1. Introduction

The search for microbial life on places like Mars and Jupiter’s moon Europa, has in recent years become an objective for scientific research (Goertzel and Combs 2010; Naganuma and Sekine 2010; Rampelotto, 2010). Discoveries indicating the former existence of liquid water on or near the Martian surface and methane on Jupiter’s moon Europa (See eg. Malin & Edgett 2000, Kerr 2006, Tritt 2002, Jones 2001, McCollom 1999) have made discovery of life elsewhere in the Solar System seem possible, perhaps even likely. We already know that on Earth, microbes called extremophiles live and thrive in conditions that are extremely hot or cold, saline or toxic from a human perspective (Satyanarayana et al. 2005.) There is a distinct possibility that various prokaryotic species and fungi could be found on Mars. It is well known, that Mars was long ago a very wet and much warmer planet which was conducive to the origin and evolution of complex life (Russell and Hall, 1999; Yung et al., 2010), but because of changing geochemical forces which effected energy flow it became impossible for complex life to dwell upon the surface or to continue to evolve. However, because of the suspected presence of water beneath the soil, a complex biosphere may still be present beneath the surface (Hartman and McKay, 1995); if there is also organic residue, there would be enough energy to drive autotrophic metabolism (Weiss et al., 2000).

The possibility that Mars is a living planet is supported by evidence from the 1976 Viking Mission Labeled Release (LR) experiment (Levin 2010). As determined by Levin (2010), the LR obtained positive responses at Viking 1 and 2 sites on Mars which was at first interpreted as indications of life. Almost immediately, however, a consensus formed which favored chemical or physical agents in the Martian surface material, not life. Science is not a democracy and a positive response favors the possibility of life. In fact, the positive response to the LR experiment can be explained by microbial organisms which employ use a mixture of water and hydrogen peroxide as an intracellular solvent (Houtkooper and Schulze-Makuch 2010).

Additional evidence suggestive of life is based on the presence of substantial amounts of methane in the Martian atmosphere (Yung et al., 2010). Although it is yet to be determined if the methane is biological or abiogenic, the fact remains that methane continues to be produced. Even if abiotic in origin, the combination of reduced gases and oxidised minerals provides opportunities for life to flourish (Sephton 2010).

Based on studies of genetics, biology, and astrobiology, there is a growing consensus that life on Earth originated from extra-terrestrial sources, and were delivered to this planet by comets, meteors and planetary debris (Jose et al., 2010; Gibson and Wickramasinghe 2010; Joseph 2009; Joseph & Schild, 2010; Sharov 2010); and this implies life may be everywhere throughout the cosmos. If life on Earth arose by mechanisms of panspermia or through abiogenesis, then certainly the same mechanism can apply to Mars and other celestial bodies. And even if life first arose on Earth, it is possible life could have been transferred to Mars from Earth by mechanisms of panspermia (Burchell 2009; Napier and Wickramasinghe 2010). There is thus every reason to suspect that life may exist on Mars, and that highly evolved forms of life have evolved on other planets (Joseph and Schild, 2010; Mitchell and Staretz 2010).

"Space junk" has already become a problem and poses dangerous and potentiality catastrophic risks to astronauts. Species destruction and environmental damage is also more or less uncontrolled (Ceballos et al., 2010; Cains 2010; Moriarty and Honnery 2010; Reese, 2010; Trainer 2010). Many believe we are facing a 6th extinction crisis (Ceballos et al., 2010; McKee 2010; Jones 2009; Tonn 2010). Clearly our existing moral principles when it comes to life and the environment are far from ideal. Perhaps we should be careful not to continue exploring space based on the same values we employ on Earth. One important benefit of space exploration could, therefore, be philosophical in nature: developing a sustainable model of exploration and exploitation of environments. Jacques Arnould and André Debus have argued that ethics is in some sense the next frontier of space exploration (Arnould & Debus 2008).

