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 fossa (pl. fossae ) is a long, narrow depression (trough) on the surface of an extraterrestrial body, such as a planet or moon. The term, which means "ditch" or "trench" in

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

, is not a geological term as such but a descriptor term used by the

United States Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...

(USGS) and 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) for topographic features whose geology or geomorphology is uncertain due to lack of data or knowledge of the exact processes that formed them. Fossae are believed to be the result of a number of geological processes, such as

faulting In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...

subsidence Subsidence is a general term for downward vertical movement of the Earth's surface, which can be caused by both natural processes and human activities. Subsidence involves little or no horizontal movement, which distinguishes it from slope move ...

. Many fossae on Mars are probably

graben In geology, a graben () is a depressed block of the crust of a planet or moon, bordered by parallel normal faults. Etymology ''Graben'' is a loan word from German, meaning 'ditch' or 'trench'. The word was first used in the geologic contex ...

On Mars

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 ...

is home to large troughs (long narrow depressions) called fossae in the geographical language used for Mars. This term is derived from Latin; therefore fossa is singular and fossae is plural. Troughs form when the crust is stretched until it breaks. The stretching can be due to the large weight of a nearby volcano. Studies have shown that the volcanoes of Tharsis caused most of the major fossae on Mars. The stress that caused the fossae and other tectonic features is centered in

Noctis Labyrinthus Noctis Labyrinthus () is a region of Mars located in the Phoenicis Lacus quadrangle, between Valles Marineris and the Tharsis upland. The region is notable for its maze-like system of deep, steep-walled valleys. The valleys and canyons of this ...

, at 4 S and 253 E. But the center has moved somewhat over time. Fossae/pit craters are common near volcanoes in the Tharsis and Elysium system of volcanoes. A trough often has two breaks with a middle section moving down, leaving steep cliffs along the sides; such a trough is called a graben. Lake George, in northern

New York State New York, officially the State of New York, is a state in the Northeastern United States. It is often called New York State to distinguish it from its largest city, New York City. With a total area of , New York is the 27th-largest U.S. stat ...

, is a lake that sits in a graben. Sometimes, a line of pits form as material collapse into a void that results from the stretching. Pit craters do not have rims or ejecta around them, like impact craters do. Studies have found that on Mars a fault may be as deep as 5 km, that is the break in the rock goes down to 5 km. Moreover, the crack or fault sometimes widens or dilates. This widening causes a void to form with a relatively high volume. When material slides into the void, a pit crater or a pit crater chain forms. On Mars, individual pit craters can join to form chains or even to form troughs that are sometimes scalloped.Wyrick, D., D. Ferrill, D. Sims, and S. Colton. 2003. Distribution, Morphology and Structural Associations of Martian Pit Crater Chains. Lunar and Planetary Science XXXIV (2003) Other ideas have been suggested for the formation of fossae and pit craters. There is evidence that they are associated with dikes of magma. Magma might move along, under the surface, breaking the rock and more importantly melting ice. The resulting action would cause a crack to form at the surface. Dikes caused both by tectonic stretching (extension) and by dikes are found in

Iceland Iceland ( is, Ísland; ) is a Nordic island country in the North Atlantic Ocean and in the Arctic Ocean. Iceland is the most sparsely populated country in Europe. Iceland's capital and largest city is Reykjavík, which (along with its s ...

. Pit craters are not common on Earth.

Sinkholes A sinkhole is a depression or hole in the ground caused by some form of collapse of the surface layer. The term is sometimes used to refer to doline, enclosed depressions that are locally also known as ''vrtače'' and shakeholes, and to openi ...

, where the ground falls into a hole (sometimes in the middle of a town) resemble pit craters on Mars. However, on the Earth these holes are caused by limestone being dissolved thereby causing a void. Knowledge of the locations and formation mechanisms of pit craters and fossae is important for the future colonization of Mars because they may be reservoirs of water.Ferrill, D., D. Wyrick, A. Morris, D. Sims, and N. Franklin. 2004. Dilational fault slip and pit chain formation on Mars 14:10:4-12

Tharsis quadrangle

Image:Tharsis Quadrangle map-la.svg, Map of

with major features indicated. Tharsis 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 ...

