Mars is a host to all kinds of mysteries. Many scientists believe Mars had a much thicker CO2 atmosphere. But, if it did, the question remains: Where did it go? Some think the lack of a magnetic field led to solar winds carrying the atmosphere mostly off into space. With the atmosphere it does have, much of it is made of methane, but scientists don’t know where the methane comes from. There’s also the question of water and life on Mars. Mysteries scientists are actively trying to get to the bottom of.