The possibility of discovering life in places like Mars also raises several important philosophical and ethical questions. Addressing these questions in advance, before anything has actually been discovered, is important. As McArthur and Boran (2004) have noted, humans have a deplorable record in dealing with each other and with their fellow species here on Earth. According to them, it is possible that speculating about our moral obligations towards extraterrestrials serves as a call to improve our record here on Earth (McArthur & Bodan 2004, Cockell 2007). Philosophy of space exploration is similar to the technology of space exploration in that it has the potential to improve the lives of many of those who are not directly involved in the exploration effort. The current declining state of our environment (Ceballos et al., 2010; Cains 2010; Moriarty and Honnery 2010; Reese, 2010; Trainer 2010) proves clearly that our traditional way of evaluating environmental ethical questions is far from sound (Ceballos et al., 2010; McKee 2010; Jones 2009; Tonn 2010). But theorizing will not be enough. As Mark Williamson (2006) has noted, environmental ethics (of which space ethics can be seen as one subcategory) is, and should be, practical ethics. Philosophical research related to space exploration not only has the potential of producing better understanding of how we should act in space – it could also guide us into treating our own planet more gently. In these times of climate change, widespread species extinction and other threats to the global ecosystem, this knowledge would be of extreme importance. Space and any possible ecosystems on other planets, may represent a fragile frontier (Williamson 2006). Among other things, this could mean that errors in moral judgment are in many ways more serious and less easily repairable than errors made on Earth. In this paper, I will introduce and develop the concept of sustainable exploration. I suggest that virtue ethics is an ethical theory well suited to space exploration, and that sustainability should be a key virtue for space exploration. A manned Mars mission will be the most ambitious exploratory effort humanity has ever undertaken. It should go into history books as an exploration mission where we for once got things right, not just in terms of technical success, but also in terms of ethical excellence.

2. On the concept of Sustainable Exploration

The human race should not simply explore space. For moral beings, all choices, actions and activities also have a moral dimension. Space exploration is no exception: our policies and decisions always reflect our underlying moral values, whether we are conscious of what those values are or not. We can explore space economically, in a spirit of international cooperation and peace. It is easy to see how these underlying abstract principles can have a huge impact on the manner in which the actual project is carried out. So, I suggest that we should, above all else, explore space sustainably.

Sustainable exploration means considering all our activities from a wider historical perspective and taking into account the long term consequences of our planned actions. It is closely related to Aristotle’s concept of prudence (Aristotle 1980.) According to Aristotle, a prudent person is one who is able to deliberate carefully concerning what is good and expedient for his living well in general, not only in questions regarding some particular, small-scale matters. In other words, a prudent person is one who can see the big picture behind everyday decisions. Such a person understands what are important constituents of a good life and what are less important or even harmful in the great scheme of things, and is able to make his moral decisions accordingly.

In space exploration, seeing the big picture is difficult. While few space professionals would actually advocate a slash and burn philosophy for space exploration, some have also advocated the exploitation of land rights and mineral resources of Mars so as to fund a mission to Mars and the colonization of the red planet (Joseph 2010), and some might choose to turn a blind eye to the occassional pollution or degradation event in favor of budgets, project timelines or personal advancement (Williamson 2003). Space exploration is no different than other ambitious pursuits, in that lowering and compromising ethical standards often seems beneficial. This "benefit" usually refers specifically to short-term benefits as seen on Williamson’s examples. The "human nature" mentioned by Williamson, can be interpreted to mean the persistent human tendency to think that temporal closeness means greater importance. The concept of sustainability can challenge this view. However, it needs to be incorporated into the architecture of the exploration effort, specifically into the COSPAR planetary protection policy (COSPAR 2005, Rummel et al. 2010), and not left as a concern of individual researchers or project participants.

