Thanks to data from ESA's Mars Express mission, combined with models of the Martian climate, scientists can now suggest how the orbit of Mars around the Sun affects the deposition of water ice at the Martian South Pole.
Early during the mission, the OMEGA instrument (Visible and Infrared Mineralogical Mapping Spectrometer) on board Mars Express had already found previously undetected perennial deposits of water-ice. They are sitting on top of million-year old layered terrains and provide strong evidence for a recent glacial activity.
However, only now a realistic explanation for the age of the deposits and the mechanism of their formation could finally be suggested. This was achieved thanks to the OMEGA mapping and characterisation of these ice deposits, combined with the computer-generated Martian Global Climate Models (GCMs).
The mapping and spectral analysis by OMEGA has shown that the perennial deposits on the Martian South Pole are of essentially three types: water-ice mixed with carbon dioxide (CO2) ice, tens-of-kilometres-wide patches of water-ice, and deposits covered by a thin layer of CO2 ice.
The discovery of the ice deposits of the first type confirms the long-standing hypothesis that CO2 acts as a cold-trap for water-ice. But how were the other two types of deposits, not trapped by CO2, accumulated and preserved over time"
Franck Montmessin, from the Service d'Aronomie du CNRS/IPSL (France) and lead author of the findings, explains how the deposits of water ice at the Martian's poles 'behave'. "We believe that the deposits of water-ice are juggled between Mars North and South Poles over a cycle that spans 51 000 years, corresponding to the time span in which the planet's precession is inverted." Precession is the phenomenon by which the rotation axis of a planet wobbles.
Montmessin and colleagues came to the conclusion by turning back time in their Mars climate computer model. This was done
Contact: Agustin Chicarro
European Space Agency