The European Space Agency's (ESA) Mars Express probe recently captured stunning images of the Red Planet's south pole. It thus reveals an impressive winter landscape. Contrary to what one might imagine, however, it is not traditional snow, but layers of dry ice and dust which cover the Martian surface.
A frozen landscape, but not like on Earth
In winter, the south pole of Mars offers an impressive visual spectacle, far from what one might imagine. When Martian winter hits this region, temperatures plunge up to -123°C and cover the surface of the planet with a thick layer of ice. However, unlike the snow we know on Earth, there is nothing traditional about this Martian ice. Unlike terrestrial flakes made from melted water, those on Mars are in fact composed of two elements: water ice and carbon dioxidealso called dry ice.
The main difference is in the behavior of these elements. While on Earth water snow falls in the form of solid crystals, water ice on Mars undergoes an astonishing phenomenon. Due to the planet's extremely thin atmosphere, Martian water ice sublimes directly into gaswithout going through the liquid stage. This phenomenon occurs before the ice even hits the ground, making it invisible to the naked eye. On the other hand, dry ice reaches the surface and then forms thick layers on the Martian soil.
This particularity gives rise to fascinating and atypical landscapes. Images captured by the Mars Express probe in the Australe Scopuli region at the south pole show formations that extend over vast areas. This landscape resembles a magical winter, but it is far removed from the snowy scenes we imagine on Earth. It is an extremely cold and strange environment where dry ice and carbon dioxide dust create an unexpected and unique spectacle.
The Sun and the strange dance of layers of ice
Although conditions on Mars are frigid, the Sun plays a critical role in how these ice layers behave. The images here were captured in June, which corresponds to Martian summer in the southern hemisphere. During this period, the Sun's rays begin to heat the Martian surface, but this phenomenon is not without consequences. Indeed, the heat of the Sun causes a phenomenon called sublimation during which dry ice transforms directly from the solid state to the gaseous state without passing through the liquid phase.
This process causes pressure to build up beneath the ice layers, creating cracks on the surface. These cracks then release jets of gas that spray black dust onto the Martian surface, forming distinctive fan-shaped patterns. This phenomenon is all the more interesting because the sublimation of dry ice causes a sort of miniature explosion at each crack, ejecting Martian dust particles into the air, which are then redeposited on the ground. in circular or fan patterns. These patterns are visible in images captured by the Mars Express probe, providing a unique insight into the dynamics of the planet's south pole.
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