MARS NEEDS HUMANS (c) Robert Zubrin & Chris McKay The purpose for sending humans to Mars is not to set altitude records for the aviation almanacs. Rather it is to resolve some of the most important questions concerning the role of life in the universe. Evidence available from the Mariner and Viking orbiters, including photographs of dry riverbeds, strongly indicate that Mars was once a warm and wet planet, and was so for a longer period of time than the several hundred millions years it took life to originate on Earth. Today Mars is cold and arid, with a surface environment hostile to terrestrial life forms. Nevertheless the question remains: since conditions on Earth and Mars were similar during the period that life originated on Earth, did life also evolve on Mars? The answer to this question is fundamental to understanding humanities place in the Universe. If we find evidence of life on Mars, however humble or long extinct, it would tell us the origin of life on Earth was not a result of freak chance. Instead, it would confirm our present speculations that life is a natural and emergent phenomenon of energy-rich, liquid water environments. It would imply that elsewhere in the galaxy there must almost certainly be a spectacular variety of other planets with liquid water and with life, and that the universe we inhabit is filled with living things whose diversity must surpass imagination. We would know we are not alone. The discovery of actual living organisms on Mars could be epochal in a practical sense as well. To date, we have had only terrestrial life forms to study, all possibly descendants of a common line, so that our understanding of biology is quite limited. Our position is like that of a person who is trying to understand the nature of language, but who is only acquainted with his or her mother tongue. Comparing Martian life forms with terrestrial ones would allow us to begin to determine which features of life on Earth are incidental and which are fundamental to the true nature of life itself. Such knowledge could lead to astounding breakthroughs in the biological sciences and medicine, resulting in dramatic improvements in the human condition. The search for evidence of life on Mars will not be an easy task. Consider how difficult it is to find fossils on Earth of such common megafauna as dinosaurs. Its going to be a lot harder to find fossils of microorganisms tend to be considerably smaller than dinosaurs and leave fossils that are much less obvious. For another, the Martian fossils are likely to be much older, and therefore rarer. Since the Martian environment is nowhere near as well understood as that of the Earth, the processes likely to lead to preservation are less well known. This will make it harder to locate sites where fossils would be preserved and more difficult to understand the unusual settings that resulted in preservation. On Earth the only way we know how to conduct such searches is with trained field scientists. Trained not only with classroom knowledge but with hands-on field experience, often over many years. While robotic probes operating from orbit or dispersed landing sites can provide essential preliminary data, they are simply incapable of conducting this type of exploration of Mars. Consider the probability of success of a program searching for dinosaur fossils on Earth conducted by random parachuting down small packages of instruments. The result would likely be nil. The same can be said with even greater certitude of a purely robotic search for the remains of life on Mars. If we want to solve the mystery of Mars' past or present life, trained field scientists working on the planet's surface for many years will be necessary to do the job. In addition to human intelligence and time on the surface, the third key element to explore Mars is mobility. Mars is a very big place, with a surface area equal to all Earth's land masses combined. Sites of scientific interest are likely to be far apart. The number of such sites that can be visited by a given expedition will increase in proportion to the square of the sortie range of the available surface transportation. Further more, to conduct thorough investigation of a geologic feature on Mars will require that studied can be performed at sites that span the feature under consideration. For example, to determine the timing and cause of fluvial erosion features at the terminus of the Valles Marineris canyon system may require that field sites at locations along the entire valley system - a distance of several thousand kilometers- be explored. It may not be necessary to cover this distance in a single traverse, but the ability to go repeatedly to sites and conduct intensive field studies over these distances is clearly indicated. Here again we see the adoption of a "dogsled" approach to Mars exploration is essential, since only the production of propellants out of local resources can enable the use of high powered ground rovers and ballistic flight vehicles necessary to provide explorers with the extensive mobility they will need. The top priority for the first Mars explorers will be to resolve the questions concerning the possible existence and nature of the planet's past or present life. But, however the answers to those questions turn out, over time new questions will move to the fore: Will there be life on Mars? That is, can humans settle Mars? Can we take a dead or nearly dead planet and turn it into a new home for civilization? Can we bring the planet to life?