Planetary geology

Planetary geologist and NASA astronaut Harrison "Jack" Schmitt collecting lunar samples during the Apollo 17 mission in early-December 1972

Surface of Mars in a false-color photograph by the Viking 2 lander, December 9, 1977

European Space Agency Huygens in situ image from Titan's surface—the only image from the surface of a body farther away than Mars

Same image with contrast enhanced

Planetary geology, alternatively known as astrogeology or exogeology, is a planetary science discipline concerned with the geology of celestial bodies such as planets and their moons, asteroids, comets, and meteorites.^[1][2] 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. These investigations are centered around the composition, structure, processes, and history of a celestial body.^[3]

Planetary geology includes such topics as determining the properties and processes of 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 and compositions 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. Planetary geology largely applies concepts within the geosciences to planetary bodies in the broadest sense, and includes applications derived from fields in the geological sciences, such as geophysics and geochemistry.

History of planetary geology

Eugene Merle 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.^[4]

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.^{[citation needed]} 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!"^{[citation needed]}

Major centers for planetary science research include the Lunar and Planetary Institute, Applied Physics Laboratory, Planetary Science Institute, 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, California Institute of Technology, University of Colorado, Western Michigan University, Massachusetts Institute of Technology, and Washington University in St. Louis. Planetary geologists usually study either geology, astronomy, planetary science, geophysics, or one of the earth sciences at the graduate level.

Tools

Simulated interplanetary missions performed on Earth have studied procedures and tools for planetary geology. Various tools, including common archaeological tools such as hammers, shovels, brushes, were evaluated for use by planetary geologists.^[5] Along with these common tools, new advanced technologies have become available. These include spectroscopic databases, and data (such as mission logs, images and mapping) from previous unmanned interplanetary missions.^[6] Scientists use maps, images, telescopes on Earth, and orbiting telescopes (such as the Hubble Space Telescope).^[7] 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.^[8]

Features and terms

Main article: Planetary nomenclature

Planetary geology uses a wide variety of standardized descriptor names for features.^[9] All planetary feature names recognized by the International Astronomical Union (IAU) 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.^[10] This means that in some cases, names may change as new imagery becomes available,^[10] or in other cases widely adopted informal names changed in line with the rules.^[11] The standard names are chosen to consciously avoid interpreting the underlying cause of the feature, but rather to describe only its appearance.^[9]