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 ...

, although it looks small, 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 ...

. The locations of some fossae are shown. Image:Pit chain in Tractus Fossae Tharsis.JPG, Trough in the Tractus Fossae caused by faults and resulting collapse of material into faults forming a chain of pits, as seen by

Mars Global Surveyor ''Mars Global Surveyor'' (MGS) was an American robotic space probe developed by NASA's Jet Propulsion Laboratory and launched November 1996. MGS was a global mapping mission that examined the entire planet, from the ionosphere down through the a ...

. Image is located in Tharsis quadrangle. Image:Tractus Fossae Ringed Pit.JPG, A ringed pit in the Tractus Fossae, as seen by

HiRISE High Resolution Imaging Science Experiment is a camera on board the ''Mars Reconnaissance Orbiter'' which has been orbiting and studying Mars since 2006. The 65 kg (143 lb), US$40 million instrument was built under the direction o ...

. Image is located in

. Scale bar is 1000 m. Image:Ceraunius Fossae.JPG, The

Ceraunius Fossae The Ceraunius Fossae are a set of fractures in the northern Tharsis region of Mars. They lie directly south of the large volcano Alba Mons and consist of numerous parallel faults and tension cracks that deform the ancient highland crust.Carr, M.H ...

, as seen by HiRISE. Image is located in

. Image:Olympica Fossae.JPG, The

Olympica Fossae The Olympica Fossae are a set of troughs in the Tharsis quadrangle of Mars at 25° north latitude and 114.1° west longitude. They are about 420 km long and were named after an albedo feature at 17N, 134W. Parts of the fossae have been sugg ...

, as seen by HiRISE. Click on image to see rock layers in wall. Image is located in

Arcadia quadrangle

Image:Arcadia Map.JPG, Map of

Arcadia quadrangle The Arcadia quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The quadrangle is located in the north-central portion of Mars’ western hemisphere and ...

with major features labeled. Several large fossae are indicated on the map Image:Alba Patera.JPG, Graben near

Alba Patera Alba Mons (formerly and still occasionally known as Alba Patera, a term that has since been restricted to the volcano's summit caldera; also initially known as the Arcadia ring) is a volcano located in the northern Tharsis region of the planet Ma ...

Graben In geology, a graben () is a depressed block of the crust of a planet or moon, bordered by parallel normal faults. Etymology ''Graben'' is a loan word from German, meaning 'ditch' or 'trench'. The word was first used in the geologic contex ...

and catenae, collapse features, both caused by faults. When the crust is stretched, faults form and material falls into voids created by the stretching. Uranius Tholus (upper) and Ceraunius Tholus (largest)

volcanoes A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates are ...

are visible in wide context view, below and to the right of Alba Patera. Image is located in

. Image taken with

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 ...

Image:Cross cutting grabens in Arcadia.JPG, Forces from different directions caused this complex of

s to form. Image is located in Arcadia quadrangle. Image taken with THEMIS Image:Mareotis Fossae Region.JPG,

Mareotis Fossae Mareotis Fossae is a group of fossae (troughs) in the Arcadia quadrangle of Mars, located at 44° north latitude and 75.3° west longitude. It is about 1,860 km long and was named after an albedo feature at 32N, 96W. Image:Mareotis Fossae ...

Region, as seen by HiRISE. Image is located in Arcadia quadrangle Image:Tantalus Fossae.JPG,

Tantalus Fossae Tantalus Fossae is a group of troughs in the Arcadia quadrangle of Mars, located at 50.9° north latitude and 97.5° west longitude. They are about 2,400 km long and was named after an albedo feature at 35N, 110W. Troughs like this one a ...

, as seen by HiRISE. Click on image to see dust devil tracks. Image is located in Arcadia quadrangle

Elysium quadrangle

Image:Elysium map.JPG, Map of

Elysium quadrangle The Elysium quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Elysium quadrangle is also referred to as MC-15 (Mars Chart-15). The name Elysium r ...

