Two European Mars orbiters have captured intriguing images of the Australe Scopuli region, revealing a variety of unusual surface features emerging from melting ice at the Red Planet's south pole. The European Space Agency's (ESA) Mars Express mission provided these insights on April 2, 2024, coinciding with the arrival of spring in Mars' southern hemisphere.
Utilizing the High Resolution Stereo Camera (HRSC), the Mars Express images depict seasonal polar caps primarily composed of carbon dioxide ice, with some water ice present. As spring progresses, the ice undergoes sublimation, transforming directly from solid to vapor and releasing significant amounts of gas into the thin Martian atmosphere, as noted in an ESA statement on October 9.
With the onset of autumn, cooler temperatures lead to the condensation of vapor, resulting in the formation of expansive polar caps as the southern hemisphere transitions into winter. This freeze-thaw cycle gives rise to a range of distinctive surface features, some of which are notably darker than their icy surroundings, earning the designation of 'cryptic terrain.'
The imagery reveals thick layered deposits containing trapped dust on one side, contrasted by smoother layers on the other. Central to the images is the darker terrain, which, upon closer inspection, displays patterns of varying polygon shapes with icy edges, believed to be shaped by freeze-thaw cycles over extended periods, potentially spanning years or centuries.
ESA's Trace Gas Orbiter (TGO) also contributed to the observations, capturing high-resolution images of different areas in Mars' southern hemisphere, showcasing frost-fringed polygons.
Additionally, the released images highlight fan-shaped deposits ranging from tens to hundreds of meters in size, alongside jets formed by vapor escaping through the melting ice layer, transporting dark dust from beneath. This darker material, upon settling on the surface, absorbs more sunlight, accelerating the melting of Martian ice and causing the dark material to sink.
Researchers emphasize that studying these diverse icy features is crucial for understanding Mars' climate history, providing insights into the planet's past environmental conditions.