Should a manned mission to Mars be attempted

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Should a manned mission to Mars be attempted?

Viewpoint: Yes, a manned mission to Mars is the next logical step for space exploration.

Viewpoint: No, a manned mission to Mars would be an enormously expensive enterprise with insufficient return to justify it.

Mars has long been an object of peculiar fascination. As one of the nearest worlds beyond Earth, it is naturally one of the most accessible for visitation by robot or manned spacecraft. Numerous unmanned missions have targeted the so-called Red Planet, from the Mariner and Viking spacecraft of the 1960s and 1970s to the more recent Mars Pathfinder, whose robot explorer Sojourner generated widespread public interest in 1997.

For more than a century, Mars also has been regarded as a likely—or at least possible—location of extraterrestrial life. In 1877 the Italian astronomer Giovanni Schiaparelli identified features on the Martian surface that he called canali (channels). While the intent was only to indicate the presence of channel-like markings on the surface, the English mistranslation of "canali" into "canal" implied intelligent origin. The U.S. mathematician Percival Lowell believed firmly in the existence of intelligent life on Mars, and spent years sketching the Martian surface from the observatory he founded in Flagstaff, Arizona, in the 1890s.

While Schiaparelli and Lowell carried out their systematic searches for Martian life, other imaginations were at work as well. H. G. Wells cemented the concept of extraterrestrials on Mars with his classic book War of the Worlds (1898), in which the Martians were portrayed as antisocial creatures intent on the subjugation of Earth. Hostile Martians soon emerged in movies and comic books.

The idea of Martians, especially unpleasant ones, worked its way deeply into the public psyche. In 1938 Orson Welles dramatized War of the Worlds, transferring it to New Jersey and reporting the Martian invasion over the radio as a real-time event. Citizens already jittery of the events unfolding in Europe panicked, convinced that Earth was actually under siege by aliens. As recently as 1996, the Hollywood movie Mars Attacks! satirically portrayed a U.S. president pleading, "Can't we all just get along?" and then being skewered by a bulbous-headed, glass-helmeted Martian.

Despite this popular imagery, no evidence of life on Mars has so far been discovered. The planet nevertheless remains an inviting next step for human exploration and, in the minds of visionaries, colonization. Mars is nearby, with a flight time of many months rather than many years. There is evidence that water stood on Mars's surface in the past, there is water ice in the polar caps, the temperatures are cold but not much colder than those in Earth's arctic regions, and there is at least a thin atmosphere. By contrast, the other nearby planets, Mercury and Venus, are unsuitable for a manned venture. Both are intolerably hot, and Venus is swathed in a thick atmosphere that creates crushing pressures at its surface.

For these practical reasons, as well as philosophical ones about human curiosity and our desire for challenge, many argue that Mars is a sensible place for humans to make their next great leap of exploration. The astronomer Carl Sagan argued eloquently for such an undertaking, commenting in his book Cosmos (1980) that perhaps Lowell was right after all: there are indeed Martians, and we are they.

Opponents to a manned mission to Mars believe that there are more effective ways to invest vast amounts of financial and technical resources. Manned space travel is hideously expensive; a manned mission to Mars would cost tens of billions of dollars by the most optimistic estimates. Given the penchant for ambitious space missions to substantially overrun their budgets, estimates approaching a half trillion dollars have been advanced. This staggering cost, say opponents, defeats all arguments about the spirit of exploration, spin-off technology, and the necessity of expanding to other worlds for the survival of humans as a species.

If we are to explore other worlds, opponents argue, we should use robotic spacecraft. Since they do not need to be designed to keep people alive inside them, they are much smaller and cheaper to construct than manned vessels. Robotic missions costing tens of millions of dollars—well under 1% of the cheapest proposed scenarios for manned Mars missions—can be flown quickly to their targets, capturing a wealth of data with the advanced imaging and data storage systems now available.

All of these arguments point out the central difficulty facing proponents of a manned Mars mission: An initial manned exploration of Mars would necessarily be a cursory first step into human interplanetary exploration. The objectives and returns of the mission would be relatively limited, yet the cost would remain huge. Arguments about the necessity of colonizing Mars for species survival, the potential for cultural development and improved international cooperation, acquisition of spin-off technology, and the development of resource-producing colonies are all visionary, long-term ideas.