Explorative science is characterized by the need to act in epistemically imperfect conditions, that is, in conditions characterized by uncertainty and ignorance about facts normally considered important for moral decision making. In a new environment, it is very difficult to properly anticipate all possible scenarios or weigh the actual risks attached to suggested actions. In a Mars mission, this condition is highlighted since communication to Earth will be slow. Astronauts will need to be able to make big moral decisions independently, without consultation with the mission control center on Earth. In making such decisions, there is great ignorance regarding important factors that might affect our decisionmaking. In risk theory, Aven and Renn (2009) have stated that "Risk refers to uncertainty about and severity of the events and consequences (or outcomes) of an activity with respect to something that humans value." Arnould and Debus (2008) have elegantly summed up the problem: in an ideal world, we would wait until we understood things before we did them. But in the actual world, we usually need to act in partial ignorance in order to gain understanding. Somewhere along the journey from ignorance to understanding, is experience.

Science, by definition, is all about making that journey of discovery. The beginning of sustainability, then, is acknowledging this need to act in ignorance and adopting an ethic that can work under these conditions. In space exploration, the risks can not be reliably measured and all possible outcomes of actions can not be anticipated. For the purposes of moral decisionmaking, risk analysis does not work well in an exploration situation. Fortunately, there are better alternatives available.

3. The Difference Between Restriction and Protection

The goal of exploring extraterrestrial life combines several important human interests, as well as some of the most fundamental questions we have ever posed. In virtue ethics, a "good choice" equals "the most sensible choice in the long term, all relevant things considered". Not only is sustainable exploration morally praiseworthy, it is also of important human interest in its own right. While simply finding extraterestrial life would be an important discovery, we also wish to study the new kind of life and to learn from it. Therefore, making sure that life is not destroyed in the process of discovering it is of utmost importance and consequently, exploring in a certain way (ie. a way that avoids the realization of this and other risks) is in our best interest.

Second, sustainability is a concept that unifies several important values, such as those identified by Cockell and Horneck (2004): intrinsic worth, responsibility to future generations, protection of sites of natural beauty, utilitarian value and historical value. The term "restriction" is neutral in the sense that it merely says we should refrain from acting in a certain way. I prefer to use the term "protection" because it also refers to the reasons why we want to refrain from doing harm. We restrict and protect for a good reason: because we want to preserve future interests of all relevant parties and avoid short-sightedness. The term "protection" also implies that sometimes it is right not just to refrain from acting, but to take positive action in order to ensure that important interests are protected. These interests might be our own, or they might be those of future generations. They might even relate to life forms or an ecosystem itself, or more plainly speaking, to an understanding that any life might have interests of its own; for instance, it is reasonable to say that all life has an interest to survive and avoid becoming extinct. As Mark Lupisella (1997) has noted, we must, as a global society, try to understand what position nonsentient extraterrestrial organisms will occupy in our ethical and political framework. More broadly speaking, we should be sensitive towards space environments out of respect for the fragility of lifeless environments and the promises for their future potential as living planets. This kind of statement is an answer to the question: "What kind of moral attitudes should explorers have?" It calls for an agent-centered ethic. Normative reflection should be concerned primarily with identifying the responsibilities of researchers and explorers (McArthur and Bodan 2004).

The constraints humans ought to impose themselves should be principle-based, that is, the basis for ethics should be moral principles instead of efficiency or short-term results. Some have suggested a deontological approach, but to me it seems that a virtue ethical approach would work even better. Deontological ethics consists of those ethical theories where the general idea is to identify a set of good moral rules and define praiseworthy action as adherence to these rules (for further information on deontological ethics, see eg. Stanford Encyclopedia of Philosophy). Virtue ethics, on the other hand, is all about principles, attitudes and motives. As such, it is also suitable for poor epistemic conditions that characterize space exploration. It is, after all, difficult to understand how we could find good rules to guide actions that take place in environments that are poorly understood. Even if we could identify some rules, it is easy to imagine new and surprising situations where strict adherence to these rules would be disastrous and the reasonable course of action would be to make an exception. However, a moral agent always has access to reliable knowledge considering his or her own attitudes, motives, and the particular moral principles that are currently being applied in this particular situation. Improvements in the epistemic condition, that is, when our explorer gains more information via studying the object of his or her interest, certainly help virtue ethical moral decision making. But one can begin with much less, and, if one acts wisely, the moral decision making process can still give the agent recommendations that are sustainable more often than not. In comparison, a consequentialist –someone who tries to foresee the consequences of all potential courses of action and base his or her judgment on risk/benefit analysis– needs to be well informed in order to be able to reliably determine the best possible course of action. When sufficient information is not available (as is necessarily the case when we explore space environments), he must resort to uneducated guesswork before he can act. If it later turns out that his guess went wrong, the results can be disastrous. The deontologist is not much better off. The constant problem in a rule-based ethics is, that if the rules are made flexible enough to enable one to act in completely novel situations, they probably are not practical enough for providing effective guidance and vice versa.

