4. Energy Sources and Life
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An external energy source is a necessary condition for life, because living systems require a flow of energy to organize materials and maintain a low state of entropy (Morowitz 1968). Energy is also needed to perform work. Life on Earth can be distinguished by the external energy source that it uses. Autotrophic life derives energy from either sunlight or redox-reactions involving abiological compounds, while heterotrophic life uses high-energy organic molecules produced by autotrophic life as a source of energy. On other worlds, where other forms of energy may be more abundant, or where the primary sources for energy on Earth may be lacking, life may have evolved to depend on different forms of energy. In this chapter, we critically analyze the various forms of energy that are potentially available to living systems, consider other factors that bear on the evolution of energy-harvesting mechanisms, and evaluate the apparent availability of different forms of energy at different sites in our solar system.
KeywordsSolar System Hair Cell Lorentz Force Hydrothermal Vent Ocean Bottom
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