October 20, 2009
The Thermal Emission Spectrometer on NASA's Mars Global Surveyor discovered that jets of dusty gas produce dark markings on the south polar cap. During southern winter, carbon dioxide gas condenses onto the polar cap as a thin slab of transparent ice. When the Sun rises in spring, the ice sublimates from the bottom of the layer, while the growing gas pressure lifts the slab off the ground. Gas then breaks through the slab in places, erupting in jets that carry dust scavenged from under the slab. This image is an artist's concept illustrating the jets shooting into the sky at the Martian south polar icecap as southern spring begins.