EXOBIOLOGY

A Program of NASA's Solar System Exploration Division

Written by NASA Exobiology Program Manager: Michael A. Meyer

The principal goal of research in the area of the cosmic evolution of the biogenic compounds is to determine the history of the biogenic elements (C, H, N, O, P, S) from their birth in stars to their incorporation into planetary bodies. Six stages in this history have been defined for study: 1) nucleo-synthesis and ejection into the interstellar medium, 2) chemical evolution in the interstellar medium, 3) protostellar collapse, 4) chemical evolution in the solar nebula, 5) growth of planetesimals from dust, and 6) accumulation and thermal processing of planetoids. Potential missions associated with this area include the comet missions, a space station cosmic dust collector and the use of airborne and orbital observatories such as the Kuiper Airborne Observatory and the Space Infrared Telescope Facility (SIRTF).

Research in the area of prebiotic evolution seeks to understand the pathways and processes leading from the origin of a planet to the origin of life. The strategy is to investigate the planetary and molecular processes that set the physical and chemical conditions within which living systems arose. Four major objectives are to: 1) determine constraints on prebiotic evolution imposed by the physical and chemical histories of planets; 2) develop models of active boundary regions in which chemical evolution could have occurred; 3) determine what chemical systems could have served as precursors of metabolic and replicating systems both on Earth and elsewhere; and 4) determine in what forms prebiotic organic matter has been preserved in planetary materials. Potential missions include the Cassini mission to Titan, and future Mars mission opportunities such as Mars Pathfinder, the Mars Global Surveyor and follow-on missions.

The goal of research into the early evolution of life is to determine the nature of the most primitive organisms, the environment in which they evolved, and the way in which they influenced that environment. As an approach to understanding life in the universe, the opportunity is taken to investigate two natural repositories of evolutionary history available on Earth: the molecular record in living organisms and the geological record in rocks. These paired records are used to 1) determine when and in what setting life first appeared, 2) determine the characteristics of the first successful living organisms, 3) understand the phylogeny and physiology of microorganisms that inhabit hydrothermal areas now thought to be analogs of primitive environments, 4) determine the original nature of biotic energy transduction, membrane function, and information processing through study of extant microbes, and 5) elucidate the physical, chemical, and biotic forces operating on microbial evolution. Potential mission The research associated with the study of the evolution of advanced life seeks to determine the extrinsic factors influencing the development of advanced life and its potential distribution. This research includes an evaluation of the influence of extraterrestrial and planetary processes on the appearance and evolution of multicellular life, conducted by 1) tracing the effects of major changes in the Earth's environment on the evolution of complex life, especially during mass extinction events, and 2) determining the effects of global events and events originating in space on the production of environmental changes that affected the evolution of multicellular life. Also studies will be considered that would seek approaches to investigations furthering our understanding of the distribution of life elsewhere in the universe. Potential NASA missions include missions related to the study of extrasolar planets.