A 510,000‐Year Record of Mars' Climate

Abstract

AbstractMars' 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 ∼109 formation model runs compared to observed stratigraphy indicate a variable H2O deposition rate of ∼1, 0.1, and 0.01 mm yr−1 at 20, 24, and 28 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.