1. Two Visions of Mars

Before he became the Roman god of war, Mars lived a pacific life as the protector of farms, crops, and animals. He was loved by Romans as the father of Romulus, founder of Rome. This made Mars the celestial father of the Roman people. Mars began to change as the Roman Empire changed. While farmers continued to pray for his protection, so did the imperial legions which left the Italian peninsula on expeditions of conquest. In the first century BCE, therefore, Mars represented two things at once. He was the giver of life, the guardian of agriculture. He was also the blood-stained warrior, the defender of soldiers marching at the frontiers of the known world. While Romans may have been united in their love of Mars, they looked to him for different reasons (Leeming 2005). Despite the change from god to planet, Mars continues to mean different things for different people. On one hand, it is an archive of the past, a planetary laboratory where scientists seek answers about the history of the solar system and the origins of life. On the other, it is the landscape of the future, the next human frontier, the first real step out of our planetary cradle.

These different visions of Mars – as science laboratory and human frontier – seem complementary. On the science side, mission planners have long defended robotic expeditions for their value in paving the way for human exploration. Mariner, Viking, and Pathfinder all found justification as the trailblazers of human missions. The Jet Propulsion Laboratory defends its newest project, the Mars Scientific Laboratory, on similar grounds: as a mission that will "prove techniques that will contribute to human landing systems." (NASA 2010).

Advocates of human spaceflight also defend the compatibility of human exploration and science, often by arguing that humans are more effective in doing science than remotelyoperated probes. As Mars Society president Robert Zubrin declares, Martian science "is a job for humans" (Launius and McCurdy 2008).

Despite this apparent compatibility of visions of Mars, plans to sent astronauts to Mars have repeatedly failed. The Constellation Program is only the most recent Mars project to come up short. Wernher von Braun championed the idea of human Mars expeditions in the 1950s, followed by the Project EMPIRE study of the 1960s, the Space Task Group plan of the1970s, the Space Exploration Initiative in the 1990s, and the Vision for Space Exploration in 2000s. For those looking to place boots on Mars, NASA seems to be drifting in a Sargasso Sea of underfunded programs and policy revisions, never able to chart its course for the New World.(von Braun 1952, NASA 1989).

2. The Failure of Human Programs

What explains the failure of human Mars programs? There are many answers. The lack of sustained commitment in the executive branch, the fickle nature of Congress, and the capricious interest of the public are routinely cited as causes. Yet this blame is misplaced. Lukewarm support for human spaceflight has been the rule rather than the exception over the past fifty years. As such, it should not be seen as the cause, but as the climate in which Mars programs must adapt to operate (Launius 2010).

Instead, the key problem exists within the space community itself: a basic disagreement over the meaning and purpose of Mars exploration. While the compatibility of different visions of Mars – as a place of science and human exploration – is real, it is paper-thin. Consensus over aims is easy to attain when the basket of goals is broad; science, national prestige, and human progress are all popular motives for exploring Mars. Yet these goals routinely come into conflict. Expensive missions and tight federal budgets force choices over the goals of Mars exploration. While most members of the space community would embrace the set of goals as a whole, they tend to be committed to one goal far more strongly than the others.

For example, many space scientists express frustration with human space flight, which they view as an expensive distraction from scientific exploration (Launius 2006, Lester 2010) Lower costs, improvements in computer design and miniaturization, and the proven durability of Martian probes have encouraged their faith in robotic science and made arguments for sending astronauts to Mars less compelling (American Physical Society 2004). By contrast, many supporters of human missions to Mars believe that the focus on science and robotic exploration has become too narrow, ignoring the deeper meanings of exploration, its capacity to inspire people today, and shape the societies of tomorrow.

3. Debating the Premise of Exploration

Differences in vision cannot be settled by debating points of policy or mission design. While it is popular to think of debate as an activity that accentuates differences, the crucial element of any debate is identifying points held in common. What are the beliefs or axioms that both parties accept? What are the common values that lay beneath differences in policy? These values are often so basic, so tacitly accepted that they are never discussed. Yet Richard Nixon did discuss them in his famous televised debate with John Kennedy in 1960. Before he engaged Kennedy in arguments about health care, he established the values that united both men:

Without a common premise, debates over policy yield little. If Kennedy's position had been to publicly dismiss "old people" as a waste of time and federal dollars, it’s hard to see how a debate with Nixon on health care would have brought clarity to the issue. In this fictional scenario, Nixon's critique of Kennedy’s shortcomings on health care would, in Kennedy's value system, be taken as a compliment. The point is this: matters of policy are almost impossible to decide when the basic values underlying these policies are also undecided.

