Planetary geology, alternatively known as astrogeology or exogeology, is a planetary science discipline concerned with the geology of the celestial bodies such as the planets and their moons, asteroids, comets, and meteorites. Although the geo- prefix typically indicates topics of or relating to Earth, planetary geology is named as such for historical and convenience reasons; due to the types of investigations involved, it is closely linked with Earth-based geology.
Planetary geology includes such topics as determining the internal structure of the terrestrial planets, and also looks at planetary volcanism and surface processes such as impact craters, fluvial and aeolian processes. The structures of the giant planets and their moons are also examined, as is the make-up of the minor bodies of the Solar System, such as asteroids, the Kuiper Belt, and comets.
History of planetary geologyEdit
The examples and perspective in this section deal primarily with the United States and do not represent a worldwide view of the subject. (January 2014) (Learn how and when to remove this template message)
Eugene Shoemaker is credited with bringing geologic principles to planetary mapping and creating the branch of planetary science in the early 1960s, the Astrogeology Research Program, within the United States Geological Survey. He made important contributions to the field and the study of impact craters, Selenography (study of the Moon), asteroids, and comets.
Today many institutions are concerned with the study and communication of planetary sciences and planetary geology. The Visitor Center at Barringer Meteor Crater near Winslow, Arizona includes a museum of planetary geology. The Geological Society of America's Planetary Geology Division has been growing and thriving since May 1981 and has two mottos: "One planet just isn't enough!" and "“The GSA Division with the biggest field area!"
Major centers for planetary science research include the Lunar and Planetary Institute, the Applied Physics Laboratory, the Planetary Science Institute, the Jet Propulsion Laboratory, Southwest Research Institute, and Johnson Space Center. Additionally, several universities conduct extensive planetary science research, including Montana State University, Brown University, the University of Arizona, Caltech, the University of Colorado, Western Michigan University, MIT, and Washington University in St. Louis.
Several tools been used in planetary geology, including common archaeological tools such as hammers, shovels, brushes, etc. are often used by planetary geologists. Along with these common tools, new advanced technologies are used by planetary geologists Scientists also with these tools, use maps and images that telescopes on Earth (thirty meter telescope) and orbiting telescopes (Hubble) have taken different planetary bodies. The maps and images are stored in the NASA Planetary Data System where tools such as the Planetary Image Atlas help to search for certain items such as geological features including: mountains, ravines, and craters.
Features and termsEdit
Planetary geology uses a wide variety of standardized descriptor names for features. All planetary feature names recognized by the International Astronomical Union combine one of these names with a possibly unique identifying name. The conventions which decide the more precise name are dependent on which planetary body the feature is on, but the standard descriptors are in general common to all astronomical planetary bodies. Some names have a long history of historical usage, but new must be recognized by the IAU Working Group for Planetary System Nomenclature as features are mapped and described by new planetary missions. This means that in some cases names may change as new imagery becomes available, or in other cases widely adopted informal names changed in line with the rules. The standard names are chosen to consciously avoid interpreting the underlying cause of the feature, but rather to describe only its appearance.
|Albedo feature||//||An area which shows a contrast in brightness or darkness (albedo) with adjacent areas. This term is implicit.||AL|
|Arcus, arcūs||//||Arc: curved feature||AR|
|Astrum, astra||//, //||Radial-patterned features on Venus||AS|
|Catena, catenae||//, //||A chain of craters e.g. Enki Catena.||CA|
|Cavus, cavi||//, //||Hollows, irregular steep-sided depressions usually in arrays or clusters||CB|
|Chaos||//||A distinctive area of broken or jumbled terrain e.g. Iani Chaos.||CH|
|Chasma, chasmata||//, //||Deep, elongated, steep-sided depression e.g. Eos Chasma.||CM|
