The human exploration of Mars will be an enterprise that confirms the potential for humans to leave their home planet and make their way outward into the cosmos. Though just a small step on a cosmic scale, it will be a significant one for humans, because it will require going away from Earth with very limited capability to return. Once committed to a journey to Mars, astronauts will not be able to return until the alignment of the planets allows their return. This is the most radical difference between this exploration and all previous explorations. There is a very narrow window within which return is possible, and the commitment to launch is a commitment to three years in space.
Mars is an intriguing and exciting planet, and there are many adventures and findings that await explorers. We must prepare for these before we go, providing the tools that the explorers will use, anticipating as much as possible the situations they will encounter and preparing them for the unexpected. For the first time in a space exploration mission, it will be up to the crew to solve their own emergency problems. At the distance of Mars from the Earth, it can be as much as 40 minutes from the time a message goes out from Earth to the time an answer is received back on Earth. The crews and their systems must be able to accomplish their objectives in a highly autonomous manner.
Exploration Program Objectives
Mars is an intriguing planet, for what it can tell us about the origin and history of planets and of life. Visible to the ancients, and distinctly reddish in the night sky, the next planet has always been an attractive subject for imaginative science fiction. As the capability for space exploration grew in the 1960's, it became clear that Mars is not, like Earth, a planet teeming with life, and is now a hostile environment for humans. The images of Mariner 4 showed a Moon-like terrain, dominated by large impact craters. This terrain now is believed to an represent ancient crust, similar to the Moon's, formed in an initial period of planetary differentiation. Mariner 9 showed for the first time that Mars was not totally Moon-like, but exhibits later volcanic and tectonic features. Large volcanos of relatively recent activity and large crustal rifts due to tensional forces demonstrate the working of internal forces. The absolute time scale is not accurately calibrated, however, by analogy with the Moon, the initial crustal formation may have occurred between 4 billion and 4.5 billion years ago, and the apparent freshness of the large martian volcanos suggests their formation within the last billion years.
Mars' atmosphere consists largely of carbon dioxide, with a typical surface pressure of about .01 Earth atmospheres, and surface temperatures that may reach 25 C on the equator in mid-summer, but are generally much colder. At these pressures and temperatures, water can not exist in liquid form on the surface. However, Mariner 9 and the subsequent Viking missions observed features which indicate that liquid water has been present on Mars' surface in past epochs. Evidence of both running water and standing water has been noted. The interpretation is that the atmosphere of Mars was thicker and warmer in former times, and perhaps much like the Earth's early atmosphere before the appearance of oxygen. Three questions arise: (a) What was the reason for the change of atmospheric conditions on Mars? (b) What are the implications of such changes for environmental changes on Earth?; and (c) Is it possible that life arose in the early Earth-like history of Mars (and, if it arose, can it still be found somewhere on Mars)?
These three scientific questions are at the core of the Mars scientific exploration defined by the Reference Mission. They can all be addressed principally by understanding the geological characteristics of the planet - the types of rocks present, their absolute and relative ages, the distribution of subsurface water, the history of volcanic activity, the distribution of life-forming elements and compounds, and others. These attributes all have to be understood in the context of what we know about the Earth, Moon and other bodies of our solar system.
2. Human Expansion
The dream of human exploration of Mars is intimately tied to the belief that new lands create new opportunities. In human history, migrations of people have been stimulated by overcrowding, exhaustion of resources, the search for religious or economic freedom, competitive advantage, and other human concerns. Rarely have humans entered new territory, then completely abandoned it. In the past, there have always been a few people who were adventurous enough to adopt a newly-found territory as their home. Most of these settlements have eventually become economically self-sufficient, and have enlarged the genetic and economic diversity of humanity. The technological revolution of the 20th Century, with high speed communication and transportation and integrated economic activity, has reversed the trend toward human diversity; however, settlement of the planets can once again enlarge the sphere of human action and life.
The settlement of Mars presents new problems and challenges. Principal among these is the absence of a livable natural environment. That, and the current high cost of transportation are the main barriers to human expansion there. The fact that humans, once on Mars, can not easily return to the Earth, and then only at specified times approximately 26 months apart, makes it necessary to develop systems with high reliability and robustness. The creation of a livable, artificial environment, is technically feasible. The high cost of transportation will ultimately be reduced. The Reference Mission is not a program to settle Mars; however, the objectives of the Reference Mission are to establish the feasibility of and the technological basis for human settlement of the planet.
3. International Cooperation
The space age gained its start in a period of intense technical and social competition between east and west, represented by the Soviet Union and the United States. Competition during the International Geophysical Year resulted in the Soviet Union being the first to launch a satellite into Earth orbit, and served as a challenge and reminder to the United States that technological supremecy was not solely the province of the United States. The start of the Apollo program was a political decision based more on the perception of the political and technological rewards to be gained by attacking a truly difficult objective in a constrained time period. The space race began, the United States won it, and a few years later, the Soviet Union had collapsed.
Fortunately, the Russians did not view the Apollo success as a reason to terminate their program, and they continued to develop capabilities that are fully on a par with United States capabilities in many areas. Also, during the post-Apollo time frame, space capability grew in Europe, with the formation of the European Space Agency, in Japan, China and other countries.
The basis has been laid for a truly international approach to Mars exploration. The exploration of Mars should be an international enterprise.
It would exhibit a great vanity for any country to undertake human exploration of Mars alone, particularly when others, who may not now have the required magnitude of capability or financial resources, do have the underlying technological knowhow. Mars should be an objective in which all humanity can share. An underlying requirement for the Reference Mission is that it be implemented by a multinational group of nations and explorers.