other guests. He goes off around the city with Helen's son Bobby and again there is nothing strange, although despite speaking English perfectly he does show ignorance of our ways – at the Arlington Cemetery grave of Bobby's father he fails to understand the point of violence and later naively swaps some precious diamonds for a few dollars. Physically, Klaatu is like a member of Homo sapiens and intellectually too. It is true that he is very, very bright, but not in a weird way. When he meets the physicist Professor Barnhardt – modeled on Albert Einstein – the two are clearly in the same intellectual ballpark.

Introduction

One of the seemingly intractable problems in addressing the impact of discovering life beyond Earth is the need to transcend anthropocentrism. How can we move beyond our preconceptions of basic concepts such as life and intelligence, culture and civilization, technology and communication? Unfortunately we cannot “get out of our heads,” so to speak, no matter how hard we try. But we can at least attempt to imagine a much broader spectrum of each of these concepts than are known to exist on Earth. Indeed, the best science fiction is sometimes very good at doing this. We can also attempt to escape our anthropocentrism by an empirical approach that emphasizes the diversity of life and intelligence on Earth, and potentially in the broader universe. Both natural and social scientists have begun to address these difficult problems.

In this section scholars from a great variety of backgrounds take up these issues. From his perspective in the biogeosciences Dirk Schulze-Makuch surveys the landscape of actual and possible life. He demonstrates that while the limits to life on Earth are much broader than once thought, other planets may exhibit even broader limits based on conditions specific to their planet, whether in the clouds of Venus, on dusty dry Mars, sulfur-rich Io, hydrocarbon-laden Titan, or the great variety of conditions sure to exist on the multitude of exoplanets now being discovered. All of this is based not on science fiction, but on possible real-life adaption mechanisms for life. In a similar way, neuroscientist Lori Marino examines the landscape of intelligence. Despite the importance of the concept to many fields (Sternberg, 2000; 2002), sophisticated studies in an astrobiological context have been lacking, with few exceptions (Bogonovich 2011). Decrying the lack of empirical work in this crucial area within the astrobiology community, she employs scientific data from terrestrial life to establish an expansive concept of the nature of intelligence. Intelligence, Marino argues, is not a binary property in the sense of having or lacking it, but is a continuous multi-staged and multi-leveled property based on the gradual evolution of life on Earth, beginning with the first neurons. Intelligence, she concludes, is a ubiquitous property of life on Earth; even if no life is found beyond Earth, “we are not alone,” in the famous phrase often used in the SETI context.

Science fiction novels and Hollywood movies have explored the subject of alien encounters for decades, but they provide little in the way of practical guidance on how humankind should respond to a verified discovery of extraterrestrial (ET) life. Today we are in the midst of unprecedented advances in our understanding of the potential for life in space. Without exaggeration, the prospects for finding ET life seem more likely all the time, raising questions of how well we are prepared to respond to a discovery. Do we Earthlings have the necessary plans and preparations for responding to potential risks and impacts of different discovery scenarios? Would it matter what kind of life is discovered first? Who would be involved in decision making on behalf of humankind?

This chapter takes a systematic approach to evaluating in detail how current decision-making processes and policies are prepared to deal with future discoveries and the associated risks and consequences of interacting with different types of ET life. It examines the three main search types (SETI, extrasolar planets, and Solar System searches), at three different search phases (during searches, upon discovery, and post discovery) and assesses comparative preparedness for systematic deliberations involving multiple stakeholders, scientific and otherwise. The evaluation borrows heavily from approaches used by the hazard-management and risk-analysis communities, which have extensive experience and research involving threats of many types, whether natural or man-made, and predictable, deliberate, or accidental (Alexander 2000; Eisner et al. 2012; Tierney 2014). In addition to providing a detailed comparison of current search efforts, this risk-centered approach also serves to highlight particular topics or procedural steps that may need more attention in order to develop practical and coordinated implementation plans for responding to any future discovery of ET life, whenever and wherever it may occur.

Putting searches in context

Before discussing the similarities and differences between current searches, it is important to recognize that there is no such thing as planning a response to the discovery of ET life, but rather multiple responses, built upon the characteristics of the different search efforts under way. Each anticipates different scenarios and types of life (intelligent, complex, or simple) as well as potential impacts, risks, and timeframes. In addition, each raises assorted questions that will require inputs from different perspectives – scientific and otherwise – regardless of who makes the first discovery.

