Tholus

 ( Geology Of Mars ) 

In planetary nomenclature, a tholus (pl. tholi ) is a small dome mountain or hill. The word is from the Greek θόλος, tholos (pl. tholoi), which means a circular building with a conical or vaulted roof. The Romans the word into the Latin tholus, which means cupola or dome.Simpson, D.P. (1968). Cassell's New Latin Dictionary; Funk & Wagnalls: New York, p. 604. In 1973, the International Astronomical Union (IAU) adopted tholus as one of a number of official descriptor terms for topographic features on Mars and other planets and satellites.Greeley, R. (1994) Planetary Landscapes, 2nd ed.; Chapman & Hall: New York, pp. 35-36. One justification for using neutral Latin or Greek descriptors was that it allowed features to be named and described before their geology or geomorphology could be determined.Russell, J.F.; Snyder, C.W.; Kieffer, H.H. (1992). Origin and Use of Martian Nomenclature in Mars, H.H. Kieffer et al., Eds.; University of Arizona Press: Tucson, AZ, p. 1310. For example, many tholi appear to be volcanic in origin, but the term does not imply a specific geologic origin.Russell, J.F.; Snyder, C.W.; Kieffer, H.H. (1992). Origin and Use of Martian Nomenclature in Mars, H.H. Kieffer et al., Eds.; University of Arizona Press: Tucson, AZ, p. 1312. Currently (March 2015), the IAU recognizes 56 descriptor terms. (See Planetary nomenclature.) Tholi are present on Venus, Mars, asteroid 4 Vesta, dwarf planet Ceres, and on Jupiter moon Io.

== Gallery ==

• Hecates Tholus
• Tharsis Tholus

• Lists of named tholi: on Venus, on Mars, on Vesta, on Io