Cosmic Foundations of the Origin of Life

Cosmic Foundations of the Origin of Life - Cosmic...

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Cosmic foundations of the origin of life : Vali January-17-10 6:29 PM What is Life? Horowitz o Mutability o Self-duplication o Heterocatalysis o "life is synonymous with the possession of genetic properties. Any system with the capacity to mutate freely and to reproduce its mutation must almost inevitably evolve in direction that will ensure its preservation" Gatlin o Life has the "ability to store and process the information necessary for its own reproduction" Joyce (accepted as NASA's working definition of life) o "life is a self-sustained chemical system capable of undergoing Darwinian evolution" Altstein o "life is the process of existence of open non-equilibrium complete systems, which are composed of carbon-based polymers and are able to self-reproduce and evolve on the basis of template synthesis of their polymer components" Arrhenius o Life is defined as a system capable of: i. Self-organization ii. Self-replication iii. Evolution through mutation iv. Metabolism v. Concentrative encapsulation Keszthelyl o "life is metabolism and proliferation" De Duve (1991) o The ability of a system to maintain itself in a state far from equilibrium, grow and multiply, with the help of a continual flux of energy and matter supplied by the environment Most proposed examples have problems, often in the form of robust counter examples e.g. o Metabolic definitions of life have difficulty excluding fire (which grows and reproduces) o Thermodynamic definitions have difficulty excluding mineral crystals (which create and sustain local order, and may also reproduce) o Living sterile organisms cannot reproduce, so they are "not capable of Darwinian evolution" - while it is intuitively clear that living mules are alive, based on a Darwinian definition, they are not. In spite of many different approaches, we are still lacking an adequate and generally accepted definition of life This difficulty in defining our object of study adds an important factor of completely and uncertainty to the discussions of its existence, and especially to the search for life in other parts of the universe. "Life as We Know It" There are currently three ways that scientists search for extraterrestrial life 1. In situ (including sample return) searches within the solar system
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2.The spectral examination of planetary (including extrasolar planetary) atmospheres for chemical evidence of life 3.Searches for the evidence of extraterrestrial technology As we lack an agreed and precise understanding of the nature of life searches for life within our solar system are searches for 'life as we know it' i.e. life based upon 1.Liquid water a. While carbon based molecules and sources of energy are relatively common in the solar system, It appeared for a long time that water was rare outside of the Earth. b.
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This note was uploaded on 10/23/2010 for the course ANAT Anat 182 taught by Professor Vali during the Winter '10 term at McGill.

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Cosmic Foundations of the Origin of Life - Cosmic...

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