In contrast, today's society demands a rapid return on investments. E-mail and the Internet provide means of widespread instant communication. Entertainment and commercials thrive on fast-moving images only seconds in duration. Budgets seem perennially insufficient, yet pressure to produce a result before the competitor is constant. Undeniably, the $20 billion to $500 billion spent on a manned Mars mission could be otherwise directed to projects with immediate benefits: technology, medical research, well-defined robotic missions of space exploration, and a host of other applications.

Cynics lament the putative greediness of the "me" generation, but paying attention to immediate needs has been a necessity for virtually all of human history. The technology that allows us to devote large resources to distant, egalitarian goals is still in its infancy; prior to the nineteenth century, life for most of humanity was merely survival. Indeed, for much of present-day humanity, it still is. Given these conditions, our tendency to address immediate goals is hardly unreasonable. However, it is possible at the beginning of the twenty-first century to at least contemplate longer-term objectives such as the colonization of another world. Decisions about where and how we allocate such long-term resources underlie the arguments that follow.

—JEFFREY HALL

Viewpoint: Yes, a manned mission to Mars is the next logical step for space exploration.

Mars Pioneers

History records that humans, by nature, are explorers. The reasons for exploring our solar system, presently and in the future, parallel the reasons that prompted pioneers to explore new lands on Earth. In sending a manned mission to Mars, our culture would be continuing a tradition that defines the human race. As a result of past explorations, people have gained enormous benefits. The exploration of our solar system began in earnest with the Apollo manned missions to the Moon from 1969 to 1972, and continued with robotic and satellite missions to all of the planets except for Pluto. Exploration of the solar system is a reality in the twenty-first century.

The Mars Society, whose purpose is to promote the exploration and settlement of Mars, advocates beginning the exploration of Mars for human colonization as soon as possible. Its members believe discovery missions can be completed inexpensively with existing technology, and produce enormous benefits. The successful exploration and colonization of Mars would show that humans have achieved greater maturity, proving that people are capable of developing colonies away from Earth in order to improve society and to safeguard the future.

The exploration of Mars gained even more attention in the late 1990s with the discovery of possible ancient life on Mars and the examination of the planet by the Mars Pathfinder. As scientific knowledge and technology continue to improve, especially with respect to exploration of the solar system, a stable foundation is being established to eventually set foot on Mars. The first manned mission to Mars would provide the initial contact that humans need to create a living community on the planet.

According to the Goddard Space Flight Center of the National Aeronautics and Space Administration (NASA), a manned mission to Mars lies "on the very edge of our technological ability." The accomplishment of such a goal would rapidly and dramatically increase our knowledge in numerous scientific and technological areas. For example, it would provide a more detailed understanding of Mars and, in turn, would provide a more complete understanding of the geologic processes and evolution of Earth. A manned Mars mission would answer many questions and increase the number of new questions that people seek to understand.

For too long people have believed that reaching Mars requires very complicated technologies, interplanetary spaceships only imagined in the minds of science-fiction writers, and budgets reaching a half trillion dollars. Contrary to these beliefs, it is possible to conduct a Mars mission using available technologies (or at least with modest advancements in such technologies) that have been developed since the early space missions of the 1960s and from resources available on Mars. According to James Hollingshead and Bo Maxwell of the Mars Society, "In the 1960s, America's economy was substantially boosted by spin-offs from the Apollo programme to reach the Moon." Hollingshead and Maxwell contend that similar benefits would result from spin-offs of Martian exploratory missions.

Why would humans go to Mars? To benefit humanity. The following discussion examines the most common technological, scientific, economic, and philosophical justifications for the exploration and colonization of Mars.

Technology and Science

Technological and scientific research and advancements are important reasons why a manned Mars mission should be attempted. The development of new and improved technologies for the mission would enhance the lives of those on Earth, and could include such innovations as more efficient propulsion systems for the transportation industry and better life-support systems in the medical community.

