...the goal of planet colonization has been challenged by a radically different notion of the Final Frontier Created by Princeton professor of physics Gerard K.O'Neill, this new concept is based on one of those revolutionary propositions that are so simple they seem self-evident. The surface of a planet, O'Neill asserts, is not a very good place to house a post industrial society. Free space itself, he says, ist he natural ecological habitat for a high energy, high-growth technological species.

The best single presentation of O'Neill's Ideas is found in his book The High Frontier (William Morrow, 1976):"On a planetary surface," he argues, "we are the 'gravitationally disadvantaged,' at the bottom of a deep hole in potential energy. To raise ourselves from earth into free space is equivalent in energy to climbing out of a hole 6461 kilometers deep, a distance more than 600 times the height of Mt. Everest. Does it make sense to climb with great energy out of one such hole, drift across a region rich in energy and materials, and then laboriously climb back down into another hole, where both energy and matter are more difficult to get and to "use?" Answering with a resounding no, O'Neill explains how we could build a variety of space habitats, spacetowns, and eventually space cities,starting in the L-5 area (the most stable of the five Legrange points where the earth-moon gravitational fields balance out to zero.) Dr.O'Neill writes in ane asy, nontechnical style and stresses, after demonstrating the engineering soundness of his designs, that the resources and enormous new energy such space habitats would capture would stave off the Doomsday and New Dark Ages predicted by the professional pessimists of the Club of Rome and the pop ecology movement.

In a dispassionate comparison of the relative values of human and robotic spaceflight, the only surviving motivation for continuing human spaceflight is the ideology of adventure. But only a tiny number of Earth's six billion inhabitants are direct participants. For the rest of us, the adventure is vicarious and akin to that of watching a science fiction movie. At the end of the day, I ask myself whether the huge national commitment of technical talent to human spaceflight and the ever-present potential for the loss of precious human life are really justifiable.

Perhaps what we should do is genetically engineer new forms of Intelligent life that can survive the stress of space yet still conduct scientific experiments. Actually, such creatures have already been made in the lab. They're called robots. You don't have to feed them, they don't need life support, and they won't get upset if you don't bring them back to Earth. People, on the other hand, generally want to breathe, eat, and eventually come home.

It's probably true that no city has ever held a parade for a robot. But it's probably also true that no city has ever held a parade for an astronaut who wasn't the first (or last) to do something or go somewhere. Can n you name the two Apollo 12 or Apollo 16 astronauts who walked on the Moon? Probably not. Apollo 12 was the second lunar mission. Apollo 16 was^as the second-to-last. But I'll bet you have a favorite picture of the cosmos taken by the orbiting robot known as the Hubble Space Telescope. I'll bet you can recall images from the rovers that have six-wheeled their way across the rocky Martian landscape. I'll further bet that you've seen some jaw-dropping images of the Jovian planets—the gas giants of the outer solar system—and their zoo of moons, images taken over the decades by the Voyager, Galileo, and Cassini space probes.

The success of Apollo was mainly due to the fact that the project was conceived and honestly presented to the public as an international sporting event and not as a contribution to science. The order of priorities in Apollo was accurately reflected by the first item to be unloaded after each landing on the Moon's surface, the television camera. The landing, the coming and going of the astronauts, the exploring of the moon's surface, the gathering of Moon rocks and the earthward departure, all were expertly choreographed with the cameras placed in the right positions to make a dramatic show on television. This was to me the great surprise of the Apollo missions. There was nothing surprising in the fact that astronauts could walk on the Moon and bring home Moon rocks. There were no big scientific surprises in the chemistry of the Moon rocks or in the results of magnetic and seismic observations that the astronauts carried out. The big surprise was the quality of the public entertainment that the missions provided. I had never expected that we would see in real time astronauts hopping around in lunar gravity and driving their Rover down the Lincoln- Lee scarp to claim a lunar speed record of eleven miles per hour. Intensive television coverage was the driving force of Apollo. Von Braun had not imagined the possibilities of television when he decided that one kilohertz would be an adequate communication bandwidth for his Mars Project.

Pioneer 10 is the first interstellar spacecraft launched by mankind. It was also the fastest spacecraft launched, to the date of its departure. But it will take eighty thousand years for Pioneer 10 to reach the distance of the nearest star. Because space is so empty, it will never enter another Solar System. The little golden message aboard Pioneer 10 will be read, but only if there are interstellar voyagers able to detect and intercept Pioneer 10.

I believe that such an interception may occur, but by interstellar voyagers from the planet Earth, overtaking and heaving to this ancient space derelict – as if the Nina, with its crew jabbering in Castilian about falling off the edge of the world, were to be intercepted, somewhere off Tristan da Cunha, by the aircraft carrier John F. Kennedy.

The Solar System is much vaster than the Earth, but the speeds of our spacecraft are, of course, much greater than the speeds of the sailing ships of the fifteenth and sixteenth centuries. The spacecraft trip from the Earth to the Moon is faster than was the galleon trip from Spain to the Canary Islands. The voyage from Earth to Mars will take as long as did the sailing time from England to North America; the journey from Earth to the moons of Jupiter will require about the same time as did the voyage from France to Siam in the eighteenth century. Moreover, the fraction of the gross national product of the United States or the Soviet Union that is being expended even in the more costly manned space programs is just comparable to the fraction of the gross national product spent by England and France in the sixteenth and seventeenth centuries on their exploratory ventures by sailing ships. In economic terms and in human terms, we have performed such voyages before!

