In planetary nomenclature, a tholus (pl. tholi ) is a small domical 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 transliterated the word into the Latin ''tholus,'' which means cupola or dome. 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. One justification for using neutral Latin or Greek descriptors was that it allowed features to be named and described before their geology or

geomorphology Geomorphology (from Ancient Greek: , ', "earth"; , ', "form"; and , ', "study") is the scientific study of the origin and evolution of topographic and bathymetric features created by physical, chemical or biological processes operating at or n ...

could be determined. 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 Vesta (minor-planet designation: 4 Vesta) is one of the largest objects in the asteroid belt, with a mean diameter of . It was discovered by the German astronomer Heinrich Wilhelm Matthias Olbers on 29 March 1807 and is named after Vesta, the ...

dwarf planet Ceres Ceres (; minor-planet designation: 1 Ceres) is a dwarf planet in the asteroid belt between the orbits of Mars and Jupiter. It was the first asteroid discovered, on 1 January 1801, by Giuseppe Piazzi at Palermo Astronomical Observatory in Sici ...

, and on Jupiter's moon Io. File:Tharsis Quadrangle map-la.svg, Map of the

Tharsis quadrangle The Tharsis quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Tharsis quadrangle is also referred to as MC-9 (Mars Chart-9). The name Tharsis refe ...

showing major features, several of which are tholi.

Tharsis Tharsis () is a vast volcanic plateau centered near the equator in the western hemisphere of Mars. The region is home to the largest volcanoes in the Solar System, including the three enormous shield volcanoes Arsia Mons, Pavonis Mons, and Asc ...

contains many volcanoes, including

Olympus Mons Olympus Mons (; Latin for Mount Olympus) is a large shield volcano on Mars. The volcano has a height of over 21.9 km (13.6 mi or 72,000 ft) as measured by the Mars Orbiter Laser Altimeter (MOLA). Olympus Mons is about two and a h ...

, the tallest known volcano in the Solar System. File:Ceraunius & Uranius tholi.jpg, ''

2001 Mars Odyssey ''2001 Mars Odyssey'' is a robotic spacecraft orbiting the planet Mars. The project was developed by NASA, and contracted out to Lockheed Martin, with an expected cost for the entire mission of US$297 million. Its mission is to use spectr ...

'' THEMIS mosaic of Ceraunius Tholus (lower volcano) and

Uranius Tholus Uranius Tholus is a volcano on Mars located in the Tharsis quadrangle at 26.52° north latitude and 262.43° east longitude. It is across with an elevation of and was named after a classical albedo feature name. Uranius Tholus is part of the Ur ...

(upper volcano). Ceraunius Tholus is about as high as Earth's Mount Everest. File:Jovis Tholus.jpg, Western part of

Jovis Tholus Jovis Tholus is a volcano in the Tharsis quadrangle of Mars located at 18.41° N and 117.41° W. It is 58.0 km across and was named after a classical albedo feature name. It has an elevation of . It has a 28 km diameter caldera of five crat ...

, as seen by THEMIS on Mars Odyssey spacecraft. Jovis Tholus is in the

Examples of tholi

Hecates Tholus Hecates Tholus is a Martian volcano, notable for results from the European Space Agency's Mars Express mission which indicate a major eruption took place 350 million years ago. The eruption created a caldera 10 km in diameter on the volcano's ...

Tharsis Tholus Tharsis Tholus is an intermediate-sized shield volcano located in the eastern Tharsis region of the planet Mars. The volcano was discovered by the Mariner 9 spacecraft in 1972 and originally given the informal name Volcano 7. In 1973, the In ...

References

External links

* Lists of named ''tholi''
on Venuson Marson Vestaon Io
Geology of Mars Volcanoes of Mars {{Geology-stub