I call the surface of the following picture sponge terrain because is full of holes.  Walking across this area has got to be a workout.  Most of the holes are about the size of a small city lot for a house.  This terrain covers nearly all of the floor of a large crater.

Selected References

Arfstrom, J and W Hartmann. 2005.  "Martian flow features, moraine-like ridges, and gullies:                           Terrestrial analogs and interrelationships."  Icarus. 174: 321-335.
Authors use many pictures to describe features that resemble ones made by glaciers on Earth.  Icarus often publishes good articles about Mars.

Christensen, Philip.  2005.  "The many Faces of Mars.  Scientific  American. July: 32-39.  This excellent easy-to-read article covers the chemistry of the Martian rocks as well as the basic geology of various landscapes.  The author brings many current ideas and observations together.  Scientific American is found in many public libraries.

Christensen, Philip.  2003.  "Formation of recent Martian gullies through melting of extensive water-rich snow deposits."  Nature.  422:  45-48.  Article explains the formation of gullies by the melting of snowpacks.  Nature can be found in most community college libraries.

Milliken, R, J. Mustard, and D. Goldsby.  2003.  "Viscous flow features on the surface of Mars:  Observations from high-resolution Mars Orbiter Camera (MOC) images."  Journal of Geophysical Research 108:  5057.

Murray, J. et.al.  2005.  "Evidence from the Mars Express High Resolution Stero Camera for a frozen sea close to Mars' equator."  Nature.  434:  352-356.  Article includes pictures of a possible frozen Martian sea.  Nature can be found in most community college libraries.

Schorghofer, N., O Aharonson, S. Khatiwala.  2002.  "Slope streaks on Mars:  Correlations with surface properties and the potential role of water."  Geophysical Research Letter. 29: 41

Revised March 2006