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This interactive is used in Chapter 7. This Interactive helps explain why Earth can retain a life-sustaining atmosphere with oxygen, but Mars cannot. Some of the same principles that apply to the Escape Velocity Interactive also apply here, like the impact of the planet’s mass. But there’s more to it with atmospheres, as surface temperature and the heaviness of the molecules also come into play. Try out some combinations of the key variables, and watch as the atmospheres evolve. You can plot multiple trials on the graph to understand what’s happening.