Lecture12 - 1 Extraterrestrial Life Spring 2008 Origin of life on Earth Two approaches • bottom-up which of the chemical structural parts of

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Unformatted text preview: 1 Extraterrestrial Life: Spring 2008 Origin of life on Earth Two approaches: • bottom-up - which of the chemical / structural parts of modern life could have formed from abiotic processes on the early Earth? • top-down - which of the constituents of current cells could have been part of earlier, simpler life forms? Basic requirements: • genetic information (DNA) • catalytic molecules (proteins) • cell membranes (lipids) Extraterrestrial Life: Spring 2008 Miller-Urey experiment 1953 experiment: mixture of several simple gases (water, hydrogen, methane and ammonia) was exposed to sparks (“lightning”) and cycled through a model of the ocean / atmosphere Extraterrestrial Life: Spring 2008 Result: large number of complex organic molecules formed in the experiment, including a number of amino acids …within weeks of the discovery of the structure of DNA… Extraterrestrial Life: Spring 2008 Experiment has been repeated many times: results stand, under these conditions amino acids are synthesized easily Are the conditions a realistic depiction of the early Earth? H 2 O, H 2 , CH 4 and NH 3 are major constituents of the atmosphere of the giant planets . Chemically, this is a reducing atmosphere, very different from the oxidizing conditions on the Earth today. Early Earth was likely devoid of oxygen, atmospheric composition would have been controlled by volcanic outgassing....
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This note was uploaded on 08/31/2009 for the course GEOL 3300 taught by Professor Staff during the Spring '08 term at Colorado.

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Lecture12 - 1 Extraterrestrial Life Spring 2008 Origin of life on Earth Two approaches • bottom-up which of the chemical structural parts of

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