When scientists first examined the layered structure of Mars’ northern ice cap, somewhat crudely detected by the Mariner 9 orbiter in the early 1970s, they speculated the bands were composed of alternating tiers of ice and dust accumulated over years. Researchers have now used more recent data collected by the Mars Global Surveyor to make measurements of the layers down to fractions of inches using the high resolution Mars Orbiter Camera aboard the Mars Global Surveyor. What they’re learning about the layers of Martian history may tell them something about what controls the climate of the Red Planet.