The Earth is overcrowded. Not yet in a literal sense: Our technology is adequate to maintain comfortably a population significantly larger than our present 3.6 billion. The Earth is overcrowded in a psychological sense. For that restless and ambition-driven fraction of mankind that has blazed new paths for our species, there are no new places to go. There are places inside of ourselves, but this is not the forte of such individuals. There are the ocean basins, but we are not yet committed to exploring them seriously; and when we do, they are likely to be exploited rapidly

At just this time in our history comes the possibility of exploring and colonizing our neighboring worlds in space. The opportunity has come to us not a moment too soon.

At the very beginning of the twentieth century competent scientific and lay opinion held that airplanes were impossible. The end of the century, barring the dark specter of nuclear or ecological catastrophes, will probably see joint Soviet and American manned space expeditions to the nearer planets.

This is the century in which some of the oldest dreams of Man have been realized, in which mankind has sprouted wings and realized the aspirations of Daedalus and da Vinci. Air-breathing, man-carrying machines now circumnavigate our planet in less than a day; other machines, skimming above the atmosphere, carry men around our globe in ninety minutes.

There is a generation of men and women for whom, in their youth, the planets were unimaginably distant points of light, and the Moon was the paradigm of the unattainable. Those same men and women, in middle life, have seen their fellows walk upon the surface of the Moon; in their old age, they will likely see men wandering along the dusty surface of Mars, their journeys illuminated by the battered face of Phobos. There is only one generation of humans in the tenmillion- year history of mankind that will live through such a transition. That generation is alive today

Because of their small sizes, Phobos and Deimos have very low gravitational accelerations. Their gravities do not pull very hard. The pull on Phobos is only about one one-thousandth of that on Earth. If you can perform a standing high jump of two or three feet on Earth, you could perform a standing high jump of half a mile on Phobos. It would not take many such jumps to circumnavigate Phobos. They would be graceful, slow, arcing leaps, taking many minutes to reach the high point of the self-propelled trajectory and then to return gently to the ground.

Even more interesting would be a game like baseball on Phobos. The velocity necessary to launch an object into orbit about Phobos is only about twenty miles per hour. An amateur baseball pitcher could easily launch a baseball into orbit around Phobos. The escape velocity from Phobos is only about thirty miles per hour, a speed easily reached by professional baseball pitchers. A baseball that had escaped from Phobos would still be in orbit about Mars – a man-launched moonlet. If Phobos were perfectly spherical, a lonely astronaut with an interest in baseball could invent a curious but somewhat sluggish version of this already rather sluggish game. First, as pitcher, he could throw the ball sidearm – at the horizon at between twenty and thirty miles per hour. He could then go home for lunch, because it will take about two hours for the baseball to circumnavigate Phobos. After lunch, he can pick up a bat, face the other direction and await his pitch of two hours earlier. Apart from the fact that good pitchers are seldom good hitters, hitting this pitch would be pretty easy: About fifteen seconds elapse from the appearance of the baseball at the horizon to its arrival in the vicinity of our astronaut. If he swings and misses – or, more likely, if the ball is wide of the plate – he can then go home for a two-hour nap, returning with his catcher's mitt to catch the ball. Alternatively, if he succeeds in hitting a fly ball at a velocity somewhere between twenty and thirty miles per hour, he can go home and take his nap, returning this time with a fielder's mitt, awaiting the return of the ball from the opposite horizon two hours later. Because Phobos is gravitationally lumpy, the game would be more difficult than I have indicated. Since daylight on Phobos lasts only about four hours, lights would have to be erected, or the game modified so that all pitching, hitting, and catching events happen on the day side.

These sports possibilities may, one day a century or two hence, provide a tourist industry for Phobos and Deimos. But baseball on Phobos is no more an argument for going there than, to take a random example, golf is for going to the Moon. The scientific interest in the moons of Mars – whether captured asteroids or debris from the formation of the planet – is, however, immense. Sooner or later, certainly on a time scale of centuries, there will be instruments – and then men – on the surface of Phobos looking up with awe at an immense red planet that fills the sky from zenith to horizon.

In all the history of mankind, there will be only one generation that will be first to explore the Solar System, one generation for which, in childhood, the planets are distant and indistinct discs moving through the night sky, and for which, in old age, the planets are places, diverse new worlds in the course of exploration.

There will be a time in our future history when the Solar System will be explored and inhabited. To them, and to all who come after us, the present moment will be a pivotal instant in the history of mankind. There are not many generations given an opportunity as historically significant as this one. The opportunity is ours, if we but grasp it. To paraphrase K. E. Tsiolkovsky, the founder of astronautics: The Earth is the cradle of mankind, but one cannot live in the cradle forever.

A human infant begins to achieve maturity by the experimental discovery that he is not the whole of the universe. The same is true of societies engaged in the exploration of their surroundings. The perspective carried by space exploration may hasten the maturation of mankind – a maturation that cannot come too soon.