How do we best explore Mars? For space scientists, the key term in this question is the object "Mars;" the goal of exploration is the investigation of our planetary neighbor. According to this framework, Martian probes Spirit, Opportunity, and Phoenix are explorers. Indeed, supporters routinely personify the probes as if they were sentient beings, personifying them in name and behavior (such as giving them their own twitter accounts).

For proponents of human missions to Mars, the key term in the question is the subject "we." According to this line of thinking, exploration is an activity that requires human travelers to teach us things about Mars, but also to be our proxy, to teach us things about ourselves. For these members of the space community, "robotic exploration" is incomplete at best, oxymoronic at worst. Despite the successes of the robotic Martian program, for example, former secretary of NASA Mike Griffith recently told the Mars Society that "A real space program goes somewhere, goes somewhere worthy, it does something worthy when it gets there." It is clear that Griffith does not see Spirit, Opportunity, and Phoenix as the core of a "real space program" regardless of their mechanical or scientific accomplishments (Foust 2010).

In short, the debate over Mars is really a debate over the nature of exploration itself. It will not be solved by news designs for booster or crew capsules. While robotic missions may not generate the excitement of human ones, they have become a proven means for gathering data about Mars at reasonable cost. What would human missions give us? Advocates have not effectively made their case. Too often, they have gotten lost in the estuaries of Mars debate: on the benefits of future technological spin-offs, new aerospace engineering jobs, or a national advantage in space.

However realistic or important these benefits may be, they are the windfalls of discovery, not its object. To say that we should spend a trillion dollars to send astronauts to Mars in order to employ engineers and develop spin-offs is like saying that we built the Empire State Building because of its excellent views of Manhattan. The promise of jobs and new patents may temporarily boost Congressional and public support, but they will not sustain it; they do not offer a compelling motive that would support such projects over the long haul. Sending humans to Mars requires a vision of exploration that convincingly explains why we should place humans at the center of an exploration program despite risk and expense (Logsdon 2003).

For the pro-human camp, making this case is difficult. The core aims of Mars human missions attach to goals that are hard to measure: ensuring the survival of the species, inspiring new generations, fulfilling a human destiny to explore, or fostering social or biological evolution. While all of these goals are important, they are visionary, long-term, or intangible. As such they are tricky to assess as matters of policy. How much would a Mars human space program inspire young people? What are the key threats to our species survival? Would they best be met by sending humans to Mars? What is the metric for measuring exploration as a creative or evolutionary activity?

4. The Problem of Historical Analogies

While JPL engineers can design probes to answer specific questions about Martian geological history, questions about human destiny, inspiration, and survival cannot be answered directly. As a result, advocates of human spaceflight often use comparative or analogous forms of reasoning to make their case. In her extensive anthropological study of human spaceflight programs, Valerie Olson observed how these programs depend heavily upon analogical planning and reasoning (Olson 2010). The analogies come in many forms: from data-gathering analog programs such as NEEMO and Desert RATS which test humans and equipment in extreme environments to the use of historical analogies that link spaceflight to earlier eras of terrestrial exploration.

When we peel away the ancillary arguments for human spaceflight (e.g. benefits to spinoff technology, employment, or national soft power) we find that core arguments rely heavily upon the use of historical analogies.

For example, a common historical argument posits that human spaceflight nourishes a human need to explore, connecting us with our expeditionary ancestors: prehistoric migrations out of Africa, the European exploration of the New World in the 15th and 16th centuries, and the U.S. exploration of the West in the early 1800s (Lester and Robinson 2009, Robinson 2009). In making this argument, supporters frame human spaceflight as a natural extension of these earlier efforts. By this line of argument, exploration is not merely a practical or inspirational, but an instinctive behavior. In 1970, J. R. L. Anderson described the drive for curiosity and wanderlust as "the Ulysses Factor," an exploring instinct encoded within the human genome (Anderson 1970). More recently, Stephen Ashworth expressed a similar idea in his 2009 Space Review essay, "Darwin and Evolutionary Progress to the Stars":

Even President Bush implied that exploration was a human instinct that cannot be overruled. In his speech introducing the Vision for Space Exploration (VSE), he stated that "This cause of exploration and discovery is not an option we choose; it is a desire written in the human heart." (Bush 2003). NASA’s 2004 VSE promotional literature featured the President’s quotation prominently on its front cover. In making these claims, proponents frame human spaceflight as the natural, perhaps inevitable path of human progress in the future.

