Mars wasn’t always the Red Planet. Eons ago, it is possible that Mars was as lush as Earth is today. So, what happened? NASA is on the case with this enlightening video of how Mars may have lost its atmosphere. The idea behind the atmospheric “sputtering” Mars may have experienced is fairly simple to understand. But, of course, NASA is not sure this is what happened, which is why this educational video doubles as an announcement of the space agency’s newest mission: the Mars Atmosphere And Volatile EvolutioN (MAVEN) mission, which will launch sometime around December 2013.