A 510,000‐Year Record of Mars' Climate

Abstract

Characterizing the history of processes controlling Mars' recent climate under different orbital configurations is a major Mars science goal (Banfield et al., 2020). Mars' polar deposits contain a record of H 2 O transport between north and south polar, mid-latitude, and equatorial reservoirs in response to Mars' orbital element oscillations (Becerra et al., 2021;Smith et al., 2020). 4-5 Myr ago, a 10(+)-Myr duration high obliquity state favoring tropical H 2 O glaciation (Head et al., 2003) transitioned to a low obliquity state (Laskar et al., 2004). Within <∼1 Myr, tropical H 2 O ice migrated to the midlatitudes and poles (Montmessin et al., 2004), followed by gradual transport of midlatitude H 2 O ice to the poles (Levrard et al., 2007;Mellon & Jakosky, 1995).Mars' recent (<∼3.5 Myr) H 2 O cycle is probably driven by 10 5 -yr obliquity and 10 4 -yr longitude of perihelion cycles. Midlatitude-to-pole H 2 O transport is likely obliquity mediated, but quantitative present-day and historical transport rates are highly uncertain (Montmessin et al., 2017). Interhemispheric polar H 2 O ice transport is likely mediated by longitude of perihelion precession; Mars' present configuration favors north-to-south polar H 2 O ice transport, reversing at opposite perihelion configuration (Montmessin et al., 2007). However, the CO 2 south polar residual cap (SPRC) is a perennial cold-trap sink of H 2 O (Richardson & Wilson, 2002). Presently, ∼3 × 10 12 kg of H 2 O ice participates in an equilibrated seasonal sublimation-deposition cycle. Approximately one-third exchanges between hemispheres and ∼two-thirds recycles within the northern hemisphere (Montmessin et al., 2017).Previous studies of H 2 O ice and dust layers in the North and South Polar Layered Deposits (NPLD, SPLD) and near-polar ice deposits extracted ∼0.1-0.5 mm yr −1 deposition rates averaged over a few Myr using wavelet analysis (Becerra et al., 2017(Becerra et al., , 2019Sori et al., 2022) and simplified stratigraphic development modeling (Hvidberg et al., 2012). However, these averaging timescales are much longer than orbital element periodicities, the deposits have loose temporal constraints (Tanaka et al., 2008), and no model has yet produced a one-to-one correlation between modeled and observed layers in these deposits (Hvidberg et al., 2012;Levrard et al., 2007). Thus, quantitative transport rates as a function of Mars' orbital configuration along any leg of Mars' global H 2 O cycle have remained elusive.