The expansion of our scientific knowledge also would increase from the exploration of Mars. This intriguing planet can tell us about the origin and history of our planet and other planets, and perhaps even about the creation of life on Earth. The atmosphere of Mars consists mostly of carbon dioxide, and possesses an average surface pressure of about 0.01 Earth atmospheres. While the surface temperature of Mars may reach a high of 77°F (25°C) on the equator, most of the time temperatures are much colder. The average temperature on Mars is about-67°F (-55°C). Recent evidence from the 1990s suggests that Mars contains water, the one key ingredient upon which any practical colonization effort would depend. In fact, based on a geophysical study by Dr. Laurie Leshin of Arizona State University, Martian water could be two to three times as abundant as previously believed. Because the pressure and temperatures are so low, water cannot exist in liquid form on the surface of Mars. Regardless of this, the Mariner 9 and Viking missions of the 1970s observed old surface features that indicate both running and standing water. Current understanding presumes that the Martian atmosphere was once thicker and warmer, even possibly similar to Earth's early atmosphere. Such characteristics found on Mars are key to understanding Earth's history and future.

Dr. Michael Duke of NASA's Johnson Space Center has indicated that a manned Mars mission would help to answer three important scientific questions: (1) What caused the change in atmospheric conditions of Mars? (2) What do these changes mean with respect to environmental changes that have occurred, and are presently occurring, on Earth? (3) Did life begin on Mars like it did on Earth; if so, can supporting evidence be found on Mars? A manned mission to Mars would produce a wealth of scientific information about issues people have pondered for years, and would in all likelihood increase the number of questions that have yet to be pondered.

Planetary Insurance

Dr. Richard Poss, a University of Arizona humanities professor, proposed a scenario of planetary insurance: if Earth were destroyed, western civilization would continue if Martian colonies already had been established. According to Dr. J. Richard Gott III, a Princeton University astrophysics professor, "We live on a small planet covered with the bones of extinct species, proving that such catastrophes do occur routinely." Gott believes, "Asteroids, comets, epidemics, climatological, or ecological catastrophes or even man-made disasters could do our species in. We need a life insurance policy to guarantee the survival of the human race." With all people on one planet, a catastrophe could theoretically wipe out all human life—or at least a majority of life, thereby eliminating the chances of recovery. With a new Mars colony away from Earth, humankind would have a better chance at long-term survival.

Cultural and Economic Evolution

Another important reason why a manned Mars mission should be attempted has been termed "cultural and economic evolution." Mars is the next logical step in the cultural evolution from Earth. A first mission, and eventually other missions, would bring colonists and supplies from Earth to Mars. Migrations of people in the past have eased overcrowding and the depletion of natural resources from the original homeland, thus improving economic conditions. These migrations have almost always concluded with a permanent settlement. More importantly, the newly settled establishments eventually have become economically self-sufficient, and have provided economic benefits back to the homeland. The settlement of Mars could begin the process of relieving population pressures on Earth.

A Martian colony also could provide a select few colonists with a territory that is not heavily laden with bureaucracy and frustrating regulations, and where people with innovative ideas could maximize their benefits. This viewpoint is a far-future ideal, but it is possible that Mars eventually could serve the same role in the twenty-first century that the United States did in the eighteenth century. Without anywhere to expand, there is a danger that society will stagnate. It is important for society to grow, and almost all progress is driven by that need. The exploration and settlement of the planet Mars could enable continued human development.

International Cooperation

A manned mission to Mars also should be attempted because it would help to bring about international cooperation. Such a mission would be a huge undertaking; it would be impossible for one country to provide all of the necessary financial support and technical know-how. An international Mars exploration effort has the potential to bring about a sense of global unity, with many nations cooperating to accomplish the mission.

Extraterrestrial Life

Is there life anywhere outside of Earth? This question has been asked for generations. There are many reasons to believe that Mars may once have held single-cell life. In the August 16, 1996, issue of Science, David McKay from the Johnson Space Center and other scientists announced the first identification of organic compounds in a Martian meteorite. The authors hypothesized that these compounds might show evidence of ancient Martian microorganisms. A less probable chance, but one that still exists, states that this life went beyond a single cell, and might continue to exist today. From a biological, philosophical, and theological point of view, discovering that life existed on Mars (or that life never existed) would make a profound statement to all of humankind.