Let us consider an explorer who decides that his or her research subject is a nonsentient life form. This explorer’s ethical system allows nonsentient life forms to be subjected to painful examinations while such examinations would be forbidden on sentient beings. It is easy to see that a mistake in evaluating the object’s sentience would lead to a grave error. For all we know, such a mistake might be easy to make when beginning to study life forms that have evolved on another planet. A theory that contains a high risk of such errors can say that such errors are not so serious after all. This is, in my opinion, an intolerable position. Should not moral philosophers of all people take the subject of their own study seriously? Another option is to say that such mistakes are regrettable but unavoidable. The latter option does not make an ethical system look very attractive, because it essentially says that our best efforts are doomed to fail sooner or later, and when that happens, we have a good reason to be sorry. I think that a good ethical approach is one that makes moral success genuinely possible and moral failures avoidable (at least in principle.) It is one that states that it is not only important, but also possible and rewarding to take ethics seriously.

4. Sustainability and Benevolence

The key ingredient to successfully practicing agent-prior virtue ethics, is a set of core values instead of rigid guidelines. This core will enable the agent to adapt himself to new situations. Furthermore, while rules can sometimes be seen as arbitrary and impractical by the people who should put them into practice, the value approach highlights the fact that ethics is a tool and an essential component for making good science. It guides us to make excellent science rather than delaying progress. The practical manifestation of a sustainable attitude could be the principle of caution: avoid harming that which you do not yet understand, and try to avoid causing harm you are in practice unable to repair. These guidelines should be understood as rules of thumb rather than strict rules. Exceptions to rules that are meant to guide actions in alien environments are not only easily imaginable but also sometimes necessary. That is not a weakness of the virtue approach, but on the contrary, it is precisely the feature that makes it as flexible as necessary for an ethical framework to be when acting in epistemically poor circumstances.

Benevolence is another concept widely considered as a key virtue. It is a virtue that directs us away from self-centeredness. Benevolence also has its intellectually appealing side: in order to successfully express our benevolent attitudes we need to understand something about what constitutes good for another being(s). Geoffrey Frasz (2005) observes that benevolent treatment of nonhuman entities is a necessary attitude for good stewards of the land. Sustainable space exploration can be seen as an extension of Frasz’s idea: sustainable explorers are those who are good stewards of their sphere of influence whether that sphere physically exists on Earth or in space. Frasz’s view also illustrates another important feature of environmental virtue ethics: the important aspect in ethics is not to evaluate how much other beings resemble us in terms of properties we value highly, such as intelligence and sentience. Goertzel and Combs (2010) present a very interesting discussion on how subjective many such "values" could be. Their thought experiment suggests that many familiar concepts such as "causality," "individual self" and "technology" might not exist at all in intelligent life forms that have evolved in complex fluid environments. This is precisely the sort of sensitivity that should be developed further in environmental ethics, where concepts such as sentience are often used as explanations for why some species deserve better treatment than others. Rather, virtue ethics focuses on evaluating beings we understand very well: ourselves and human action. When understood as an aspect of sustainability, benevolence is well suited to the role of a guiding virtue of explorers. Benevolence not only understands but encourages intellectual curiosity. In order to truly determine what is in the best interest of the other, one needs to gather information about the life and concerns of the other (Frasz 2005). The interests of ethics and science are in the end the same thing viewed from different perspectives.

