This program, developed at the Denver Museum of Nature and Science, and supported by a grant from NASA, is about the climates of Earth, Venus, and Mars. Four Billion years ago, the climates on these three planets were very similar, but today they are very different. What happened? Understanding and comparing these planets gives us insights into the forces which determine the climate on Earth. This program is available in forms for either a live presentation or an autorun show. There are PowerPoint slides that can be used on an additional screen for the live presentation.