The dark spots in this image from ESA’s Mars Express are the telltale sign of ‘spiders’ scattered across the southern polar region of Mars. These small features form when carbon dioxide gas warms up in sunlight and breaks through slabs of overlying ice, etching branched grooves into the surface and dragging dark material up to the surface to form dark blotches.
Many such blotches can be seen within the dark region to the left of the frame, which sits at the outskirts of a part of Mars nicknamed Inca City. The reason for this name is clear, with the linear, almost geometric network of ridges being reminiscent of Inca ruins.
Credit: ESA/DLR/FU Berlin
The
This oblique perspective view looks across a part of Mars nicknamed Inca City (formally named Angustus Labyrinthus). The reason for this is no mystery, with the linear network of ridges being reminiscent of Inca ruins. Traces of features known as ‘spiders’ can be seen; these small, dark features form as carbon dioxide gas warms up in sunlight and breaks through slabs of overlying ice. Credit: ESA/DLR/FU Berlin
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. This creates dark spots of between 45 m and 1 km across. This same process creates characteristic ‘spider-shaped’ patterns etched beneath the ice – and so these dark spots are a telltale sign that spiders may be lurking below.
Another of ESA’s Mars explorers, the ExoMars Trace Gas Orbiter (TGO), has imaged the spiders’ tendril-like patterns especially clearly (see below). The spiders captured by TGO lie near, but outside, the region shown in this new Mars Express image. The Mars Express view shows the dark spots on the surface formed by escaping gas and material, while the TGO perspective also captures the spidery, web-like channels that are carved into the ice below.
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.
Credit: ESA/TGO/CaSSIS
The aforementioned dark spots can be seen all over the Mars Express image, creeping across towering hills and expansive plateaus. However, most can be seen as small spots in the dark region to the left, which sits just at the outskirts of a part of Mars nicknamed Inca City. The reason for this name is no mystery, with the linear, almost geometric network of ridges being reminiscent of Inca ruins. More formally known as Angustus Labyrinthus, Inca City was discovered in 1972 by
This oblique perspective view shows a part of Mars nicknamed Inca City. The reason for this is no mystery, with the linear, almost geometric network of ridges being reminiscent of Inca ruins. More formally known as Angustus Labyrinthus, Inca City was discovered in 1972 by NASA’s Mariner 9 probe. Credit: ESA/DLR/FU Berlin