Elysium Mons Elysium Mons is a volcano on Mars located in the volcanic province Elysium, at , in the Martian eastern hemisphere. It stands about above its base, and about above the Martian ''datum'', making it the third tallest Martian mountain in terms o ...

and Albor Tholus are large volcanoes; locations of large fossae are indicated Image:Cerberus Fossae with HiRISE.JPG, The

Cerberus Fossae The Cerberus Fossae are a series of semi-parallel fissures on Mars formed by faults which pulled the crust apart in the Cerberus region. They are 1235 km across and centered at 11.28 °N and 166.37 °E. Their northernmost latitude is 16.16 ...

in the Elysium quadrangle, as seen by HiRISE (scale bar is 1.0 km) Image:Elysium Fossae.JPG, The Elysium Fossae in Elysium quadrangle, as seen by HiRISE (scale bar is 500 m) Image:Troughs in Elysium Planitia.JPG, Troughs to the east of Albor Tholus, as seen by HiRISE under the HiWish program. Image:Troughs showing blue in Elysium Planitia.JPG, Portion of a trough (fossa) in

Elysium Planitia Elysium Planitia, located in the Elysium and Aeolis quadrangles, is a broad plain that straddles the equator of Mars, centered at . It lies to the south of the volcanic province of Elysium, the second largest volcanic region on the planet, a ...

, as seen by HiRISE under the HiWish program (blue indicates probably seasonal frost)

Mare Tyrrhenum quadrangle

Image:Mare Tyrrhenum map.JPG, Map of

Mare Tyrrhenum quadrangle The Mare Tyrrhenum quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. This quadrangle is also referred to as MC-22 (Mars Chart-22). It contains parts o ...

. Tyrrhena Patera is a major

volcano A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates are ...

with pit craters. Image:Tyrrhena Patera.JPG,

Tyrrhena Patera Tyrrhenus Mons, formerly Tyrrhena Mons or Tyrrhena Patera, is a large volcano in the Mare Tyrrhenum quadrangle of Mars, located at 21.36° south latitude and 253.47° west longitude. The name "Tyrrhena Patera" now refers only to the central depres ...

, as seen by HiRISE and suggested by Ehsan Sanaei's high school astronomy club in Yazd, Iran. Click on image to see excellent view of pit crater chains and concentric features around a volcano.

Memnonia quadrangle

Image:Graben in Memnonia Fossae.JPG, Graben in Memnonia Fossae, as seen by HiRISE. This graben is believed to be the result of magmatic dikes rather than regional tectonic stretching. The scale bar is 1000 meters long.

Phoenicus Lacus quadrangle

Image:Oti Fossae.JPG, Oti Fossae in the

Phoenicis Lacus quadrangle The Phoenicis Lacus quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Phoenicis Lacus quadrangle is also referred to as MC-17 (Mars Chart-17). P ...

, as seen by HiRISE. Image:Oti Fossae.jpg, Oti Fossae, as seen by THEMIS. These parallel graben are found on the northeastern side of Arsia Mons; they are in line with the NE/SW trend of the three volcanoes in Tharsis. Image:Oti Fossae Close-up.JPG, Oti Fossae, as seen by THEMIS. These parallel graben are found on the northeastern side of Arsia Mons; they are in line with the NE/SW trend of the three volcanoes in Tharsis.

Diacria quadrangle

Image:Cyane Fossae.JPG, Cyane Fossae in the

Diacria quadrangle The Diacria quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The quadrangle is located in the northwestern portion of Mars’ western hemisphere and co ...

, as seen by HiRISE.

Phaethontis quadrangle

Image:Icaria Fossae Graben.JPG, Icaria Fossae Graben in the

Phaethontis quadrangle The Phaethontis quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Phaethontis quadrangle is also referred to as MC-24 (Mars Chart-24). The name com ...

, as seen by HiRISE. Click on image for a better view of

Dust Devil Tracks Martian dust devils (dust devils on Mars) were first photographed by the Viking orbiters in the 1970s. In 1997, the Mars Pathfinder lander detected a dust devil passing over it. In the first image below, photographed by the Mars Global Surveyor, ...