|Colles||//||A collection of small hills or knobs.||CO|
|Corona, coronae||//, //||An oval feature. Used only on Venus and Miranda.||CR|
|Crater, craters||//||A circular depression likely created by impact event. This term is implicit.||AA|
|Dorsum, dorsa||//, //||Ridge, sometimes called a wrinkle ridge e.g. Dorsum Buckland.||DO|
|Eruptive center||An active volcano on Io. This term is implicit.||ER|
|Facula, faculae||//, //||Bright spot||FA|
|Farrum, farra||//, //||Pancake-like structure, or a row of such structures. Used only on Venus.||FR|
|Flexus, flexūs||//||Very low curvilinear ridge with a scalloped pattern||FE|
|Fluctus, fluctūs||//||Terrain covered by outflow of liquid. Used on Venus, Io and Titan.||FL|
|Flumen, flumina||//, //||Channel on Titan that might carry liquid||FM|
|Fossa, fossae||//, //||Long, narrow, shallow depression||FO|
|Fretum, freta||//, //||Strait of liquid connecting two larger areas of liquid. Used only on Titan.||FT|
|Insula, insulae||//, //||Island (islands), an isolated land area (or group of such areas) surrounded by, or nearly surrounded by, a liquid area (sea or lake). Used only on Titan.||IN|
|Labes, labes||//||Landslide debris. Used only on Mars.||LA|
|Labyrinthus, labyrinthi||//, //||Complex of intersecting valleys or ridges.||LB|
|Lacuna, lacunae||//, //||Irregularly shaped depression having the appearance of a dry lake bed. Used only on Titan.||LU|
|Lacus, lacūs||//||A "lake" or small plain on Moon and Mars; on Titan, a "lake" or small, dark plain with discrete, sharp boundaries.||LC|
|Landing site name||Lunar features at or near Apollo landing sites||LF|
|Large ringed feature||Cryptic ringed features||LG|
|Lenticula, lenticulae||//, //||Small dark spots on Europa||LE|
|Linea, lineae||//, //||Dark or bright elongate marking, may be curved or straight||LI|
|Macula, maculae||//, //||Dark spot, may be irregular||MA|
|Mare, maria||/ - /,, //||A "sea" or large circular plain on Moon and Mars, e.g. Mare Erythraeum; on Titan, large expanses of dark materials thought to be liquid hydrocarbons, e.g. Ligeia Mare.||ME|
|Mensa, mensae||//, //||A flat-topped prominence with cliff-like edges, i.e. a mesa.||MN|
|Mons, montes||//, //||Mons refers to a mountain. Montes refers to a mountain range.||MO|
|Oceanus||//||Very large dark area. The only feature with this designation is Oceanus Procellarum.||OC|
|Palus, paludes||//, //||"Swamp"; small plain. Used on the Moon and Mars.||PA|
|Patera, paterae||//, //||Irregular crater, or a complex one with scalloped edges e.g. Ah Peku Patera. Usually refers to the dish-shaped depression atop a volcano.||PE|
|Planitia, planitiae||//, //||Low plain e.g. Amazonis Planitia.||PL|
|Planum, plana||//, //||A plateau or high plain e.g. Planum Boreum.||PM|
|Plume||A cryovolcanic feature on Triton. This term is currently unused.||PU|
|Promontorium, promontoria||//, //||"Cape"; headland. Used only on the Moon.||PR|
|Regio, regiones||// ~ //, //||Large area marked by reflectivity or color distinctions from adjacent areas, or a broad geographic region||RE|
|Reticulum, reticula||//, //||reticular (netlike) pattern on Venus||RT|
|Rima, rimae||//, //||Fissure. Used only on the Moon.||RI|
|Satellite feature||A feature that shares the name of an associated feature, for example Hertzsprung D.||SF|
|Scopulus, scopuli||//, //||Lobate or irregular scarp||SC|
|Serpens, serpentes||//, //||Sinuous feature with segments of positive and negative relief along its length||SE|
|Sinus||//||"Bay"; small plain on Moon or Mars, e.g. Sinus Meridiani; On Titan, bay within bodies of liquid.||SI|
|Sulcus, sulci||//, //||Subparallel furrows and ridges||SU|
|Terra, terrae||//, //||Extensive land mass e.g. Arabia Terra, Aphrodite Terra.||TA|
|Tessera, tesserae||//, //||An area of tile-like, polygonal terrain. This term is used only on Venus.||TE|
|Tholus, tholi||//, //||Small domical mountain or hill e.g. Hecates Tholus.||TH|
|Undae||//||A field of dunes. Used on Venus, Mars and Titan.||UN|
|Vallis, valles||//, //||A valley e.g. Valles Marineris.||VA|
|Vastitas, vastitates||//, //||An extensive plain. The only feature with this designation is Vastitas Borealis.||VS|
|Virga, virgae||//, //||A streak or stripe of color. This term is currently used only on Titan.||VI|
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- Listed pronunciations are conventional or follow the traditional English pronunciation of Latin words. However, some speakers use different (often variable) pronunciations that are closer to the Latin or Greek.
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