Second-Best Planet upon Which to Live

The creation of a livable, artificial environment is technically feasible on Mars, and this planet is probably the most hospitable environment outside of Earth to adequately support a human presence. According to a 2001 Goddard Space Flight Center Web page on Mars, the planet is the "only real candidate for future human exploration and colonization." Mars offers the opportunity to use its own resources to provide air for explorers to breathe and fuel for their vehicles. Mars also has materials that are rare and expensive on Earth. For example, Mars has five times more deuterium than Earth. Deuterium may well be needed in future fusion power plants.

Comparing the other planets of the solar system also shows the advantages of exploring Mars. The planet Mercury is too close to the Sun (with extremes in temperatures and radiation) and contains almost no atmosphere. Venus is too hot (averaging 932°F [500°C]), with extreme surface pressures. The gas giants (Jupiter, Saturn, Uranus, and Neptune) do not provide a feasible landing surface. The moons of the gas planets are considered too far away to be a practical route for initial colonization of the solar system and are much more inhospitable than Mars. The outer planet Pluto is too far away, and too cold for easy colonization. The Moon is the only other likely body for human colonization. It has two problems that would limit its effectiveness: (1) the lunar day is about 29 Earth days in length, making it difficult for plants to survive, and (2) the Moon lacks an atmosphere, eliminating the necessary human radiation shield. Mars is the only place in the solar system where plants can grow with no artificial illumination and no massive radiation shielding. Mars also likely possesses large quantities of water that would help for exploration, base building, settlement, and terraforming.

Comparative Planetology

Another reason for a manned Mars mission is comparative planetology: by better understanding Mars and its evolution, a better understanding of Earth would be achieved. Unmanned Mars rovers can only conduct a limited amount of research. With requirements to travel long distances across rough terrain, climb steep slopes, and perform heavy lifting, a crewed presence is necessary, and is well beyond the abilities of robots.

Future Investment

Investment in a manned Mars mission is reasonable when compared with the costs of current Earth projects. Potential monetary returns are high when compared to the investment costs. In addition, people thrive on a challenge. Between 1961 and 1972, with the Moon landing as the goal, NASA scientists and technicians produced technological innovations at a rate several orders of magnitude greater than the agency has shown since. Even so, NASA's average budget in the late 1960s (in real dollars) was only 20% more than it was in the late 1990s ($16 billion 1998 dollars compared with $13 billion). Because NASA had a goal it was forced to create new technologies and to "think outside the box." The challenge of a manned Mars mission is the same: to give the United States, and the world, a real return for its space dollars.

Inspiration

Dr. Robert Zubrin, a Colorado astronautical engineer and the president of the International Mars Society, stated in a 2001 interview, "I believe civilizations are like people. We grow when we're challenged. Youth deserve challenge. They require it. They thrive on it. Out of that challenge we would get millions of new scientists, inventors, doctors, medical researchers."

Another reason for a manned Mars mission is to inspire. The first manned Mars landing would serve as an inspiration for the world's children. About 100 million U.S. children will be in school during the next 10 years. If only 1% were inspired to pursue scientific and engineering educations, an additional one million more scientists, engineers, technicians, and doctors would be produced. With one million more professionals we would produce a higher-educated populace. This would help to assure a more prosperous future for the human race.

Conclusion

In 2001 then-NASA administrator Daniel Goldin said that the first Mars landing was expected between 10 and 20 years in the future. At the beginning of the twenty-first century, many pro-Mars groups are actively lobbying the U.S. Congress and the president to launch such a manned program. It would create thousands of new jobs, spur technological innovation and new inventions, excite children around the world to study science and math, and unite our society as a spacefaring civilization.

—WILLIAM ARTHUR ATKINS

Viewpoint: No, a manned mission to Mars would be an enormously expensive enterprise with insufficient return to justify it.

