Astronaut Donald Pettit champions a theory he developed while studying under Octave Levenspiel at Oregon State University. In short, it is apparent that large winged dinosaurs could not fly under today's atmospheric conditions. Pettit suggests that the solution to dino-flight is that the Earth's atmosphere was much thicker in the past, lending buoyancy to the giant animals while maintaining today's ratios of elemental composition. If this trend is extended long before the dinosaurs we end up with a hypothetical atmosphere as thick as Venus or even more. The theory then raises the question: what events caused the atmosphere to disappear?