Sustainable exploration of space does not mean that we should be so sensitive to interests of others that we cease to pursue our own interests. There are good reasons to place a high priority on the needs of Earth and most current human space-related interests. What is important is the manner in which we choose to pursue those interests (Reiman 2009). Virtue ethics can be applied to answer questions such as:"How far is it right to go when pursuing intellectual interests?" and "When should we start balancing scientific interests with other important concerns?" In light of the concept of benevolence, we are able understand that (scientific) curiosity is good, but it must be balanced by concern for the well-being of others and the adviseablity of acting responsibly. In essence, a benevolent attitude is one that hits the right balance between our own interests and the interests of others, be they future generations or other species.

5. Leaving Kansas

As Williamson noted, space explorers seldom openly advocate unsustainable goals. This is a very important observation. It highlights the fact that it is not sufficient for the moral community (such as the space explorers) to agree in theory that protection of space environments is good and that we should avoid harming extraterrestrial life forms. If the goal is to explore space in a truly sustainable manner, we need a deep understanding of what abstract ethical concepts such as "harm" and "protection" mean, as well as a working vision of how to turn the abstract values in practice. We need to know how to mediate the interests expressed by the concept of sustainability with our scientific, economical and political interests. If the exploration effort is not specifically analyzed from an ethical perspective, unsustainable motives and background assumptions easily get on board of our spacecraft. Let us consider a dramatic historical example, the Viking biological experiment. This experiment was carried out by Viking landers, which were part of Viking Mars exploration program in the 1970’s (Klein et al 1976; Levin 2010). The concerns voiced here may also apply to any sample-gathering missions, such as the planned Mars Sample Return missions. In the Viking biological experiment, one of the experiments performed was a pyrolytic release experiment. In the experiment, a soil sample was baked in 650 °C, and the products were collected in a device which counted radioactivity. If any of ¹⁴C had been converted to biomass, it would be vaporized during heating and the radioactivity counter would detect it as evidence of life. Should a positive response been obtained, a duplicate sample of the same soil would be heated to "sterilize" it. It would then have been tested as a control, and had it still shown activity similar to the first response, that was evidence that the activity was chemical in nature. Needless to say, any Martian life contained in the sample would have been destroyed in the process.

The test was based on an assumption that loss of the microbia contained by two samples is a minor one, and therefore morally acceptable when weighed against the chance to provide evidence for existence of Martian life. However, it seems to me that labelling the loss of life as insignificant is an evaluation that is heavily based on the conditions on Earth. Here, it is true that wherever there are microbes, there are usually plenty of them so that taking a moderate sample will not endanger the continued survival of the colony, much less the species. Even if Mars does have indigenous life, microbial colonies are expected to be sparse ( Cockell & Stokes 2004, Warren- Rhodes et al., 2007a,b,c.) But how sparse, exactly, are we talking about? All we know for certain is that life there (if there is any at all) is much more scarce than life on Earth. The loss of a microbial colony could be significant in a world where few struggling microbial colonies are the only type of life left. If we apply the virtue of sustainability to exploring life on Mars, we will see that it becomes imperative to determine (instead of assuming how things are based on how they are on a thriving planet) how common life is, and learn what actions would cause major risks for its continued survival. Charles Cockell (2005) says that only when contamination (or other damage caused by human activities) results in large-scale killing of indigenous microbial communities that threatens the integrity of biotic communities, should we then have concern about our effects on them. This principle is one that can be applied both on Earth and on Mars. However, the practical meaning of this principle in practice can be very different depending on where it is applied. On Earth, we may be able to carry out most experiments without needing to worry much about the well-being of microbes. Based on vast experience we can safely say that taking samples in the process of studying microbial life forms previously unknown to science will not cause their extinction. On Mars, the same principle may tell us to exercise great caution in order to ensure that we do not cause irreparable harm. Finding answer to the question "What actions could cause irreparable damage?" is therefore imperative. We need to be able to answer the question of the existence of life without conducting experiments that, to our best knowledge, could lead to loss of life.

