A 510,000-Year Record of Mars' Climate

Mars' polar layered deposits record its climate history. However, no deposit yet analyzed provides a global water cycle record that can be tied to a specific orbital history. Here, I fill this gap by analyzing H2O ice layer formation in Mars' south polar Massive CO2 Ice Deposit (MCID), a 510,000-year climate record. Statistical analyses of similar to 10(9) formation model runs compared to observed stratigraphy indicate a variable H2O deposition rate of similar to 1, 0.1, and 0.01 mm yr(-1) at 20, 24, and 28 degrees obliquity, respectively-likely recording the obliquity-dependent midlatitude-to-pole H2O transport rate. The MCID record allows unprecedented obliquity-driven H2O ice deposition rate derivation because of its well-defined age relative to other deposits and its CO2 cold-trapping effect, which simplifies local seasonal and long-term H2O flux. The recovery of an orbit-resolved H2O transport rate is an essential step in elucidating Mars' global, orbit-driven water cycle.