Feature	Pronunciation[12]	Description	Designation
Albedo feature	/ælˈbiːdoʊ/	An area which shows a contrast in brightness or darkness (albedo) with adjacent areas. This term is implicit.	AL
Arcus, arcūs	/ˈɑːrkəs/	Arc: curved feature	AR
Astrum, astra	/ˈæstrəm/, /ˈæstrə/	Radial-patterned features on Venus	AS
Catena, catenae	/kəˈtiːnə/, /kəˈtiːni/	A chain of craters e.g. Enki Catena.	CA
Cavus, cavi	/ˈkeɪvəs/, /ˈkeɪvaɪ/	Hollows, irregular steep-sided depressions usually in arrays or clusters	CB
Chaos	/ˈkeɪɒs/	A distinctive area of broken or jumbled terrain e.g. Iani Chaos.	CH
Chasma, chasmata	/ˈkæzmə/, /ˈkæzmətə/	Deep, elongated, steep-sided depression e.g. Eos Chasma.	CM
Colles	/ˈkɒliːz/	A collection of small hills or knobs.	CO
Corona, coronae	/kɒˈroʊnə/, /kɒˈroʊni/	An oval feature. Used only on Venus and Miranda.	CR
Crater, craters	/ˈkreɪtər/	A circular depression likely created by impact event. This term is implicit.	AA
Dorsum, dorsa	/ˈdɔːrsəm/, /ˈdɔːrsə/	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	/ˈfækjʊlə/, /ˈfækjʊli/	Bright spot	FA
Farrum, farra	/ˈfærəm/, /ˈfærə/	Pancake-like structure, or a row of such structures. Used only on Venus.	FR
Flexus, flexūs	/ˈflɛksəs/	Very low curvilinear ridge with a scalloped pattern	FE
Fluctus, fluctūs	/ˈflʌktəs/	Terrain covered by outflow of liquid. Used on Venus, Io and Titan.	FL
Flumen, flumina	/ˈfluːmɪn/, /ˈfluːmɪnə/	Channel on Titan that might carry liquid	FM
Fossa, fossae	/ˈfɒsə/, /ˈfɒsi/	Long, narrow, shallow depression	FO
Fretum, freta	/ˈfriːtəm/, /ˈfriːtə/	Strait of liquid connecting two larger areas of liquid. Used only on Titan.	FT
Insula, insulae	/ˈɪnsjuːlə/, /ˈɪnsjuːli/	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	/ˈleɪbiːz/	Landslide debris. Used only on Mars.	LA
Labyrinthus, labyrinthi	/læbɪˈrɪnθəs/, /læbɪˈrɪnθaɪ/	Complex of intersecting valleys or ridges.	LB
Lacuna, lacunae	/ləˈkjuːnə/, /ləˈkjuːni/	Irregularly shaped depression having the appearance of a dry lake bed. Used only on Titan.	LU
Lacus, lacūs	/ˈleɪkəs/	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	/lɛnˈtɪkjʊlə/, /lɛnˈtɪkjʊli/	Small dark spots on Europa	LE
Linea, lineae	/ˈlɪniə/, /ˈlɪnii/	Dark or bright elongate marking, may be curved or straight	LI
Macula, maculae	/ˈmækjʊlə/, /ˈmækjʊli/	Dark spot, may be irregular	MA
Mare, maria	/ˈmɑːri, -reɪ/, /ˈmɑːriə/	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	/ˈmɛnsə/, /ˈmɛnsi/	A flat-topped prominence with cliff-like edges, i.e. a mesa.	MN
Mons, montes	/ˈmɒnz/, /ˈmɒntiːz/	Mons refers to a mountain. Montes refers to a mountain range.	MO
Oceanus	/oʊʃiːˈeɪnəs/	Very large dark area. The only feature with this designation is Oceanus Procellarum.	OC
Palus, paludes	/ˈpeɪləs/, /pəˈljuːdiːz/	"Swamp"; small plain. Used on the Moon and Mars.	PA
Patera, paterae	/ˈpætərə/, /ˈpætəri/	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	/pləˈnɪʃə/, /pləˈnɪʃi/	Low plain e.g. Amazonis Planitia.	PL
Planum, plana	/ˈpleɪnəm/, /ˈpleɪnə/	A plateau or high plain e.g. Planum Boreum.	PM
Plume		A cryovolcanic feature on Triton. This term is currently unused.	PU
Promontorium, promontoria	/prɒmənˈtɔːriəm/, /prɒmənˈtɔːriə/	"Cape"; headland. Used only on the Moon.	PR
Regio, regiones	/ˈriːdʒioʊ/ ~ /ˈrɛdʒioʊ/, /rɛdʒiˈoʊniːz/	Large area marked by reflectivity or color distinctions from adjacent areas, or a broad geographic region	RE
Reticulum, reticula	/rɪˈtɪkjʊləm/, /rɪˈtɪkjʊlə/	Reticular (netlike) pattern on Venus	RT
Rima, rimae	/ˈraɪmə/, /ˈraɪmi/	Fissure. Used only on the Moon.	RI
Rupes, rupes	/ˈruːpiːz/	Scarp	RU
Satellite feature		A feature that shares the name of an associated feature, for example Hertzsprung D.	SF
Scopulus, scopuli	/ˈskɒpjʊlə/, /ˈskɒpjʊlaɪ/	Lobate or irregular scarp	SC
Serpens, serpentes	/ˈsɜːrpɛnz/, /sərˈpɛntiːz/	Sinuous feature with segments of positive and negative relief along its length	SE
Sinus	/ˈsaɪnəs/	"Bay"; small plain on Moon or Mars, e.g. Sinus Meridiani; on Titan, bay within bodies of liquid.	SI
Sulcus, sulci	/ˈsʌlkəs/, /ˈsʌlsaɪ/	Subparallel furrows and ridges	SU
Terra, terrae	/ˈtɛrə/, /ˈtɛri/	Extensive land mass e.g. Arabia Terra, Aphrodite Terra.	TA
Tessera, tesserae	/ˈtɛsərə/, /ˈtɛsəri/	An area of tile-like, polygonal terrain. This term is used only on Venus.	TE
Tholus, tholi	/ˈθoʊləs/, /ˈθoʊlaɪ/	Small domical mountain or hill e.g. Hecates Tholus.	TH
Undae	/ˈʌndi/	A field of dunes. Used on Venus, Mars and Titan.	UN
Vallis, valles	/ˈvælɪs/, /ˈvæliːz/	A valley e.g. Valles Marineris.	VA
Vastitas, vastitates	/ˈvæstɪtəs/, /væstɪˈteɪtiːz/	An extensive plain. The only feature with this designation is Vastitas Borealis.	VS
Virga, virgae	/ˈvɜːrɡə/, /ˈvɜːrdʒi/	A streak or stripe of color. This term is currently used only on Titan.	VI

