planetary nomenclature Planetary nomenclature, like terrestrial nomenclature, is a system of uniquely identifying features on the surface of a planet or natural satellite so that the features can be easily located, described, and discussed. Since the invention of the tel ...

, 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

transliterate Transliteration is a type of conversion of a text from one script to another that involves swapping letters (thus '' trans-'' + '' liter-'') in predictable ways, such as Greek → , Cyrillic → , Greek → the digraph , Armenian → or ...

d the word into the Latin ''tholus,'' which means

cupola In architecture, a cupola () is a relatively small, most often dome-like, tall structure on top of a building. Often used to provide a lookout or to admit light and air, it usually crowns a larger roof or dome. The word derives, via Italian, from ...

or dome. In 1973, the

International Astronomical Union The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreac ...

(IAU) adopted ''tholus'' as one of a number of official descriptor terms for topographic features on

Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury (planet), Mercury. In the English language, Mars is named for the Mars (mythology), Roman god of war. Mars is a terr ...

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 Geology () is a branch of natural science concerned with Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other Ear ...

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 Planetary nomenclature, like terrestrial nomenclature, is a system of uniquely identifying features on the surface of a planet or natural satellite so that the features can be easily located, described, and discussed. Since the invention of the tel ...

.) Tholi are present on

Venus Venus is the second planet from the Sun. It is sometimes called Earth's "sister" or "twin" planet as it is almost as large and has a similar composition. As an interior planet to Earth, Venus (like Mercury) appears in Earth's sky never fa ...

, 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, 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 The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar S ...

. 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 In Greek mythology and Ancient Greek religion, religion, Themis (; grc, Θέμις, Themis, justice, law, custom) is one of the twelve Titans, Titan children of Gaia and Uranus (mythology), Uranus, and the second wife of Zeus. She is the godde ...

mosaic of

Ceraunius Tholus Ceraunius Tholus is a volcano on Mars located in the Tharsis quadrangle at 24.25° north latitude and 262.75° east longitude, part of the Uranius group of volcanoes. It is across, approximately high and is named after a classical albedo featur ...

(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 Mount Everest (; Tibetan: ''Chomolungma'' ; ) is Earth's highest mountain above sea level, located in the Mahalangur Himal sub-range of the Himalayas. The China–Nepal border runs across its summit point. Its elevation (snow heig ...

. 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

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 spectro ...

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 I ...

References

External links

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