Once a wet and warm world, Mars is a cold desert with thin air. Scientists have long wondered what happened to the planet’s thick, carbon dioxide-rich atmosphere that disappeared 3.5 billion years ago. A new study by MIT geologists suggests that most of the lost gas may have been trapped in the crust of Mars. Researchers say that when water flowed to Mars billions of years ago, it started to react chemically with some rocks, especially igneous rocks rich in olivine.
These reactions draw carbon dioxide out of the atmosphere and turn it into methane, which is trapped in Earth’s sediments, especially smectite. On Earth, similar processes occur, with smectite clay holding carbon well. The MIT team extended this work to Mars, and found that if the planet were covered by a layer of smectite 1,100 meters long, it could contain up to 80 percent of the early Martian carbon dioxide, 1.7 times of pressure.
This process may play a major role in climate change on Mars, reducing carbon dioxide and thinning the atmosphere, leaving the cold, dry planet we see today. These findings suggest that this stored methane could one day be used as an energy source for future missions to Mars.