We can apply these ideas and form more practical guidelines, such as the ones below:

Principles of caution should be observed strictly. Making assumptions that fail because they are not based on facts is all too easy. It is even easier because in some cases –such as in the case of microbes- we easily fall into thinking that we have good scientific knowledge about microbes in general, for instance that microbes are unable to experience pain. The problem with this approach, naturally, is that we have learned everything we know by studying life forms of Earth. Whether or not Martian microbes fit into our general idea of what a microbe is, remains open until proof pointing to one conclusion can be found. Therefore the ethical validity of research guidelines that have been used on Earth needs to be reviewed before applying them elsewhere. For instance, while it would be morally acceptable to subject a specimen from a microbial species X to tests that aim at resolving the question of its ability to feel pain, it would be morally unacceptable to adopt any foreseeably pain-causing methods as standard research methods prior to establishing the fact that X is unable to experience pain. For all we know, we could run into a hive mind, or an organism that is so large that astronauts have discovered only one of its organs…or something that we can not even imagine. The potential of discovering something completely new and unbelievable is one thing that makes space exploration so exciting. The same element of surprise and the need to expect the unexpected makes the practice of responsible and sustainable exploration such an interesting ethical challenge. When we are in space, we truly are not in Kansas any more.

6. Objections to the Sustainability Approach

The objection towards sustainability approach is clear. Williamson (2006) has shown how sustainability ideology taken to extreme slows down, or even halts progress. Even more moderate sustainability can slow down progress significantly compared to how fast progress could be achieved by "brute" methods that do not consider sustainability aspects. Storming a planet is certainly more effective and bound to yield impressive results quickly compared to careful treading. Also, sustainability is usually not the most cost-effective approach on the short term. This "inefficiency" is enhanced by the fact that for the most part, space exploration is project-centered research where results are evaluated separatedly for each project. Understanding the long-term impact of a research project must be carefully considered in order to survive such a research environment. This is, however, a distinct possibility on a mission that contains the possibility of discovering extraterrestrial life for the first time. Furthermore, it should be noted that ethical excellence of many existing research practices is questionable (as seen eg. in debate over moral acceptability of animal experimentation.) If the Mars mission will indeed become the first exploration mission with improved understanding of sustainable and ethically responsible practices, the people working on it need to take a critical look at conventional methods of making science and project architecture. The ethical challenges and opportunities a manned mission to Mars may provide are in many ways just as exciting as the technological challenges.

The main difficulty for adopting sustainability as the key virtue for space exploration is that the whole point of sustainability is to shift focus from the impressiveness of immediate results to securing (among other things) our long term research interests. As illustrated by the Viking biological experiment, exercising sustainability also means that we become aware of our own preassumptions and ignorance affecting our moral evaluation processes.

Other objections towards my approach are general objections towards virtue ethics at large. I have already pointed out that the ambiguity of moral principles instead of well-defined rules is actually a benefit when applying virtue theory to space exploration. Other objections towards virtue theory are more theoretical (eg. Solomon 2003 has shortly summed up some common objections as well as a defense against them) and do not directly concern the applicability of the virtue approach to space exploration. For instance, the questions regarding the nature of good life are not ones that the space exploration community needs to be able to answer.

7. Conclusion

There are critical philosophical questions underlying the goal of discovering extraterrestrial life. "What kind of explorers do we wish to be?" and "What kind of humanity do we want to take to space?" are examples of such questions. As we explore space, we will also explore ourselves as a species. What we learn from this exploration can affect on how we choose to pursue good life on Earth. Many of the background assumptions we operate on here will no longer work as intended in space environments. One such example is the possible scarcity of microbial life in environments like Mars. When developing research methods, we must become aware of such background assumptions and adapt our moral decision making system to these conditions. Failure to do so might lead to making grave errors in judgment.