The European Space Agency's "Mars Express" spacecraft captured clear signs of "spiders" scattered across the southern polar region of Mars. Members of the Mars Express mission team stated, "Instead of being real spiders, the Martian spiders form when spring sunlight hits layers of carbon dioxide accumulated during the dark winter months. The sunlight causes the carbon dioxide ice at the bottom of the layer to turn into gas, which then accumulates and breaks through the overlying ice sheets. The gas bursts forth in the spring on Mars, pulling dark material to the surface as it moves, and shattering ice layers that can be up to one meter thick."
The team further explained, "The resulting gas, laden with dark dust, erupts through cracks in the ice like long fountains or hot springs, before retreating and settling on the surface." This process creates dark spots that range in width from 45 meters to 1 kilometer (148-3280 feet). It creates distinctive "spider" patterns etched beneath the ice, thus these dark spots are a clear sign that spiders may be lurking below.
The team clarified, "The dark spots can be seen throughout the Mars Express image. However, most are visible as small spots in the dark region to the left, which lies on the outskirts of an area of Mars known as Inca City. The reason for this name is not obscure, as the network of quasi-geometric linear hills reminds us of Inca ruins."
The Martian "Inca City," officially known as Angustus Labyrinth, was discovered in 1972 by NASA's Mariner 9 probe. Scientists stated they are still uncertain exactly how "Inca City" formed, suggesting that sand dunes may have turned to stone over time. They added, "Materials such as magma or sand may have seeped through the fractured plates of Martian rock. Alternatively, the hills could be meandering structures associated with glaciers. The 'walls' of Inca City appear to outline part of a large circle with a diameter of 86 kilometers (53.5 miles)."
Scientists suspect that "Inca City" lies within a large crater formed when a space rock impacted the planet's surface. The team noted, "It is likely that this impact caused fractures to spread across the surrounding plain, which then filled with rising volcanic lava, later eroding over time."
