What does catastrophic climate change look like? Mars can help answer that question. The Red Planet today is a desert world, cold and dry. Billions of years ago, however, Mars probably had a thick atmosphere that kept the planet warm enough to have water flowing on the surface. To investigate how Mars lost that abundant atmosphere, NASA launched the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft on November 18, 2013. The spacecraft will orbit Mars and examine the processes that are stripping away what remains of the planet’s fragile upper atmosphere. Understanding what happened on Mars will give us new insight into the habitability of planets and global climate change. Watch the video to see what Mars's radical transformation might have looked like.