Thermokarst landscape on Mars, satellite image. This landscape includes features thought to have formed due to the influences of liquid water and ice. Examples are polygonal patterns of troughs and large scallop-shaped depressions. Fractures appear when ice-rich soil contracts each winter. Collectively, such landforms are referred to as 'thermokarst'. These observations were made by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter (MRO) spacecraft. Image published in 2013.