For some time now there have been calls from a variety of people and organizations for a manned mission to the planet Mars. According to a report from the National Science Foundation released in June 2000, there is solid public support for such an endeavor. Myriad benefits have been predicted to follow from the human exploration, and possible habitation, of the Red Planet. A manned mission to Mars, however, cannot be considered in a vacuum. Such a mission would require a considerable commitment of financial resources over an extended period of time—resources that would not be available for other projects on Earth or in space.

Cost-versus-Benefit Analysis for a Manned Mars Mission

Because of the huge costs associated with a manned trip to Mars, at least with the technology and infrastructure currently available, any such mission would be a national or probably international endeavor. Whenever taxpayers' money is used to fund a project as costly and risky as a manned mission to Mars, people have a right to be presented with a convincing argument for the project: a cost-versus-benefit analysis for a manned Mars mission must be presented to the public. Do the projected benefits from such a mission overwhelmingly justify the large financial costs, as well as the inherent risks, that would be encountered?Some of the most vociferous advocates for a manned mission to Mars claim that a cascade of benefits would sooner or later follow such a pioneering effort, especially if the exploratory mission(s) resulted in the human colonization of Mars. As discussed in greater detail later in this essay, several of the most compelling benefits claimed by advocates are at best exaggerated, and at worst nothing more than wishful thinking and hype. This essay first examines the cost elements of the cost-versus-benefit analysis of sending people to Mars.

Projected Mission Costs

Many studies and analyses have been performed to determine the cost of a manned trip to Mars. These studies have been heavily influenced by the mission parameters that go into planning such a trip: the number of crew members traveling to Mars, types of launch and landing vehicles used, and duration of the crew's stay before returning to Earth. Cost estimates range from as low as $20 billion for the Mars Direct plan touted by Robert Zubrin, the president of the International Mars Society, to as much as $450 billion according to a 1990 National Aeronautics and Space Administration (NASA) report. As calculating the cost of a manned mission to Mars is heavily dependent upon the organization or people creating the analysis, where can one look for guidance regarding the accuracy of various estimates? A reasonable analysis of these disparate estimates should include an historical review of recent manned space programs. The most recent, similar project is the International Space Station ( ISS ) program, which involves many countries but is led principally by the United States, which pays about three-quarters of the program's costs. The ISS is the best indicator of what an internationally led Mars program would entail, because the two endeavors share several key characteristics; most notably, they are both long-duration space missions involving humans and are dependent upon an international consortium for funding and hardware.

ISS as an Historical Guide

The ISS had its genesis in a proposal made by President Ronald Reagan in his 1984 State of the Union message to construct a permanently crewed space station in low-Earth orbit (a few hundred miles above Earth's surface). Authorized by Congress that same year, the space station was to be completed by 1994 and was to cost approximately $8 billion according to NASA. Since 1984 the space station program has repeatedly been modified and delayed. As a result, according to the U.S. General Accounting Office (GAO), by 1993 $11.4 billion had been spent on the space station program, with not a single piece of space hardware in orbit to show for the money spent. The program eventually became international, even incorporating former U.S. competitors in space such as Russia. Overall, the space station program (renamed the ISS ) has a nearly 20-year track record of being both grossly over budget and behind schedule. The latest estimates from NASA delay the completion of the ISS until 2004 at the earliest. In recent years, according to the GAO, NASA has dramatically underestimated ISS operational costs on the order of $2.5 billion per year by omitting expenditures such as space shuttle flights flown in support of the ISS. The GAO has predicted that the ISS eventually will incur a total cost of around $100 billion. Even taking inflation into account, the original estimate of $8 billion for a space station now appears woefully optimistic. An international manned mission to Mars might well become—despite the protestations of its advocates—another fiscal disaster like the ISS.

Some might argue that the ISS is not a good model for predicting how a manned Mars project might fare. For example, due to the project's changing political goals, the ISS went through many modifications that often did more harm than good. Specifically, the decision to allow Russian participation in the ISS project resulted in disastrous fiscal and scheduling problems, which in turn were a symptom of Russia's economic and political woes. But if the international effort to construct a space station in low-Earth orbit has encountered such enormous difficulties, why should the public believe that an international project to reach another world millions of miles away can avoid becoming mired in the same sort of endless delays and cost overruns? The prudent answer would seem to be that any notions of a manned Mars mission should be laid aside altogether. At the very least, an expedition to Mars should be postponed until NASA and its international partners can bring the ISS to fruition and then operate the ISS program safely and on budget over a period of many years. NASA would thereby demonstrate that it could, at least in some instances, deliver on what it promises in the way of costs and schedules.

