Obliquity-oblateness feedback on Mars

A simple model is presented for the coupled dynamics of the orbit-rotation- climate system of Mars. Changes in the orientation of the spin pole, relati ve to the orbit pole, influence the spatiotemporal pattern of incident radi ation and thus drive climatic mass transport into and out of the polar regi ons on a variety of timescales. Changes in the mass distribution occur from direct climatic forcing and compensating viscous flow in the interior. The net change in mass distribution influences the rate of spin axis precessio n and thereby influences obliquity. The rate of secular obliquity drift dep ends on several poorly known parameters, including the magnitudes and respo nse times of volatile inventories and viscosity structure within Mars. Even relatively modest secular obliquity drift can lead to trapping in nearby r esonances. The dissipative nature of the coupled dynamical system makes rec onstruction of past evolution much more difficult than for a purely inertia l system. The long-term obliquity history of Mars is dominated by climate.