'Spiders' on Mars as seen by ESA's ExoMars Trace Gas Orbiter

This image shows features known as ‘spiders’ near Mars’s south pole, as seen by the CaSSIS (Colour and Stereo Surface Imaging System) instrument aboard ESA’s ExoMars Trace Gas Orbiter.

These features form when spring sunshine falls on layers of carbon dioxide deposited over the dark winter months. The sunlight causes carbon dioxide ice at the bottom of the layer to warm up and turn to gas, which then builds up and breaks through slabs of overlying ice. The emerging gas, laden with dark dust, shoots up through cracks in the ice in the form of tall fountains or geysers, before falling back down and settling on the surface, creating dark spots. This same process creates characteristic ‘spider-shaped’ patterns etched beneath the ice: the very same patterns shown here.

The data for this image were captured by CaSSIS on 4 October 2020. The image is centred at roughly 323°E/75°S.

This image is included in a new release from ESA’s Mars Express, which also highlighted these enigmatic features on the martian surface.

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[Image description: A slice of the martian surface is shown here. A rounded segment of an eroded crater basin is visible to the right. The key features seen across the image are dark spots with tendrils that are eerily reminiscent of spiders. These are visible in large numbers to the left, and scattered irregularly across the rest of the image.]