|The ice evolution on Mars over a characteristic obliquity cycle. The angle between the white arrows and the dotted line denotes the Martian obliquity. At high obliquity, the northern cap becomes unstable and looses a few centimeters of ice each year. This ice is then deposited in equatorial zones. When the obliquity decreases, ice comes back at high latitudes. When the equatorial reservoir disappears, high-latitude ice deposits become unstable too. A fraction sublimates and lays out again towards the poles which contributes to the creation of Martian polar caps, while an other fraction is buried under a protecting dust lag. Image credit: ASD/IMCCE-CNRS, adapted from Jim Head/Brown University and NASA/JPL.