Enipeus Vallis
Encyclopedia
Enipeus Vallis is a valley in the northern hemisphere of the planet Mars
. It is centered at lat. 37°N, long. 267°E in the Arcadia quadrangle
(MC-3) between the large volcano Alba Mons and the Tempe Terra
plateau. The valley follows a gently sinuous
, north-south path for a distance of about 357 km (222 mi). It is likely an ancient watercourse
that formed during the early Hesperian (or late Noachian) period, around 3.7 billion years ago.
The valley is named after a river in Thessaly
, Greece
. Enipeus is also the name of a river god in classical mythology
. The International Astronomical Union
(IAU) formally adopted the name Enipeus Vallis in 1991. Vallis is the Latin word for valley.
. Valley networks are branching systems of valleys on Mars that superficially resemble terrestrial river drainage basin
s. They are abundant in the equatorial and southern highlands of the planet but less common in the northern hemisphere. Most valley networks are thought to have formed by flowing water, although the primary source of the water (melting ice, rainfall, springs) is still debated.
Enipeus Vallis is a single trunk valley, with no large tributaries. The valley is widest (about 10 km) at its southernmost reach near Lat. 33.6°N and rapidly tapers northward, maintaining a regular width of 3 to 5 km throughout most of its course. Above lat. 39.7°N the valley opens up, and drainage features become poorly integrated and ill-defined. North of this area, a somewhat subdued valley segment continues to the northwest from 40.5°N to about 42.5°N (northwest of the crater Lowbury) where it is locally buried by impact crater ejecta and young (Amazonian-aged) plains material. This northern valley segment gradually loses its identity amid the narrow graben
s of Tantalus Fossae
.
The elevation of the valley floor ranges from 885 m above datum (Mars "sea" level) in the south to 100 m or less in the north, where the northern segment of the valley begins to loose its definition. In cross-sectional profile, the valley is U-shaped
to rectangular, with depths ranging from 20 to 50 m. In the south, Enipeus Vallis has levee
-like ridges along its edges that are up to 20 m high. The levees are locally breached by lava flows from the surrounding plains.
In places, inner channels are visible along the valley floor. At around 36°N, the channels form an anastomosing (braided) pattern. Near the middle section of the southern valley segment, the valley divides into several branches, which then rejoin to form diamond-shaped islands. Faint longitudinal striations
and streamlined erosional bedform
s are common all along the floor of the valley. (See Photo Gallery.)
In fluvial
geomorphology
, a distinction is made between the terms stream valley
and stream channel
. Stream valleys are wide, elongate depressions. The stream itself flows within the confines of a channel in the center of the valley. A stream valley usually contains many channels. Channels are always much narrower and shallower than the valley that contains them, and water in the stream channel never comes close to filling the entire valley.
The distinction is important when discussing features of probable fluvial origin on Mars. Although Enipeus Vallis is described here as a valley, it has many features typical of a channel, including fluvial bedforms, streamlined features, a U-shaped profile, and levee deposits, which are always associated with channels not valleys. Except for its small width and general sinuosity
, Enipeus Vallis has characteristics resembling the immense Martian outflow channels
, which are true channels formed by the catastrophic release of large volumes of water. Fluvial landforms like Enipeus Vallis that show characteristics of both valley networks and outflow channels are relatively common on Mars (Ma'adim Vallis
, for example). and indicate that fluvial erosion on Mars has a distinctive genesis and evolution compared to Earth.
plateau in the Tempe-Mareotis region. The region lies on a broad topographic
shelf bounded by the higher elevations of Alba Mons to the west and Tempe Terra to the east. The region slopes gently to the north with a gradient of 0.3° or less. The area is characterized by abundant lava flows, low volcanic shields
, and small domes that are part of the Tempe Volcanic Province, a northeastern extension of the Tharsis Montes
chain of volcanoes. Although spatially related to the large Tharsis volcanoes, volcanism in the Tempe Volcanic Province has a different eruptive style and has been likened to the basalt
ic plains volcanism seen in Idaho
’s Snake River Plain
. This category of volcanic activity is intermediate between flood (plateau) basalts
and Hawaiian volcanism
.
