Volunteers find ’spiders’ on Mars - but not where they expected

A high resolution image from the HiRISE camera onboard NASA's Mars Reconnaissance Orbiter of one of the new Martian araneiform (or "spider") locales outside of the South Polar Layered Deposits discovered by the Planet Four: Terrains volunteers. Image credit:  NASA/JPL/University of Arizona Armchair astronomers have helped Oxford University scientists discover landforms known as 'spiders' on parts of Mars where they were previously thought not to exist. The 'spiders' are named for their arachnid-like appearance and are a type of land erosion where networks of cracks form on Martian soil, completely different to anything on Earth. The discovery was made by volunteers working on behalf of Planet Four: Terrains , an online project hosted by Zooniverse, the world's largest and most popular people-powered research platform. Araneiforms - the scientific name for these features - occur at the planet's South Pole and form when carbon dioxide turns to ice during the Martian winter. As the seasons change, direct sunlight penetrates the translucent ice, warming the land beneath. The land surface then gets eroded as the gas races out and rips off little bits of dirt, forming spindly branches which resemble spider legs.