According to scientists at Oxford University, Mars' atmosphere likely once had more oxygen than Earth's. They came to this conclusion when comparing rocks found by NASA's Spirit rover with Martian meteorites that have landed on Earth. Bernard Wood and his team inferred that the Red Planet once had "a significant amount of oxygen." Continue reading for a video and more information.
Here's what Bernard Wood adds: "It appears that the 4 billion year old rocks come from a more oxidized environment than the younger meteorites. Our conclusion is the source of that oxygen most likely has to do with the atmosphere. One model for Mars is that early in its history, about 4 billion years ago, it was wet and warm. It sounds a bit like Florida is today."