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

Have you ever found that to describe something you had to go to the dictionary and search for just the right word?

The south polar terrain is so full of unearthly features that we had to visit Mr. Webster to find a suitable term. "Araneiform" means "spider-like". These are channels that are carved in the surface by carbon dioxide gas. We do not have this process on Earth.

The channels are somewhat radially organized and widen and deepen as they converge. In the past we've just refered to them as "spiders." "Isolated araneiform topography" means that our features look like spiders that are not in contact with each other.

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.