On the origin of perennial water ice at the south pole of Mars: A precession-controlled mechanism?

• Published in: Journal of Geophysical Research: Planets
• Main Authors: Montmessin, Franck, M. Haberle, R., Forget, François, Langevin, Yves, T. Clancy, R., Bibring, Jean-Pierre
• Other Authors: Service d'aéronomie (SA), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Space Science and Astrobiology Division at Ames, NASA Ames Research Center (ARC), Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École des Ponts ParisTech (ENPC)-École polytechnique (X)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Space Science Institute Boulder (SSI)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2007
• Subjects: [SDU]Sciences of the Universe [physics]; North Pole; South Pole; Ice cap; South pole
• Online Access: https://hal.archives-ouvertes.fr/hal-00181320; https://hal.archives-ouvertes.fr/hal-00181320/document; https://hal.archives-ouvertes.fr/hal-00181320/file/Montmessin_et_al-2007-Journal_of_Geophysical_Research__Planets.pdf; https://doi.org/10.1029/2007JE002902

The poles of Mars are known to have recorded recent (<107 years) climatic changes. While the south polar region appears to have preserved its million-year-old environment from major resurfacing events, except for the small portion containing the CO2 residual cap, the discovery of residual water ice units in areas adjacent to the cap provides compelling evidence for recent glaciological activity. The mapping and characterization of these H2O-rich terrains by Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité (OMEGA) on board Mars Express, which have supplemented earlier findings by Mars Odyssey and Mars Global Surveyor, have raised a number of questions related to their origin. We propose that these water ice deposits are the relics of Mars' orbit precession cycle and that they were laid down when perihelion was synchronized with northern summer, i.e., more than 10,000 years ago. We favor precession over other possible explanations because (1) as shown by our General Circulation Model (GCM) and previous studies, current climate is not conducive to the accumulation of water at the south pole due to an unfavorable volatile transport and insolation configuration, (2) the residual CO2 ice cap, which is known to cold trap water molecules on its surface and which probably controls the current extent of the water ice units, is geologically younger, (3) our GCM shows that 21,500 years ago, when perihelion occurred during northern spring, water ice at the north pole was no longer stable and accumulated instead near the south pole with rates as high as 1 mm yr−1. This could have led to the formation of a meters-thick circumpolar water ice mantle. As perihelion slowly shifted back to the current value, southern summer insolation intensified and the water ice layer became unstable. The layer recessed poleward until the residual CO2 ice cover eventually formed on top of it and protected water ice from further sublimation. In this polar accumulation process, water ice clouds play a critical role since they ...