Peculiar spots, fan-like markings, and spider-shaped features on Mars’ southern ice cap are seasonal formations, researchers announced today. The shapes are formed by thin layers of dark dusty material that are sprayed by roaring jets of carbon dioxide that erupt through the ice cap. This dusty material may also be the reason that the southern ice cap doesn’t reflect much light. The mystery markings, generally 50 to 150 feet wide, appear every southern spring as the Sun rises over the red planet’s ice cap. They last about three to four months.