Foremost among these questions is the possibility of the existence of extraterrestrial life. The field which is concerned with the search for extraterrestrial life has come to be called "exobiology." In addition to the challenge of great technological problems which must be solved, exobiology is so closely related to the central scientific questions in biological science that it is considered by some to be the most significant pursuit in all of science. One of the major opportunities already presented by the advances in propulsion systems is the ability to escape from the influence of the Earth, which has made possible the study of organism-environment relationships, particularly the role that environmental stimuli play in the establishment and maintenance of normal organization in living systems. Transcending even these formidable objectives of space bioscience is an objective shared by all life sciences, the discovery of nature’s scheme for coding the messages contained in biological molecules. Extraterrestrial biology seeks to find not only evidence of life now present, but the vestigial chemicals of its previous existence. The ways and means have already been made available to study molecules on whose long, recorded messages is written the autobiography of evolution—the history of living organisms extending back to the beginnings of life. On this same basis, it is now within the realm of science to foresee the means of predicting the development of life from primordial, nonliving chemical systems. Closely allied to the search for extraterrestrial life is research which seeks to identify the materials and the conditions which are the prerequisites of life. Space bioscience research is now extending human knowledge of fundamental biological phenomena, both in space and on Earth, just as the physical sciences explore other aspects of the universe. The accomplishment of bioscience objectives is totally dependent upon advances in the technology of space flight. A highly developed launch-vehicle capability is essential to accomplish the long-duration missions required in the search for extraterrestrial life.