Axial Tilt of Mars

At 25.19°, Mars is tilted almost exactly like Earth (23.44°), so it runs the same seasonal machinery: solstices, equinoxes, and polar caps that grow and shrink in opposite phase. The resemblance is temporary. Without a massive moon to anchor it, Mars's spin axis responds chaotically to planetary perturbations — Jacques Laskar's integrations show the obliquity wandering between about 10° and 60° over tens of millions of years, and the current value cannot be extrapolated back beyond a few million.

The climate consequences are written in the ground. At high obliquity the poles roast in summer and ice migrates to the tropics — orbiters see the remains of glaciers on the flanks of equatorial volcanoes — while at low obliquity the atmosphere itself can collapse as carbon dioxide freezes out permanently at the poles. The layered polar deposits, kilometres of dust and ice laid down in rhythmic bands, are a tape recording of these astronomical cycles.