Brain terrain, also called knobs-brain coral and brain coral terrain, is a feature of the Martian surface, consisting of complex ridges found on lobate debris aprons, lineated valley fill and concentric crater fill. It is so named because it suggests the ridges on the surface of the human brain. Wide ridges are called closed-cell brain terrain, and the less common narrow ridges are called open-cell brain terrain. [1] It is thought that the wide closed-cell terrain contains a core of ice, and when the ice disappears the center of the wide ridge collapses to produce the narrow ridges of the open-cell brain terrain. Shadow measurements from HiRISE indicate the ridges are 4-5 meters high. [1] Brain terrain has been observed to form from what has been called an "Upper Plains Unit." The process begins with the formation of stress cracks. The upper plains unit fell from the sky as snow and as ice coated dust. [2]
Lobate debris aprons (LDAs) are geological features on Mars, first seen by the Viking Orbiters, consisting of piles of rock debris below cliffs. These features have a convex topography and a gentle slope from cliffs or escarpments, which suggest flow away from the steep source cliff. In addition, lobate debris aprons can show surface lineations as do rock glaciers on the Earth.
Lineated valley fill (LVF), also called lineated floor deposit, is a feature of the floors of some channels on Mars, exhibiting ridges and grooves that seem to flow around obstacles. Shadow measurements show that at least some of the ridges are several metres high. LVF is believed to be ice-rich. Hundreds of metres of ice probably lie protected in LVF under a thin layer of debris. The debris consists of wind-borne dust, material from alcove walls, and lag material remaining after ice sublimated from a rock-ice mixture. Some glaciers on Earth show similar ridges. High-resolution pictures taken with HiRISE reveal that some of the surfaces of lineated valley fill are covered with strange patterns called closed-cell and open-cell brain terrain. The terrain resembles a human brain. It is believed to be caused by cracks in the surface accumulating dust and other debris, together with ice sublimating from some of the surfaces. The cracks are the result stress from gravity and seasonal heating and cooling. This same type of surface is present on Lobate debris aprons and Concentric crater fill so all three are believed to be related.
A concentric crater fill is a landform where the floor of a crater is mostly covered with a large number of parallel ridges. It is common in the mid-latitudes of Mars, and is widely believed to be caused by glacial movement. Areas on Mars called Deuteronilus Mensae and Protonilus Mensae contain many examples of concentric crater fill.
Today it is widely accepted that glacier-like forms, lobate debris aprons, lineated valley fill, and concentric fill are all related in that they have the same surface texture. Glacier-like forms in valleys and cirque-like alcoves may coalesce with others to produce lobate debris aprons. When opposing lobate debris aprons converge, linear valley fill results. [3] They probably all contain ice-rich material.
Many of these features are found in the Northern hemisphere in parts of a boundary called the Martian dichotomy, mostly between 0 and 70 E longitudes. [4] Near this area are regions that are named from ancient places: Deuteronilus Mensae, Protonilus Mensae, and Nilosyrtis Mensae.
The most conspicuous feature of Mars is a sharp contrast, known as the Martian dichotomy, between the Southern hemisphere and the Northern. The two hemispheres' geography differ in elevation by 1 to 3 km. The average thickness of the Martian crust is 45 km, with 32 km in the northern lowlands region, and 58 km in the southern highlands.
Deuteronilus Mensae is a region on Mars 937 km across and centered at 43.9°N 337.4°W. It covers 344°–325° West and 40°–48° North. Deuteronilus region lies just to the north of Arabia Terra and is included in the Ismenius Lacus quadrangle. It is along the dichotomy boundary, that is between the old, heavily cratered southern highlands and the low plains of the northern hemisphere. The region contains flat-topped knobby terrain that may have been formed by glaciers at some time in the past. Deuteronilus Mensae is to the immediate west of Protonilus Mensae and Ismeniae Fossae. Glaciers persist in the region in modern times, with at least one glacier estimated to have formed as recently as 100,000 to 10,000 years ago. Recent evidence from the radar on the Mars Reconnaissance Orbiter has shown that parts of Deuteronilus Mensae do indeed contain ice.
