Chapter 6-1

A Universe of Life

Planets seem to be reasonable places for life. They are neither as hot and deadly as the surfaces of stars, nor as cold and empty as the space between them. The only life we know of in the universe has developed on a planet, the Earth. Thus, other planets have always been the major focus of our search for other forms of life. If planets are abundant in the universe, life may be common.

If planets are rare, we and our fellow Earthlings may be unique. Only thirty years ago, most astronomers believed that planetary systems were extremely rare. It was even thought that the solar system and the habitat that Earth provides might well be unique in the entire galaxy. At the same time almost nothing was known about the chemical basis for the origin of life. Since then, our view has changed drastically. Numerous studies have eroded the reasons why planetary systems and the development of life on suitable planets should be unlikely. Today, the leading theories for star formation suggest that planets may be the rule rather than the exception and that the formation of planets is expected to accompany the formation of stars. At the same time, new discoveries have shown that the chemicals necessary for life are abundant beyond the Earth. Inter stellar gas clouds have been found to contain biologically important organic molecules made of carbon, hydrogen, and other elements. Similar molecules have been detected in comets and meteorites. Therefore, today's theories suggest that life could be wide spread in the universe. Growing numbers of scientists are now convinced that extraterrestrial life must exist, and more and more people feel that contact with other civilizations is no longer something beyond our dreams but will be a natural event in the history of mankind.

The existence of extraterrestrial life and the origin of life are two questions that are intimately related. The major problem is the origin of life. This topic is intrinsically fascinating. It is surrounded by mystery, philosophy, and religion, and it has been the subject of contemplation and speculation since the beginning of human history. Only in the last century has the question become recognized as a subject suitable for direct scientific inquiry. Individual researchers and groups of scientists have considered the problem for years, but NASA was the first organization to provide a cohesive, interdisciplinary approach, combining the various scientific programs that had investigated the question since the early 1960s.

This integrated attack includes disciplines as diverse as astronomy, biology, chemistry, geology, and engineering. Ground-based laboratory research, astronomical observations, and space missions have all been brought to bear on the questions of the uniqueness of life on Earth, the origin of life in the universe, and the place of life in the general cosmology. We have come to the point that scientists can now devise experiments to answer such fundamental questions as: "Where did life come from?", "Why is life like it is?", "Are there other forms of life in the solar system or in the universe?", "Is there intelligent life elsewhere?"

This new science of exobiology has several goals. It seeks to understand the origin, evolution, and distribution of life and of the chemicals necessary for life, both on Earth and throughout the universe, and it seeks to determine the relationship of life to the evolution of planets. Through research in chemistry, geology, and biochemistry, and from our exploration of the planets, we have begun to pull together some parts of the origin-of-life puzzle. Pieces of the puzzle are being gathered from throughout the universe, from interplanetary and interstellar space, from other worlds, and naturally, from the Earth.

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