. Image:Context image for gullies in crater and trough.JPG, MOLA context image for the series of three images to follow of gullies in a trough and nearby crater. This image shows where the image is in relation to Mariner Crater and Sirenum Fossae. Image:Gullies in trough and crater.jpg, Gullies in a trough and nearby crater, as seen by HiRISE under the

HiWish program HiWish is a program created by NASA so that anyone can suggest a place for the HiRISE camera on the Mars Reconnaissance Orbiter to photograph. It was started in January 2010. In the first few months of the program 3000 people signed up to use HiRIS ...

. Scale bar is 500 meters long. Image:Gullies in trough.JPG, Close-up of gullies in trough, as seen by HiRISE under the HiWish program. These are some of the smaller gullies visible on Mars.

Ismenius Lacus quadrangle

Image:Coloe Fossae.JPG, Coloe Fossae

Dike Dyke (UK) or dike (US) may refer to: General uses * Dyke (slang), a slang word meaning "lesbian" * Dike (geology), a subvertical sheet-like intrusion of magma or sediment * Dike (mythology), ''Dikē'', the Greek goddess of moral justice * Dikes ...

s and/or faults, as seen by HiRISE. Dikes and faults may have produced mineral deposits. Coloe Fossae is in the

Ismenius Lacus quadrangle The Ismenius Lacus quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The quadrangle is located in the northwestern portion of Mars’ eastern hemisphere ...

. Image:Coloe Fossae Lineated Valley Fill.JPG, Coloe Fossae lineated valley fill, as seen by HiRISE. Coloe Fossae is in the Ismenius Lacus quadrangle. Scale bar is 500 meters long. Image:Cole Fossae Pits.JPG, Coloe Fossae Pits, as seen by HiRISE. Pits are believed to result from escaping water. Coloe Fossae is in the Ismenius Lacus quadrangle.

Cebrenia quadrangle

Image:Galaxias Fossae Trough.JPG, Galaxias Fossae Trough, as seen by HiRISE. Image in the

Cebrenia quadrangle The Cebrenia quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The quadrangle is located in the northeastern portion of Mars’ eastern hemisphere and ...

. Image:Hephaestus Fossae Two Vews.JPG,

Hephaestus Fossae The Hephaestus Fossae are a system of troughs and channels in the Amenthes quadrangle of Mars, with a location centered at 21.1 N and 237.5 W. They are 604 km long and were named after a classical albedo feature name. The fossae have been te ...

: two views, as seen by HiRISE. Picture on right lies to the top (north) of other picture. Fossa (geology) often form by material moving into an underground void. Image located in Cebrenia quadrangle.

Lunae Palus quadrangle

Image:Labeatis Fossae.jpg, Labeatis Fossae, as seen by THEMIS. Labeatis Fossae is in the

Lunae Palus quadrangle The Lunae Palus quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The quadrangle is also referred to as MC-10 (Mars Chart-10). Lunae Planum and parts o ...

. Image:Labeatis Fossae Close-up.JPG, Close-up view of Labeatis Fossae, as seen by THEMIS. Labeatis Fossae is in the

Amenthes quadrangle

Image:ESP_024921fan.jpg, Wall of

Amenthes Fossae The Amenthes Fossae are a system of troughs in the Amenthes quadrangle of Mars centered at 9.07°N and 102.68°E. They are 850 km across and were named after a classical albedo feature. The classical albedo feature name was based on the Eg ...

, as seen by HiRISE under

. Image:ESP 036801 2015amenthespits.jpg, Large pits, as seen by HiRISE under HiWish program Image:ESP 036023 2025amenthestroughtop.jpg, Trough, as seen by HiRISE under HiWish program Image:Hephaestus Fossae Two Vews.JPG,

Two Views, as seen by HiRISE. Picture on right lies to the top (north) of other picture. Fossa (geology) often form by material moving into an underground void. ESP 051781 2035troughs.jpg, Troughs, as seen by HiRISE under HiWish program

References

External resources

Fossae on Mars

Fossae on Venus

Fossae on the Moon

Fossae on Enceladus

Fossae on Ganymede
{{DEFAULTSORT:Fossa (Geology) Surface features of bodies of the Solar System