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Space Studies Board Annual Report 2007 (2008) / Chapter Skim
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5.9 The Limits of Organic Life in Planetary Systems
Pages 94-96

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From page 94...
... The canonical characteristics of life are inherent capacities to adapt to changing environmental conditions and to increase in complexity by multiple mechanisms, particularly by interactions with other living organisms. One of the apparent generalizations that can be drawn from knowledge of Earth life is that lateral gene transfer is an ancient and efficient mechanism for rapidly creating diversity and complexity.
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From page 95...
... Finally, the committee considered more exotic solutions to problems that must be solved to create the emergent properties that we agree characterize life. The committee found that using thermal and chemical energy to maintain thermodynamic disequilibria, covalent bonds between carbon atoms, water as the liquid, and DNA as a molecular system to support Darwinian evolution is not the only way to create phenomena that would be recognized as life.
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From page 96...
... Recommendation 2. The National Aeronautics and Space Administration and the National Science Foundation should support these kinds of field research: • A search for remnants of an RNA world in extant extremophiles that are deeply rooted in the phylogenetic tree of life; • A search for organisms with novel metabolic and bioenergetic pathways, particularly pathways involved in carbon dioxide and carbon monoxide reduction and methane oxidation coupled with electron acceptors other than oxygen; • A search for organisms that derive some of their catalytic activity from minerals rather than protein enzymes; • A search for organisms from environments that are limited in key nutrients, including phosphorus and iron, and determination of whether they can substitute other elements, such as arsenic, for phosphorus; • A search for life that can extract essential nutrients -- such as phosphorus, iron, and other metals -- from rocks, such as pyrites and apatite; • A search for anomalous gene sequences in conserved genes, particularly DNA- and RNA-modifying genes; • Study of the resistance of microorganisms that form biofilms on minerals to the harsh conditions of interplanetary transport; and • A search for life that stores its heredity in chemicals other than nucleic acids.
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Key Terms

  • terran life
  • covalent bonds
  • thermodynamic disequilibria
  • organic life
  • support darwinian

  • chemical energy
  • organic materials
  • chemical structures
  • maintain thermodynamic
  • committee asked

  • unstable environmental
  • permit returning
  • potential metabolic
  • emerging field
  • terran environments

  • living organisms
  • create phenomena
  • minerals set
  • efficient mechanism
  • active water

  • detect lighter
  • water geysers
  • liquid cryosolvents
  • available thermodynamic
  • electron acceptors

  • dynamic disequilibrium
  • understand interactions
  • alternative chemical
  • emergent properties
  • contemporary terran


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