By planet

• Geological features of the Solar System
• Geological history of Earth
• Geology of Mercury
• Geology of Venus
• Geology of the Moon
• Geology of Mars
• Geology of Vesta
• Geology of Ceres
• Geology of Io
• Geology of Titan
• Geology of Triton
• Geology of Pluto
• Geology of Charon

See also

• Astrobiology – Science concerned with life in the universe
• Exoplanet – Planet outside the Solar System
• Exoplanetology
• Planetary habitability – Known extent to which a planet is suitable for life

References

1. James F. III, Bell; Campbell, Bruce A.; Robinson, Mark S. "What is planetary geology?". Cornell University. Archived from the original on Oct 25, 2015. Retrieved 6 October 2015.
2. "GEOL212: Planetary Geology". University of Maryland Department of Geology. Retrieved 6 October 2015.
3. McSween, Harry (11 July 2019). Planetary Geoscience (1 ed.). Cambridge University Press. pp. 3–19. ISBN 978-1107145382.
4. Chapman, Mary G. "Gene Shoemaker - Founder of Astrogeology". United States Geological Survey Astrogeology Science Center. Retrieved 21 May 2012.
5. Young, Kelsey; Hurtado, José M.; Bleacher, Jacob E.; Brent Garry, W.; Bleisath, Scott; Buffington, Jesse; Rice, James W. (2013-10-01). "Tools and technologies needed for conducting planetary field geology while on EVA: Insights from the 2010 Desert RATS geologist crewmembers". Acta Astronautica. NASA's 2010 Desert Research and Technology Studies Mission Objectives and Results. 90 (2): 332–343. Bibcode:2013AcAau..90..332Y. doi:10.1016/j.actaastro.2011.10.016. hdl:2060/20120012887. ISSN 0094-5765. S2CID 85509925.
6. "Planetary Science Tools". PDS Geoscience Node. Retrieved 2019-11-12.
7. "Astrogeology Science Center". United States Geological Survey. Retrieved 2019-11-12.
8. "Cartography and Imaging Sciences Node of NASA Planetary Data System". www.usgs.gov. Retrieved 2019-11-12.^{[permanent dead link‍]}
9. "Descriptor Terms (Feature Types)". Planetary Names. Retrieved 9 April 2018.
10. Morton, Oliver. Mapping Mars: science, imagination, and the birth of a world. Farrar, Straus, and Giroux, 2002.
11. "AAS Committee on the Status of Women" (PDF). American Astronomical Society. Archived from the original (PDF) on 14 March 2012. Retrieved 9 April 2018.
12. 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.

Further reading

• J. F. Bell III; B. A. Campbell; M. S. Robinson (2004). Remote Sensing for the Earth Sciences: Manual of Remote Sensing (3rd ed.). John Wiley & Sons. Archived from the original on Sep 16, 2016. Retrieved 2006-08-23.
• Roberge, Aki (1998-04-21). "The Planets After Formation". Department of Terrestrial Magnetism. Archived from the original on 2006-08-13. Retrieved 2006-08-23.
• Hauber E et al. (2019) Planetary geologic mapping. In: Hargitai H (ed ) Planetary Cartography and GIS. Springer.
• Hargitai H et al. (2015) Classification and Characterization of Planetary Landforms. In: Hargitai H, Kerszturi Á (eds) Encyclopedia of Planetary Landforms. Springer.
• Rossi, Angelo Pio; Gasselt, Stephan van, eds. (2018). Planetary Geology. Astronomy and Planetary Sciences. Springer International Publishing. ISBN 978-3-319-65177-4.