In September, 2010, I had traveled to Birmingham, England, to give an astronomy talk at the Birmingham Science Festival. As it turned out, the day of my talk happened to coincide exactly with the visit of Pope Benedict XVI to Birmingham. I had agreed to be interviewed by the British press to publicize the festival, yet – understandably – all they wanted to ask me about was the Pope. But they kept asking me questions like, “What is your biggest source of conflict about the Pope?” Or, “Has the Pope ever tried to suppress your scientific work?” To my mind, these sorts of questions were bizarre; the mere existence of a Vatican Observatory ought to have shown them that their fundamental assumption about a hostility between the papacy and science was mistaken. Worse, the reporters seemed to be not at all interested in correcting that assumption, or hearing my description of the active support we had received not only from the Vatican in general over more than one hundred years, but more specifically from Pope Benedict himself. Finally, frustrated that they weren't getting the story they wanted out of me, one of them asked, “Would you baptize an extraterrestrial?”

My answer, off the top of my head, was, “Only if they ask!” It got a good laugh, which is what I wanted. And then, the next day, the press ran my joke as if it were a real story – as if I had made some sort of official Vatican pronouncement about aliens (Jha 2010). And that was merely the reaction of the relatively mainstream media. The more exotic wings of the internet were immediately full of wild interpretations, ranging from the thought that the Vatican was preparing the world for an imminent alien contact, to worries that somehow Jesus himself was an alien.

Of course, if these people had read their own newspapers, they could have found plenty of articles repeating this theme, over and over. For example, in 2008 the Vatican Observatory director, Fr. José Funes, SJ, had made essentially the same point in an article in L'Osservatore Romano and his comments had been widely reported.

Three broad approaches exist in the search for extraterrestrial biology: (1) discover life in the Solar System by direct exploration; (2) find chemical signatures for biology in the atmospheres of exoplanets; or (3) detect signals (radio or optical) transmitted by intelligent beings elsewhere. In this chapter I describe each of these approaches, and then elaborate the multiple ways that we might learn of technologically competent civilizations. I also discuss why society's immediate reaction to the discovery of extraterrestrial intelligence would be less dramatic than often assumed. In all three cases the search for life beyond Earth is the ultimate remote sensing project. With few exceptions (such as sample return missions) this is exploration at a distance. While some reconnaissance is done by spacecraft, the majority of the effort consists of sifting through information brought to us in a storm of photons, either optical or radio.

Introduction

The idea of extraterrestrial biology is hardly new, with written speculation on the subject dating back two millennia and more (Dick, 1982). The first scientific searches are more recent, beginning with Johannes Kepler who, observing the Moon in detail through an early telescope, thought he recognized features carved by rivers. These, he reasoned, were sure signs of biology. Kepler also believed that craters were the surface manifestations of underground cities constructed to protect the citizenry from the relentless sunshine of the two-week lunar day (Dick 1982, 75–77; Basalla 2006, 21).

These pioneering observations were plagued by naïve, anthropocentric assumptions and a lack of information on the true environments on these worlds. Such bugaboos continued to affect attempts to find cosmic company for centuries, extending to the enthusiastic study of Mars by astronomer Percival Lowell. In a series of books, lectures, and articles extending from 1894 until his death in 1916, Lowell proclaimed the existence of a vast, hydraulic civilization on the Red Planet (Crowe 1986; Dick 1996). Just as Kepler had done, he appealed to morphological evidence – straight-line features that he interpreted as canals – to back up these assertions. Lowell's claims were spurious, although one could argue that the falsity of his discoveries was due more to poor observation than poor interpretation (the trap that had snared Kepler). If the linear features described by Lowell actually existed, they would have been compelling evidence for intelligent beings.

If the search for extraterrestrial intelligence (SETI) detects an artificial signal from a distant civilization, our next challenge will be to understand any encoded message, and then to decide what we may want to transmit in reply. The few intentional messages humans have sent into space thus far reflect the assumption that mathematics and science are universal. Any civilization able to build technology capable of interstellar communication must certainly know at least the basics of these areas, it is often argued. How accurate is this Platonic notion that our math and physics tap into universal principles? Might different civilizations have their own versions of math and science that are perfectly adequate for explaining the universe, but that do not directly map onto our notions?

Lingua Cosmica

In the standard approach to constructing interstellar messages that may be comprehensible to an independently evolved intelligence, we start with concepts presumably shared by sender and recipient. If the goal of interstellar communication is to share information not previously known by the recipient, the sender has the additional challenge of identifying a sequence that will lead from shared to unique information. For example, logician Hans Freudenthal began his interstellar language Lingua Cosmica, or Lincos, with an exposition of mathematical concepts (Freudenthal 1960). He then moved to a discussion of time; then human behavior; and finally notions of space, motion, and mass. In the process, he attempted to convey some of the idiosyncrasies of human life in terms of potentially universal principles of mathematics and science.

A recurrent critique of Lincos is that ambiguities at one point in the exposition may make subsequent sections unintelligible. In this chapter, I examine the potential problems raised by Freudenthal's reliance on concepts related to infinity early in his message, and propose an alternative approach that introduces notions of three-dimensional (3D) space and motion as a foundation for discussing human behavior, with the goal of enhancing intelligibility.