http://www.slate.com/blogs/bad_astronom ... ction.html http://www.slate.com/blogs/bad_astronom ... ction.html important Great Oxygenation Event Great Oxygenation Event cyanobacteria http://www.slate.com/blogs/bad_astronom ... ction.html very different atmosphere Great Oxygenation Event www.slate.com/b...extinction.html Great Oxygenation Event Poisoned Planet Poisoned Planet Great Oxygenation Event http://www.slate.com/blogs/bad_astronom ... ction.html 2.3 billion years ago Slate.com - Bad Astronomy Blog http://www.slate.com/blogs/bad_astronom ... ction.html Great Oxygenation Event important http://www.slate.com/blogs/bad_astronom ... ction.html Great Oxygenation Event Great Oxygenation Event http://www.slate.com/blogs/bad_astronom ... ction.html first-ever Great Oxygenation Event Great Oxygenation Event http://www.slate.com/blogs/bad_astronom ... ction.html http://www.slate.com/blogs/bad_astronom ... ction.html Great Oxidation Event http://www.slate.com/blogs/bad_astronom ... ction.html greatest mass extinction of them all the Great Oxidation Event Poisoned Planet | Phil Plait