Many space researchers and scientists believe the vast financial resources gobbled up by the ISS could have been much better spent by funding a host of robotic exploratory missions. In the March 2001 issue of Policy Options, the project management consultant Denis Legacey noted, "For the tens of billions of dollars it [the United States] spends on the ISS, it spends only hundreds of millions on space exploration." Undoubtedly, a manned Mars mission would have a similar limiting effect on robotic missions of the future.

Alleged Benefits of a Manned Mars Mission

Many significant benefits have been touted as the natural result of a mission to land people on Mars, including: major technological spin-offs; a unity of purpose and shared excitement for people throughout the world; and, if some cataclysm were to befall Earth, as a way to assure the preservation of humankind. However, these and other alleged benefits are only predictions that may or may not accrue from such a mission. As with the ISS program, all sorts of optimistic claims can be made that ultimately will fall far short of actual results. For example, advocates of a manned mission to Mars claim the effort would produce plentiful high-tech spin-offs that would benefit industry and improve life here on Earth. It is only reasonable to ask if the billions earmarked for a potential manned Mars mission would be better spent by directly funding government and industry research labs for the creation of new products and processes. Numerous research and political organizations outside of the space exploration community have suggested that several times more spin-offs and innovations could be achieved if the money were spent directly on research instead of on the space program.

Organizations that support a manned Mars mission, such as the International Mars Society, also have claimed that it should be the precursor to human settlement of Mars, which should be accomplished sooner rather than later because of several dire threats to the survival of the human race. The extinction of our species could come about either through man-made events (an allout nuclear war) or through a natural cataclysm. Mass extinctions of life on Earth have occurred repeatedly over the course of geologic time; indeed, some paleontologists claim mass extinctions have occurred on Earth once every 30 million years. In a 1984 paper, the paleontologists Dr. David Raup and Dr. J. John Sepkoski proposed a frequency of every 26 million years.Many events could make life on Earth difficult: the impact of a large comet or asteroid, for instance, or a series of massive volcanic eruptions. Zubrin and other advocates for the habitation of Mars say that in the case of such a cataclysmic event, a self-sustaining Martian colony would ensure the survival of the species. However, the probability of such a naturally occurring apocalyptic event happening in the next several hundred years is exceedingly tiny. Large comets or asteroids capable of destroying life on Earth strike our planet very infrequently. "Killer" asteroids on the order of 10 miles in diameter—about the size of the asteroid said to have wiped out the dinosaurs 65 million years ago—are believed to hit Earth only once every 100 million years.

Even assuming that preparations should be made to save the human race from possible extinction, a Mars colony would not necessarily be the best option. One alternative is using the myriad shelters (many of which are still in existence) that were constructed during the cold war in the latter half of the twentieth century. These shelters are located in many different countries and were designed to protect a limited number of people from the disastrous effects of a nuclear war. If the goal is the survival of humanity, such shelters could be stockpiled with food and fuel to keep a select group of people alive for years after a natural catastrophe, until the worst effects have subsided. Another alternative to a Mars colony is a self-sustaining Moon base, which appears more feasible because of evidence from NASA's 1998 Lunar Prospector data indicating water ice trapped near the lunar poles. Earth shelters and a lunar colony both present cheaper alternatives to the massive investment and complexity integral to a permanent Mars colony. Moreover, either option could likely be achieved much more quickly than the colonization of Mars.

Alternatives to a Manned Mars Mission

Even by the most optimistic projections, a manned mission to Mars would cost tens of billions of dollars. Based on the excessive cost overruns and schedule delays of previous manned space programs, the total cost might well balloon into the hundreds of billions of dollars. This money would not be available to fund other important space initiatives. In place of a people-to-Mars project, many scientists favor an extensive, but much less expensive, series of robotic missions to explore the solar system. Recent advances in robotics and intelligent processing systems make that choice even more viable.

