This preview shows pages 1–2. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.View Full Document
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....
View Full Document
This note was uploaded on 08/31/2009 for the course GEOL 3300 taught by Professor Staff during the Spring '08 term at Colorado.
- Spring '08