The region is transected by numerous northeast-trending graben
s that form parts of the Tempe
, Mareotis
, and Tantalus Fossae
; these are fracture systems of varying ages that are oriented radially from the Tharsis
bulge. The region west of Enipeus Vallis is characterized by Hesperian-aged volcanic flows from Alba Mons. The area to the east consists of fractured and terraced highland plateaus of Noachian age. At the end of the Noachian period, these highland materials underwent an episode of fluvial
erosion and resurfacing. Enipeus Vallis probably formed during this fluvial episode.
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...
. It is centered at lat. 37°N, long. 267°E in the Arcadia quadrangle
Arcadia quadrangle
The Arcadia quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey Astrogeology Research Program. The quadrangle is located in the north-central portion of Mars’ western hemisphere and covers 240° to 300° east longitude and 30° to 65° north latitude...
(MC-3) between the large volcano Alba Mons and the Tempe Terra
Tempe Terra
Tempe Terra is a heavily cratered highland region in the northern hemisphere of the planet Mars. Located at the northeastern edge of the Tharsis volcanic province, Tempe Terra is notable for its high degree of crustal fracturing and deformation...
plateau. The valley follows a gently sinuous
Sinuosity
Sinuosity or sinuosity index is a measure of deviation of a path between two points from the shortest possible path...
, north-south path for a distance of about 357 km (222 mi). It is likely an ancient watercourse
Watercourse
A watercourse is any flowing body of water. These include rivers, streams, anabranches, and so forth.-See also:* physical geography* Environmental flow* Waterway* Hydrology* Wadi-External links:...
that formed during the early Hesperian (or late Noachian) period, around 3.7 billion years ago.
The valley is named after a river in Thessaly
Thessaly
Thessaly is a traditional geographical region and an administrative region of Greece, comprising most of the ancient region of the same name. Before the Greek Dark Ages, Thessaly was known as Aeolia, and appears thus in Homer's Odyssey....
, Greece
Greece
Greece , officially the Hellenic Republic , and historically Hellas or the Republic of Greece in English, is a country in southeastern Europe....
. Enipeus is also the name of a river god in classical mythology
Classical mythology
Classical mythology or Greco-Roman mythology is the cultural reception of myths from the ancient Greeks and Romans. Along with philosophy and political thought, mythology represents one of the major survivals of classical antiquity throughout later Western culture.Classical mythology has provided...
. The International Astronomical Union
International Astronomical Union
The International Astronomical Union IAU is a collection of professional astronomers, at the Ph.D. level and beyond, active in professional research and education in astronomy...
(IAU) formally adopted the name Enipeus Vallis in 1991. Vallis is the Latin word for valley.
General description
Enipeus Vallis is mapped as a valley networkValley networks (Mars)
Valley networks are branching networks of valleys on Mars that superficially resemble terrestrial river drainage basins. They are found mainly incised into the terrain of the martian southern highlands, and are typically - though not always - of Noachian age...
. Valley networks are branching systems of valleys on Mars that superficially resemble terrestrial river drainage basin
Drainage basin
A drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit of the basin, where the waters join another waterbody, such as a river, lake, reservoir, estuary, wetland, sea, or ocean...
s. They are abundant in the equatorial and southern highlands of the planet but less common in the northern hemisphere. Most valley networks are thought to have formed by flowing water, although the primary source of the water (melting ice, rainfall, springs) is still debated.
Enipeus Vallis is a single trunk valley, with no large tributaries. The valley is widest (about 10 km) at its southernmost reach near Lat. 33.6°N and rapidly tapers northward, maintaining a regular width of 3 to 5 km throughout most of its course. Above lat. 39.7°N the valley opens up, and drainage features become poorly integrated and ill-defined. North of this area, a somewhat subdued valley segment continues to the northwest from 40.5°N to about 42.5°N (northwest of the crater Lowbury) where it is locally buried by impact crater ejecta and young (Amazonian-aged) plains material. This northern valley segment gradually loses its identity amid the narrow graben
Graben
In geology, a graben is a depressed block of land bordered by parallel faults. Graben is German for ditch. Graben is used for both the singular and plural....
s of Tantalus Fossae
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 are called Fossae on Mars...
.
