NASA on Thursday shared an image showing many-legged shapes covering Mars’ South Pole — but the “spiders” are less scary (and less musically inclined) than you might think.
The image actually shows radiating mounds that, according to NASA, form each Martian spring when the sun begins to warm the frozen carbon dioxide (known on Earth as dry ice) that forms the planet’s southern ice cap. When the carbon dioxide warms, it transitions from its solid state into a gas — but it appears to “melt” from the bottom up, so that gas remains trapped beneath the surface.
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As the carbon dioxide gas expands, the mounting pressure eventually cracks through the surface, creating the veiny “spider” formations on Mars, which are formally known as “araneiform topography.” That’s a fancy way of saying “spider-like,” since “aranei” is Latin for “spider.” The dark spots in the image, meanwhile, are formed by dust deposited around vents where the CO2 erupts.
The image was captured by NASA’s Mars Reconnaissance Orbiter on May 13 of this year using the High Resolution Imaging Science Experiment telescopic camera, or HiRISE. HiRise was built by Ball Aerospace, and has a resolution making objects as small as 3 feet in size recognizable. It was launched in 2005.
The fact that so much ice on Mars is formed from carbon dioxide, rather than water, is just one of the challenges facing plans to colonize the Red Planet. The Mars Reconnaissance Orbiter, though, has previously discovered evidence of thin layers of water ice that exist beneath the surface of roughly one-third of the planet, and could be easily accessed by astronauts at certain locations.