Where Did Mars' Atmosphere Go?

More and more evidence suggests that billions of years ago, liquid water may have flowed on the surface of Mars. If water was present, there must have been a thick atmosphere to prevent it from freezing. However, around 3.5 billion years ago, water dried up on Mars, and the atmosphere rich in carbon dioxide rapidly thinned, leaving behind the thin Martian atmosphere we see today.

Where did Mars' atmosphere go? This question has been one of the core mysteries in Mars' 4.6 billion-year history.

Two geologists from MIT propose that the answer might lie within the clays of Mars. In a paper published in Science Advances, they speculate that much of Mars' lost atmosphere might be locked in the clay covering the Martian crust.

The research team suggests that when water was present on Mars, liquid water could have passed through certain types of rocks, triggering a series of slow chemical reactions that gradually pulled carbon dioxide out of the atmosphere and converted it into a form of carbon that could be stored in Martian clays for billions of years.

The researchers also propose that this sequestered carbon dioxide on Mars could potentially be extracted in the future and converted into propellant, providing fuel for future missions between Mars and Earth.