The elevation of the valley floor ranges from 885 m above datum (Mars "sea" level) in the south to 100 m or less in the north, where the northern segment of the valley begins to loose its definition. In cross-sectional profile, the valley is U-shaped
U-shaped valley
A U-shaped valley also known as a glacial trough is one formed by the process of glaciation. It has a characteristic U-shape, with steep, straight sides, and a flat bottom. Glaciated valleys are formed when a glacier travels across and down a slope, carving the valley by the action of scouring...
to rectangular, with depths ranging from 20 to 50 m. In the south, Enipeus Vallis has levee
Levee
A levee, levée, dike , embankment, floodbank or stopbank is an elongated naturally occurring ridge or artificially constructed fill or wall, which regulates water levels...
-like ridges along its edges that are up to 20 m high. The levees are locally breached by lava flows from the surrounding plains.
In places, inner channels are visible along the valley floor. At around 36°N, the channels form an anastomosing (braided) pattern. Near the middle section of the southern valley segment, the valley divides into several branches, which then rejoin to form diamond-shaped islands. Faint longitudinal striations
Striation (geology)
In geology, a striation means linear furrows generated from fault movement; The striation's direction reveal the movement directions in the fault plane. Similar striations can occur with glaciation....
and streamlined erosional bedform
Bedform
A bedform is a depositional feature on the bed of a river or other body of flowing water that is formed by the movement of the bed material due to the flow. Bedforms are characteristic to the flow parameters, and are particularly to flow depth and velocity, and therefore the Froude...
s are common all along the floor of the valley. (See Photo Gallery.)
In fluvial
Fluvial
Fluvial is used in geography and Earth science to refer to the processes associated with rivers and streams and the deposits and landforms created by them...
geomorphology
Geomorphology
Geomorphology is the scientific study of landforms and the processes that shape them...
, a distinction is made between the terms stream valley
River Valley
River Valley is the name of an urban planning area within the Central Area, Singapore's central business district.The River Valley Planning Area is defined by the region bounded by Orchard Boulevard, Devonshire Road and Eber Road to the north, Oxley Rise and Mohamed Sultan Road to the east, Martin...
and stream channel
Stream channel
Stream channel is the physical confine of a stream consisting of a bed and stream banks.Stream channels exist in a variety of geometries. The stream channel development is controlled by both water and sediment movement. There is a difference between low gradient streams and high gradient streams...
. Stream valleys are wide, elongate depressions. The stream itself flows within the confines of a channel in the center of the valley. A stream valley usually contains many channels. Channels are always much narrower and shallower than the valley that contains them, and water in the stream channel never comes close to filling the entire valley.
The distinction is important when discussing features of probable fluvial origin on Mars. Although Enipeus Vallis is described here as a valley, it has many features typical of a channel, including fluvial bedforms, streamlined features, a U-shaped profile, and levee deposits, which are always associated with channels not valleys. Except for its small width and general sinuosity
Sinuosity
Sinuosity or sinuosity index is a measure of deviation of a path between two points from the shortest possible path...
, Enipeus Vallis has characteristics resembling the immense Martian outflow channels
Outflow channels
Outflow channels is the term used to describe extremely long, wide swathes of scoured ground on Mars, commonly containing the streamlined remnants of pre-existing topography and other linear erosive features indicating sculpting by fluids moving downslope...
, which are true channels formed by the catastrophic release of large volumes of water. Fluvial landforms like Enipeus Vallis that show characteristics of both valley networks and outflow channels are relatively common on Mars (Ma'adim Vallis
Ma'adim Vallis
Ma'adim Vallis is one of the largest outflow channels on Mars, about 700 km long and significantly larger than Earth's Grand Canyon. It is over 20 km wide and 2 km deep in some places. It runs from a region of southern lowlands thought to have once contained a large group of lakes ...
, for example). and indicate that fluvial erosion on Mars has a distinctive genesis and evolution compared to Earth.
