ESA has published reprocessed images of the Australe Scopuli region of Mars captured by its Mars Express space probe’s High Resolution Stereo Camera (HRSC). The area is covered in what appears to be snow but is actually carbon dioxide ice and dust. Despite the differences, the view is reminiscent of a Christmas landscape, especially the kind common at altitudes where it normally snows on Earth. It’s still a significant day because, on December 25, 2003, Mars Express entered Mars’ orbit.
The solstice on Mars doesn’t occur on the same day as on Earth unless there’s a coincidence. However, seasons do exist on the red planet, which becomes white in some areas as carbon dioxide is deposited in a cycle that, despite appearances, is different from that of the water that generates snow on Earth.
Conditions on the red planet lead to areas like Australe Scopuli where carbon dioxide on the surface freezes and forms an icy layer that traps the gases beneath it. When the Sun heats the ice outer layer, the temperature rises enough to increase the pressure of the gases until they escape in the form of small geysers. On the outside, the carbon dioxide gas freezes and settles on the ground. In this process, the carbon dioxide is mixed with impurities such as sand and dust, making the ground look dirty.
The original images were captured by the Mars Express space probe’s HRSC camera on June 16, 2022, as winter was ending in Mars’ southern hemisphere. Temperatures on the surface of Australe Scopuli were around -125° Celsius, still very cold but already enough for the ice to sublimate in some areas, which are recognizable because they appear darker in the image.
Studying an area like Australe Scopuli allows to learn a lot about the carbon dioxide cycle and the winds, as the ice deposits are aligned with the prevailing wind direction. The contrast of white and dark layers between the hills and valleys creates a landscape that is alien and familiar at the same time.
The Mars Express space probe has been sending images and data for 21 Earth years now. Over the years, other space probes from various agencies have reached Mars and are adding their support to the study of the red planet, but ESA continues to extend the mission of Mars Express for the scientific value of the contributions it continues to offer.
