Fractures and pits in Northern Plains (Utopia Plains: 44.9 N, 274.7 W). Photo: NASA/JPL/Malin Space Science Systems

Although northern plains are often called "flat" or "featureless" by people who study altimetry data, clearly this isn't true. This area has an indurated (strong or cemented) crust that has been subjected to directional stress (that's why the beaded-pitted fractures are almost all aligned the same direction) and that has been undermined (hence the pitting at both the small scale -- the beaded fractures, and the large scale -- the large irregular depressions.

Dunes in Herschel Crater (Herschel Crater: 15.7 S, 228.8 W). Photo: NASA/JPL/Malin Space Science Systems

This Mars Global Surveyor image shows erosional streaks on dunes in Herschel Crater, which means that the dunes are indurated (cemented).

Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.