Regional geology
Enipeus Vallis is located at the western edge of the Tempe TerraTempe Terra
Tempe Terra is a heavily cratered highland region in the northern hemisphere of the planet Mars. Located at the northeastern edge of the Tharsis volcanic province, Tempe Terra is notable for its high degree of crustal fracturing and deformation...
plateau in the Tempe-Mareotis region. The region lies on a broad topographic
Topography
Topography is the study of Earth's surface shape and features or those ofplanets, moons, and asteroids...
shelf bounded by the higher elevations of Alba Mons to the west and Tempe Terra to the east. The region slopes gently to the north with a gradient of 0.3° or less. The area is characterized by abundant lava flows, low volcanic shields
Shield volcano
A shield volcano is a type of volcano usually built almost entirely of fluid lava flows. They are named for their large size and low profile, resembling a warrior's shield. This is caused by the highly fluid lava they erupt, which travels farther than lava erupted from more explosive volcanoes...
, and small domes that are part of the Tempe Volcanic Province, a northeastern extension of the Tharsis Montes
Tharsis Montes
The Tharsis Montes are three large shield volcanoes in the Tharsis region of the planet Mars. From north to south, the volcanoes are Ascraeus Mons, Pavonis Mons and Arsia Mons. Mons is the Latin word for mountain...
chain of volcanoes. Although spatially related to the large Tharsis volcanoes, volcanism in the Tempe Volcanic Province has a different eruptive style and has been likened to the basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...
ic plains volcanism seen in Idaho
Idaho
Idaho is a state in the Rocky Mountain area of the United States. The state's largest city and capital is Boise. Residents are called "Idahoans". Idaho was admitted to the Union on July 3, 1890, as the 43rd state....
’s Snake River Plain
Snake River Plain
The Snake River Plain is a geologic feature located primarily within the state of Idaho in the United States of America. It stretches about westward from northwest of the state of Wyoming to the Idaho-Oregon border. The plain is a wide flat bow-shaped depression, and covers about a quarter of Idaho...
. This category of volcanic activity is intermediate between flood (plateau) basalts
Flood basalt
A flood basalt or trap basalt is the result of a giant volcanic eruption or series of eruptions that coats large stretches of land or the ocean floor with basalt lava. Flood basalts have occurred on continental scales in prehistory, creating great plateaus and mountain ranges...
and Hawaiian volcanism
Hawaiian eruption
A Hawaiian eruption is a type of volcanic eruption where lava flows from the vent in a relative gentle, low level eruption, so called because it is characteristic of Hawaiian volcanoes. Typically they are effusive eruptions, with basaltic magmas of low viscosity, low content of gases, and high...
.
The region is transected by numerous northeast-trending graben
Graben
In geology, a graben is a depressed block of land bordered by parallel faults. Graben is German for ditch. Graben is used for both the singular and plural....
s that form parts of the Tempe
Tempe Fossae
Tempe Fossae is a group of troughs in the Arcadia quadrangle of Mars, located at 40.2° north latitude and 71.4° west longitude. It is about 2,000 km long and was named after an albedo feature at 40N, 70W. Troughs, like this one are called Fossae on Mars. More information and more examples...
, Mareotis
Mareotis Fossae
Mareotis Fossae is a group of 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. Troughs, like this one are called Fossae on Mars. More information and more examples...
, and Tantalus Fossae
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 are called Fossae on Mars...
; these are fracture systems of varying ages that are oriented radially from the Tharsis
Tharsis
The Tharsis region on Mars is a vast volcanic plateau centered near the equator in Mars’ western hemisphere. The region is home to the largest volcanoes in the Solar System, including the three enormous shield volcanoes Arsia Mons, Pavonis Mons, and Ascraeus Mons, which are collectively known as...
bulge. The region west of Enipeus Vallis is characterized by Hesperian-aged volcanic flows from Alba Mons. The area to the east consists of fractured and terraced highland plateaus of Noachian age. At the end of the Noachian period, these highland materials underwent an episode of fluvial
Fluvial
Fluvial is used in geography and Earth science to refer to the processes associated with rivers and streams and the deposits and landforms created by them...
erosion and resurfacing. Enipeus Vallis probably formed during this fluvial episode.
Reference
- JMARS. http://jmars.asu.edu/. (See Christensen, P.; Gorelick, N.; Anwar, S.; Dickenshied, S.; Edwards, C.; Engle, E. (2007) “New Insights About Mars From the Creation and Analysis of Mars Global Datasets;” American Geophysical Union, Fall Meeting, abstract #P11E-01. http://adsabs.harvard.edu/abs/2007AGUFM.P11E..01C.)