Wishing for a snowy Christmas this year? Well, even if there isn’t any snow in your area, you can still appreciate these pictures of a “winter” wonderland on Mars.
Captured by the German-made High Resolution Stereo Camera (HRSC) aboard the European Space Agency’s (ESA) Mars Express orbiter in June 2022, along with images taken by NASA’s Mars Reconnaissance Orbiter utilizing its High-Resolution Imaging Science Experiment (HiRISE) camera in September 2022, these visuals highlight what seems to be a snowy scene in the Australe Scopuli region of Mars, close to the planet’s southern polar region.
However, the “snow” observed here significantly differs from what we experience on Earth.
In reality, it consists of carbon dioxide ice, and at Mars’ south pole, there exists a 26-foot-thick (8-meter-thick) layer of it throughout the year. (These images were actually captured around the summer solstice, rather than during winter — it’s quite cold in this region all year round.)
So, why does it appear as though there’s merely a dusting of “snow” in these images? The darker regions are layers of dust that have settled atop the ice. The dust is usually located deep beneath the ice, but a seasonal phenomenon pushes some of it to the surface.
NASA’s Mars Reconnaissance Orbiter also detected winter frost adorning the sides of dunes on Mars. This frost helps prevent erosion, NASA states, keeping the dust that forms the dunes in position until the thawing season in spring arrives.
As sunlight warms the carbon dioxide ice at the south pole of Mars during the summer, the ice begins to sublimate, transitioning directly from a solid to vapor. As this occurs, bubbles of trapped gas develop within the ice.
Eventually, pressure builds sufficiently to create a small gas eruption, strong enough to propel the dark dust located beneath the ice into the atmosphere. As the dust descends back to the ground, the wind transports it into these swirling formations. (Interestingly, a similar process results in the spider-like features observed on the Martian terrain.)
Therefore, what may seem like a picturesque winter tableau in these Mars Express images is, in fact, a dynamic summer environment, where gas jets disperse dust across the landscape. Well, at least it’s still frigid outside — just a casual -193°F (-125°C).