Arachnophobes need not fear: a new image of Martian “spiders” from the European Space Agency (ESA) actually shows seasonal eruptions of carbon dioxide on the red planet.
The dark, spindly formations were spotted in a formation known as the Inca City in March‘southern polar region. Images taken by ESA’s Mars Express orbiter and the ExoMars Trace Gas orbiter show dark clusters of dots that appear to have tiny legs, much like baby spiders huddled together.
The formations are actually gas channels measuring between 45 meters and 1 kilometer in diameter. They occur when the weather begins to warm in the Southern Hemisphere during the Martian spring, melting layers of carbon dioxide ice. The heat causes the lowest layers of ice to turn into gas or sublimate.
As the gas expands and rises, it explodes out of the overlying layers of ice, carrying the dark dust from the solid surface with it. This dust shoots up from the ice before pouring onto the top layer, creating the spider-like cracked pattern seen here. In some places, geysers erupt through ice up to 1 m thick, depending on ESA.
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The Inca city is also known as Angustus Labyrinthus. It gets its name from its linear ruin-like ridgelines, once thought to be petrified sand dunes or perhaps remnants of ancient Martian glaciers, which may have left behind high walls of sediment when removing them.
However, in 2002, the Mars Orbiter revealed that the Inca city is part of a circular feature approximately 86 km wide. This feature could be an ancient impact crater, suggesting that the geometric ridges could be intrusions of magma that broke through Mars’ cracked, heated crust after it was struck by a rogue space rock. The crater would then have filled with sediments, which would have since eroded, partly revealing magmatic formations reminiscent of ancient ruins.
