Anseris Mons
Encyclopedia
Anseris Mons is an isolated massif
(mountain) in the southern highlands of Mars
, located at the northeastern edge of Hellas Planitia
at longitude 86.6°E and latitude 29.81°S. The mountain is 58 km (36 mi) in diameter and rises to an elevation of approximately 4,200 m (13,780 ft) above datum (martian “sea” level) or about 6,200 m (20,300 ft) above the surrounding plains. The mountain lies in the southeastern quarter of the Iapygia quadrangle
(MC-21), straddling the boundary with the adjoining Hellas quadrangle
(MC-28) to the south.
Anseris Mons is named from Anseris Fons, a telescopic albedo feature
mapped by Greek astronomer E. M. Antoniadi in 1930. The name was approved by the International Astronomical Union
(IAU) in 1991.
Anseris Mons is not a volcano. Geologically, the massif is thought to be the eroded remnant of an ancient crustal block uplifted from depths of several kilometers in the formation of the Hellas impact basin during the period of heavy bombardment
. Anseris Mons is the type area
for a large set of rugged mountain blocks (>25 km across) that occur in a relatively continuous band 200 to 500 km wide around the western, northeastern, eastern, and southeastern rim of the Hellas basin. Many of the blocks, particularly along the western rim, are concentric with the basin and bounded by faults.
Rocks making up Anseris Mons and other massifs around Hellas are mapped as Noachian in age. However, work by Herbert Frey at NASA’s Goddard Spaceflight Center using Mars Orbital Laser Altimeter (MOLA) data indicates that the southern highlands of Mars contain numerous buried impact basins that are older than the visible Noachian-aged surfaces and which pre-date the Hellas impact. He suggests that the Hellas impact should mark the beginning of the Noachian period (base of the Noachian system). If Frey is correct, then Anseris Mons bedrock is actually pre-Noachian in age, perhaps dating back to over 4.1 billion years ago.
The Anseris Mons massif has undergone a significant amount of erosion since it was uplifted. The flanks of the mountain have huge triangular re-entrants
and associated spurs
, which give the massif a broad, pyramidal shape. The re-entrants were likely produced through a variety of mass-wasting
and periglacial
/glacial processes. A large cirque
-like re-entrant with channelized debris aprons or fans
is present on the south side of the mountain.
Massif
In geology, a massif is a section of a planet's crust that is demarcated by faults or flexures. In the movement of the crust, a massif tends to retain its internal structure while being displaced as a whole...
(mountain) in the southern highlands of Mars
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...
, located at the northeastern edge of Hellas Planitia
Hellas Planitia
Hellas Planitia, also known as the Hellas Impact Basin, is a huge, roughly circular impact basin located in the southern hemisphere of the planet Mars. It is the second or third largest impact crater and the largest visible impact crater known in the Solar System...
at longitude 86.6°E and latitude 29.81°S. The mountain is 58 km (36 mi) in diameter and rises to an elevation of approximately 4,200 m (13,780 ft) above datum (martian “sea” level) or about 6,200 m (20,300 ft) above the surrounding plains. The mountain lies in the southeastern quarter of the Iapygia quadrangle
Iapygia quadrangle
The Iapygia quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey Astrogeology Research Program. The Iapygia quadrangle is also referred to as MC-21 ....
(MC-21), straddling the boundary with the adjoining Hellas quadrangle
Hellas quadrangle
The Hellas quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey Astrogeology Research Program. The Hellas quadrangle is also referred to as MC-28 ....
(MC-28) to the south.
Anseris Mons is named from Anseris Fons, a telescopic albedo feature
Classical albedo features on Mars
The classical albedo features of Mars are the light and dark features that can be seen on the planet Mars through an Earth-based telescope. Before the age of space probes, several astronomers created maps of Mars on which they gave names to the features they could see. The most popular system of...
mapped by Greek astronomer E. M. Antoniadi in 1930. The name was approved by 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) in 1991.
Anseris Mons is not a volcano. Geologically, the massif is thought to be the eroded remnant of an ancient crustal block uplifted from depths of several kilometers in the formation of the Hellas impact basin during the period of heavy bombardment
Late Heavy Bombardment
The Late Heavy Bombardment is a period of time approximately 4.1 to 3.8 billion years ago during which a large number of impact craters are believed to have formed on the Moon, and by inference on Earth, Mercury, Venus, and Mars as well...
. Anseris Mons is the type area
Type locality (geology)
Type locality , also called type area or type locale, is the where a particular rock type, stratigraphic unit, fossil or mineral species is first identified....
for a large set of rugged mountain blocks (>25 km across) that occur in a relatively continuous band 200 to 500 km wide around the western, northeastern, eastern, and southeastern rim of the Hellas basin. Many of the blocks, particularly along the western rim, are concentric with the basin and bounded by faults.
Rocks making up Anseris Mons and other massifs around Hellas are mapped as Noachian in age. However, work by Herbert Frey at NASA’s Goddard Spaceflight Center using Mars Orbital Laser Altimeter (MOLA) data indicates that the southern highlands of Mars contain numerous buried impact basins that are older than the visible Noachian-aged surfaces and which pre-date the Hellas impact. He suggests that the Hellas impact should mark the beginning of the Noachian period (base of the Noachian system). If Frey is correct, then Anseris Mons bedrock is actually pre-Noachian in age, perhaps dating back to over 4.1 billion years ago.
The Anseris Mons massif has undergone a significant amount of erosion since it was uplifted. The flanks of the mountain have huge triangular re-entrants
Salients, re-entrants and pockets
A salient is a battlefield feature that projects into enemy territory. The salient is surrounded by the enemy on three sides, making the troops occupying the salient vulnerable. The enemy's line facing a salient is referred to as a re-entrant...
and associated spurs
Spur (mountain)
A spur is a subsidiary summit of a hill or mountain. By definition, spurs have low topographic prominence, as they are lower than their parent summit and are closely connected to them on the same ridgeline...
, which give the massif a broad, pyramidal shape. The re-entrants were likely produced through a variety of mass-wasting
Mass wasting
Mass wasting, also known as slope movement or mass movement, is the geomorphic process by which soil, regolith, and rock move downslope under the force of gravity. Types of mass wasting include creep, slides, flows, topples, and falls, each with its own characteristic features, and taking place...
and periglacial
Periglacial
Periglacial is an adjective originally referring to places in the edges of glacial areas, but it has later been widely used in geomorphology to describe any place where geomorphic processes related to freezing of water occur...
/glacial processes. A large cirque
Cirque
Cirque may refer to:* Cirque, a geological formation* Makhtesh, an erosional landform found in the Negev desert of Israel and Sinai of Egypt*Cirque , an album by Biosphere* Cirque Corporation, a company that makes touchpads...
-like re-entrant with channelized debris aprons or fans
Alluvial fan
An alluvial fan is a fan-shaped deposit formed where a fast flowing stream flattens, slows, and spreads typically at the exit of a canyon onto a flatter plain. A convergence of neighboring alluvial fans into a single apron of deposits against a slope is called a bajada, or compound alluvial...
is present on the south side of the mountain.