The Spiders from Mars might have been David Bowie's backing band here on Earth, but that term has a different meaning when we're talking about the actual Red Planet. The "spiders" make their appearance as the season turns to spring, dotting the terrain. The scenic look at the planet's South Pole comes from the space agency's Mars Reconnaissance Orbiter (MRO) and it shows "spiders" emerging from the ground. The spiders are not actually eight-legged arachnids, though.
NASA said that the active seasonal process involved does not occur on Earth, but like dry ice on our planet, the carbon dioxide ice on Mars sublimates when it warms, causing it to change from solid to gas and become trapped below the surface. The mounds form when carbon dioxide ice beneath the surface heats up and is released. As pressure builds, the gas eventually bursts through the surface to release dust that either gathers around the vent or is blown away by the wind. The dark spots in the image, meanwhile, are formed by dust deposited around vents where the Carbon dioxide erupts.
"The loss of the sublimated carbon dioxide leaves behind these spider-like features etched into the surface", NASA explained on its website. It was launched in 2005.
"In flight operations, our emphasis is on minimising risk to the spacecraft while carrying out an ambitious scientific and programmatic plan".
The MRO photographs are taken by the HiRISE imager which is operated by the University of Arizona.