  Mars' polar layered deposits (PLD) are comprised of layers of varying
dust-to-water ice volume mixing ratios (VMR) that may record
astronomically-forced climatic variation over Mars' recent orbital history.
Retracing the formation of these layers by quantifying the sensitivity of
deposition rates of polar material to astronomical forcing is critical for the
interpretation of this record. Using a Mars global climate model (GCM), we
investigate the sensitivity of annual polar water ice and dust surface
deposition to various obliquities and surface water ice distributions at zero
eccentricity, providing a reasonable characterization of the evolution of the
PLD during recent low-eccentricity epochs. For obliquities between 15{\deg} -
35{\deg}, predicted net annual accumulation rates range from -1 to +14 mm/yr
for water ice and from +0.003 to +0.3 mm/yr for dust. GCM-derived rates are
ingested into an integration model that simulates polar accumulation of water
ice and dust over 5 consecutive obliquity cycles (~700 kyrs) during a low
eccentricity epoch. A subset of integration simulations predict combined
accumulation of water ice and dust in the north at time averaged rates that are
near the observationally-inferred value of 0.5 mm/yr. Three types of layers are
produced per obliquity cycle: a ~30 m-thick dust-rich (~25% dust VMR) layer
forms at high obliquity, a ~0.5 m-thick dust lag forms at low obliquity, and
two ~10 m-thick dust-poor (~3%) layers form when obliquity is
increasing/decreasing. The ~30 m-thick dust-rich layer is reminiscent of a ~30
m feature derived from visible imagery analysis the north PLD, while the ~0.5
m-thick dust lag is a factor of ~2 smaller than observed "thin layers".
Overall, this investigation provides further evidence for obliquity forcing in
the PLD climate record, and demonstrates the importance of ice-on-dust
nucleation in polar depositional processes.