Yet there is little evidence to show that exploration is an instinct. Only a tiny percentage of people in any society can be called explorers or adventurers, thus a desire to explore could hardly be called a ubiquitous trait in humans. Indeed, the lesson from history appears to show the reverse: that humans have sought out an increasingly settled lifestyle based upon agriculture and industry, foregoing the risks of nomadic travel. The migrations of prehistoric peoples may look to us like bold expeditions into the unknown but this was almost certainly not the case. As science writer Nicolas Wade explains:

In tracing the movements of the first modern humans across the globe, geneticists’ maps show neat arrows stretching from eastern Africa to India, Australia, or Japan, and the arrows unavoidably give the impression that the emigrants were purposefully traveling to these distant endpoints. But of course they were not – they had no maps and no idea of what lay at the end of their journey. In fact, it’s doubtful they were on a journey at all (Wade 2006).

Later explorers did have maps and goals, but they were rarely driven by impulse. Christopher Columbus, Vasco da Gama, and Bartolomeu Dias, for example, all sailed in hopes of bringing back riches, glory, and knowledge of trade routes. Curiosity was low on their list.

Yet even if we were to accept the pro-human spaceflight argument that the desire to explore is natural or instinctive, it doesn’t explain why we should obey this impulse. To say that we should do something because it is natural is to fall into the classic "naturalistic fallacy."(Moore 1903). This line of reasoning has been used repeatedly in history often to ill-effect. In the 1800s, for example, Social Darwinists used nature to justify poor treatment of workers and colonial subjects on the idea that survival of the fittest was natural and therefore should be allowed to run its course. Even if one decides, against better judgment, to label humans as "born explorers" it does not follow that we should explore. Human missions to Mars need to be justified on better grounds.

5. Conclusion

The divide over Mars is deep. It extends to basic beliefs about the meaning of exploration. While a scientific vision of Mars, with a focus on tele-robotic exploration, may not excite the public, it is achievable within the current fiscal climate. Moreover, the value of such tele-robotic missions can be measured by the amount and significance of data gathered. By contrast, human missions to Mars will be exceptionally expensive and will rely upon long-term, intangible, and visionary arguments that are much more difficult to assess. In the past, advocates of human spaceflight have relied upon historical analogies to make their case, even when those analogies have been faulty and simplistic. So where do we go from here? Should we send humans to Mars? The case still needs to be made. One thing is clear: humans will not reach Mars on the power of peripheral arguments about science, national pride, or technological spin-offs. Advocates of a human program need to articulate the core values of human spaceflight and justify their missions accordingly, even if they are difficult to measure.

Perhaps the best historical analogue for Mars is not the voyage of Christopher Columbus or the journey of Lewis and Clark but the polar expedition of Robert Peary. In 1908, Peary made his final dash for the North Pole. Unlike earlier explorers who has tried to unite the activities of science and discovery together, Peary abandoned this strategy, foregoing science in the pursuit of being "first at the Pole." It wasn’t that Peary, trained as an engineer and a member of the AAAS, scorned science, rather he understood something that still holds true today: the interests of science are often at cross-purposes to the pursuit of geographical discovery (Robinson 2006). In Peary’s case, this meant that he had to look outside of the Federal government for support, raising money from private donors and members of the public. These groups accepted the symbolic, visionary power of the "Attainment of the Pole" despite the fact that Peary’s expedition planned to do little else at 90˚N that was scientific or practical. It was not a plan without risks. Science carried credibility – then as now – and it helped give status to earlier expeditions in the 1800s. Yet Peary sailed north nevertheless. He returned with little to show for his exploits but a series of photographs of the polar world. The photos almost always shows Peary or a member of his party in the foreground of the polar landscape. He knew that photos needed a human figure to serve as the viewer’s proxy. The same holds true today. The value of human explorers lies in who they are rather than what they can do: to watch an astronaut walk through the red dust of Mars is imagine ourselves there.