The existing over-budget and behind-schedule space station project must be brought to fruition before another large manned mission is attempted. If and when that day comes, a return trip to the Moon should be the first priority. The Moon is much closer to Earth than Mars, which means fewer onboard supplies and less fuel can be used to get to the Moon. A trip to the Moon would take days (as in the case of the Apollo missions), whereas most Mars proposals envision a trip lasting about six months. The long duration of a Mars voyage would mean much more radiation exposure for the crew (unless extensive shielding were used, which would add weight and cost to the spacecraft) than would be encountered on a lunar trip. A major argument for a Mars base over that of a lunar one is the presence of water on Mars. While early measurements of the lunar surface showed a complete absence of water, tantalizing evidence from the late 1990s indicated the possibility of water ice near the lunar poles, thus possibly eliminating a strong feature favoring Mars for colonization. In short, sending people to the Moon would be safer and cheaper than a similar manned mission to Mars, while still embodying many of its benefits, including providing a haven to guarantee human survival, creating technological spin-offs, and generating worldwide public attention and excitement.

Conclusion

A manned mission to Mars is an idea whose time definitely has not come, and should be deferred indefinitely. A variety of factors argues against putting people on Mars in the foreseeable future. For any publicly funded endeavor, the benefits obtained from the project must be weighed against the projected costs. As detailed earlier in this article, many of the benefits touted by advocates of a manned expedition to Mars are questionable, and could be achieved more safely and economically by a similar lunar expedition. The costs of a manned Mars mission also deserve scrutiny. Large, international space projects can consume many times the originally projected funds, as the financial quagmire of the ISS amply demonstrates. Moreover, the money tied up in a Mars expedition would not be available for other space projects—projects that would most likely produce far more return on their investment than a Mars endeavor. Myriad robotic missions to the solar system and beyond could be funded for a fraction of the cost of a Mars expedition. Developing additional manned space stations or a lunar colony would be far less expensive, as well as safer, than initiating a human mission to Mars.

—PHILIP KOTH

KEY TERMS

DEUTERIUM:

A heavy hydrogen isotope with one proton and one neutron.

PLANETOLOGY:

A branch of astronomy that studies the origin and composition of the planets and other condensed bodies in the solar system such as comets and meteors.

SPACE STATION:

Any facility that allows humans to live in space for extended periods of time.

SUPERNOVA:

A rare celestial phenomenon involving the expulsion of most of the material in a star, resulting in a luminous power output that can reach billions of times that of the Sun.

TERRAFORMING:

The process of transforming a given environment to make it more like Earth.

FOCUS ON ALH 84001 METEORITE

ALH 84001 is a meteorite (any metallic or stony material that survives flight through the atmosphere and lands on Earth). It was discovered in Allan Hills (for which it was named), Far Western Icefield, Antarctica, on December 27, 1984, by the National Science Foundation's ANSMET (ANtarctic Search for METeorites) expedition. It is estimated that ALH 84001 landed on Earth about 13,000 years ago. At the time of discovery ALH 84001 was shaped like a large potato and weighed about 4.25 lb (1.93 kg).

ALH 84001 is important to current and future explorations of Mars because it is believed that the meteorite originated from molten lava about 4.5 billion years ago on an ancient Martian volcano. Scientists believe that ALH 84001 could only have originated from Mars because of the trace gases it contains. The composition of the atmosphere of Mars was verified from analyses performed by the Viking lander spacecraft in 1976. The Martian atmosphere is unique in the solar system; its composition mostly consists of carbon dioxide, but also includes the elements nitrogen, argon, krypton, and xenon. The Viking landers also found that the atmosphere of Mars has an unusual relative abundance of the particular isotope nitrogen 15, and lesser relative abundances of the two isotopes argon 40 and xenon 129. Those same isotopic relative abundances are found in ALH 84001, which strongly supports its Martian origin. In addition, telescopic observation from Earth shows that the Martian atmosphere is very rich in deuterium (heavy hydrogen), as is ALH 84001.

—William Arthur Atkins

Science in Dispute