This caption is part of a December 2007 AGU presentation "Spring at the South Pole of Mars."

The south polar terrain on Mars contains landforms unlike any that we see on Earth, so much that a new vocabulary is required to describe them. The word "araneiform" means "spider-like." There are radially organized channels on Mars that look spider-like, but we don't want to confuse anyone by talking about "spiders" when we really mean "channels," not "bugs."

The first subimage shows an example of "connected araneiform topography," terrain that is filled with spider-like channels whose arms branch and connect to each other. Gas flows through these channels until it encounters a vent, where it escapes out to the atmosphere, carrying dust along with it. The dark dust is blown around by the prevailing wind.

The second subimage shows a different region of the same image where the channels are not radially organized. In this region they form a dense tangled network of tortuous strands. We refer to this as "lace."

For information about NASA and agency programs on the Web, visit: http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.