Pseudocraters on Mars

In the Cydonia region of southern Acidalium Planitia are small, low‐relief, apparently volcanic domelike structures, whose size, morphology, and general occurrence suggest they are martian analogs of terrestrial pseudocraters, a type of phreatic eruption. Average base diameters are about 800 m, which is somewhat larger than typical Icelandic examples. All the domes have summit pits; elongate domes generally have elongate summit pits or, in extreme cases, double pits. The greatest concentration of these domes is in a region of subdued fractured plains which may be old volcanic flows. Pseudocraters on the earth are produced when lava flows over water‐logged ground. On Mars surface or subsurface ice was the likely medium that produced the steam eruptions resulting in cratered domelike structures on the lava surfaces.