Dynamic and Isotopic Evolution of Ice Reservoirs on Mars

TL;DR

This study models the exchange of water and isotopes among Mars's ice reservoirs, linking climate variations to stratigraphy and isotopic composition, and suggests isotopic sampling can reveal climate cycles not visible in layer thicknesses.

Contribution

It introduces a dynamic model connecting Mars's climate variations with ice stratigraphy and isotopic composition, highlighting the role of precession and obliquity in ice evolution.

Findings

Isotopic changes are driven by interactions among ice reservoirs.

Layer thicknesses mainly controlled by obliquity variations.

Isotopic sampling can reveal climate oscillations not seen in layer thicknesses.

Abstract

The layered polar caps of Mars have long been thought to be related to variations in orbit and axial tilt. We dynamically link Mars's past climate variations with the stratigraphy and isotopic composition of its ice by modeling the exchange of H2O and HDO among three reservoirs. The model shows that the interplay among equatorial, mid-latitude, and north-polar layered deposits (NPLD) induces significant isotopic changes in the cap. The diffusive properties of the sublimation lags and dust content in our model result in a cap size consistent with current Mars. The layer thicknesses are mostly controlled by obliquity variations, but the precession period of 50 kyr dominates the variations in the isotopic composition during epochs of relatively low and nearly constant obliquity such as at present. Isotopic sampling of the top 100 meters may reveal climate oscillations unseen in the layer thicknesses and would thus probe recent precession-driven climate cycles.