The spiral shape of Mars' polar caps has long intrigued us. But a new study reveals that it could help us better reconstruct the evolution of the Martian climate over the last few million years.
in summary
In this red landscape, a little touch of white. polar ice capspolar ice caps of Mars do not go unnoticed. Although the planet is arid, the polar regions have managed to preserve over time a small crustcrust ice. From 400 to 1,000 meters thick, these caps are composed of a stack of levels of water ice and dust. They also have an astonishing spiral shape.
But why this morphologymorphology ? And how can it be useful to us in understanding the history of Mars and in particular its climateclimate ?
In this photograph acquired on April 17, 2000 by the Mars Orbiter Camera (MOC) of Mars Global Surveyor (MGS), we see the southern polar cap of Mars and its astonishing morphology. © Nasa
Winds erode Mars' polar caps
Researchers at Dartmouth College have been looking into these questions, building on a hypothesis put forward in a previous study. This study proposes that the spiral shape, which is linked to the presence of high relief and in particular escarpments within the ice sheet, is caused by katabatic winds.
Example of the katabatic wind phenomenon on Earth. © ZeevStein, Wikimedia CommonsCC by-sa 4.0
These windswinds are produced by the imbalance of a air massair mass cold which, being denser, will flow along a slope. This phenomenon can produce very high wind speeds, which will erode the relief. The sedimentary particles transported will then be deposited further away, leading to the formation of ” wallswalls ” instead asymmetricalasymmetricalin constant migration. The analysis of numerous images of the polar caps of Mars shows that the “spiral” effect could well be linked to this process. But not only. The morphology of the escarpments indeed shows certain variations which suggest that the katabatic wind regime has undergone changes over time. A valuable clue for reconstructing the paleoclimate of Mars.
The data, published in the journal Journal of Geophysical Research: Planetsthus suggest that the Martian climate underwent a change 4 to 5 million years ago, leading to a modification of the wind regime in the polar region.
