Rupes

Rupes is a term used in planetary geology to designate a long, linear cliff or escarpment on the surface of a solid body. The word comes from Latin rupēs, meaning cliff or rock face. In the context of the International Astronomical Union (IAU) nomenclature, rupes is a standard feature type used to label scarps that cut across terrain, distinct from craters, ridges, or faults by their elongated form and abrupt topography.

Rupes can form through different processes depending on the body. They commonly result from tectonic contraction that uplifts one block against another along a thrust fault, creating a sharp topographic step. In some cases, cooling and contraction of volcanic plains can also produce scarp-like features. The orientation and length of rupes reflect the stress history and crustal architecture of the region where they occur.

On the Moon, rupes are widely distributed and can extend for tens to hundreds of kilometers. Notable examples include Rupes Recta, the Straight Wall, a well-known lunar rupes. On Mercury, large rupes such as Discovery Rupes reveal evidence of global contraction and shallow thrust faulting in the planet’s crust. Similar scarps have been identified on other planetary bodies, where the term rupes is used in official IAU mappings.

Rupes, as a formal nomenclature category, helps scientists study crustal structure, tectonic activity, and the thermal evolution of planetary surfaces. See also: rima, fossae, and other planetary surface features.