Protonilus Mensae is an area of Mars in the Ismenius Lacus quadrangle. It is centered on the coordinates of 43.86° N and 49.4° E. Its western and eastern longitudes are 37° E and 59.7° E. North and south latitudes are 47.06° N and 39.87° N. Protonilus Mensae is between Deuteronilus Mensae and Nilosyrtis Mensae; all lie along the Martian dichotomy boundary. Its name was adapted by the IAU in 1973.
Lobate debris aprons, lineated valley fill, and concentric fill probably have dirt and rock debris covering huge deposits of ice. [5] [6] [7] [8]
Brain terrain, as seen by HiRISE under HiWish program Location is Ismenius Lacus quadrangle.
Lineated valley fill in Coloe Fossae, as seen by HiRISE. Scale bar is 500 meters long. Location is Ismenius Lacus quadrangle.
Closed-cell brain terrain, as seen by HiRISE under the HiWish program. This type of surface is common on lobate debris aprons, concentric crater fill, and lineated valley fill.
Context picture showing origin of next picture. The location is a region of lineated valley fill. Image from HiRISE under HiWish program.
Open and closed-cell brain terrain, as seen by HiRISE, under HiWish program.
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 and covers 0° to 60° east longitude and 30° to 65° north latitude. The quadrangle uses a Lambert conformal conic projection at a nominal scale of 1:5,000,000 (1:5M). The Ismenius Lacus quadrangle is also referred to as MC-5. The southern and northern borders of the Ismenius Lacus quadrangle are approximately 3,065 km (1,905 mi) and 1,500 km (930 mi) wide, respectively. The north-to-south distance is about 2,050 km (1,270 mi). The quadrangle covers an approximate area of 4.9 million square km, or a little over 3% of Mars’ surface area. The Ismenius Lacus quadrangle contains parts of Acidalia Planitia, Arabia Terra, Vastitas Borealis, and Terra Sabaea.
Coloe Fossae is a set of troughs in the Ismenius Lacus quadrangle of Mars. It is centered at 36.5 degrees north latitude and 302.9 west longitude. It is 576 km long and was named after a classical albedo feature.
Brain terrain being formed from a thicker layer, as seen by HiRISE under HiWish program. Arrows show the thicker unit breaking up into small cells.
Brain terrain is forming from the breakdown of upper plains unit, as seen by HiRISE under HiWish program Arrow points to a place where fractures are forming that will turn into brain terrain.
Brain terrain is forming from the breakdown of upper plains unit, as seen by HiRISE under HiWish program Arrow points to a place where fractures are forming that will turn into brain terrain.
Possible glacier surrounded by brain terrain, as seen by HiRISE under HiWish program
Wide view of brain terrain being formed, as seen by HiRISE under HiWish program
Brain terrain being formed, as seen by HiRISE under HiWish program Note: this is an enlargement of previous image using HiView.
Brain terrain being formed, as seen by HiRISE under HiWish program Note: this is an enlargement of a previous image using HiView.
Brain terrain being formed, as seen by HiRISE under HiWish program Note: this is an enlargement of a previous image using HiView. Arrows indicate spots where brain terrain is beginning to form.
Brain terrain being formed, as seen by HiRISE under HiWish program Note: this is an enlargement of a previous image using HiView. Arrows indicate spots where brain terrain is beginning to form.
Brain terrain being formed, as seen by HiRISE under HiWish program Note: this is an enlargement of a previous image using HiView.
Wide view of brain terrain being formed, as seen by HiRISE under HiWish program
Brain terrain being formed, as seen by HiRISE under HiWish program Note: this is an enlargement of the previous image using HiView.
Brain terrain being formed, as seen by HiRISE under HiWish program Note: this is an enlargement of a previous image using HiView.
Open and closed brain terrain with labels, as seen by HiRISE under HiWish program Image location is Ismenius Lacus quadrangle.
Open and closed brain terrain with labels, as seen by HiRISE under HiWish program Image location is Ismenius Lacus quadrangle.
Brain terrain being formed, as seen by HiRISE under HiWish program Image location is Ismenius Lacus quadrangle.
Brain terrain being formed, as seen by HiRISE under HiWish program Arrows point to locations where the brain terrain is starting to form. Image location is Ismenius Lacus quadrangle.
