Casius quadrangle

MC-06

Casius

30–65° N

60–120° E

Quadrangles

Atlas

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  Casius quadrangle elevations

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                              Scenes of the Casius quadrangle

The Casius quadrangle shows many features that indicate a water-rich past and much ice currently frozen in the ground. Features that are evidence of ice in the ground are pedestal craters, channels, glaciers, concentric crater fill, ring-mold craters, scalloped terrain, and polygonal ground. This region also has some landscapes that are mysteries--like strange, but beautiful linear ridge networks.

In this article, some of the best pictures from a number of spacecraft will show what the landscape looks like in this region. The origins and significance of all features will be explained as they are currently understood.

The Casius quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS). The quadrangle is located in the northern hemisphere and covers 30° to 65° north latitude and 240° to 300° west longitude (120° to 60° east longitude). It is also described as MC-6 (Mars Chart-6). Casius quadrangle contains part of Utopia Planitia and a small part of Terra Sabaea.

Origin of name

Casius is the name of a classical albedo features on Mars that is centered at 40° N and 100° E. The feature was named by Giovanni Schiaparelli in 1888 after Ras Kouroun (Mt Casius) in Egypt, famous in antiquity for the nearby Lake Bardawil coastal marshes in which whole armies were reputed to have drowned. The name was approved by the International Astronomical Union (IAU) in 1958. All names for astronomy features must eventually be approved by IAU.

Polygonal patterned ground

       Color view of polygonal ground, as seen by HiRISE under HiWish program

Polygonal, patterned ground is quite common in some regions of Mars, especially in scalloped topography or scalloped terrain. Patterned ground is widespread on the Earth in cold climates where the ground is frozen. Under Martian conditions, it is at least partially caused by the sublimation of ice from the ground. Sublimation is the direct change of solid ice to a gas. This is similar to what happens to dry ice on the Earth. Places on Mars that display polygonal ground may indicate where future colonists can find water ice. Patterned ground forms in a mantle layer that fell from the sky when the climate was different. Polygonal ground is sometimes divided into two kinds: high center and low center. The middle of a high center polygon is 10 meters across and its troughs are 2–3 meters wide. Low center polygons are 5–10 meters across and the boundary ridges are 3–4 meters wide. Low center polygons have been proposed as a marker for ground ice.

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  Patterned ground in the form of polygonal features is associated with ground ice. It is rare to be found this far south (45 degrees north latitude). Picture taken by Mars Global Surveyor.

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  Close, color view of patterned ground

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  Close, color view of polygonal ground

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  Large and small polygonal ground Area with small, low-center polygons is labeled.

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  High and low center polygons

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  Low-centered polygons in a region of scalloped terrain

                         Scalloped terrain labeled with both low center polygons and high center polygons

Ring mold craters

Ring mold craters look like the ring molds used in baking. A popular idea for their formation is an impact into ice. The ice is covered by a layer of debris. They are found in parts of Mars that have buried ice. Laboratory experiments confirm that impacts into ice result in a "ring mold shape." Ring mold craters may show future colonists of Mars where to find water ice.

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  Possible ring mold crater, as seen by HiRISE under the HiWish program. Crater shape is due to impact into ice.

Ring-mold craters form when an impact goes through to an ice layer. The rebound forms the ring-mold shape, and then dust and debris settle on the top to insulate the ice.

Concentric crater fill

Concentric crater fill is when the floor of a crater is mostly covered with a large number of concentric ridges. These ridges are thought to result from a glacial type of movement. Sometimes boulders are found on concentric crater fill; it is believed they fell off crater wall, and then were transported away from the wall with the movement of the glacier. In certain places on the earth large boulders are found that are different than the rocks in the area. Studies have shown that they often have been transported many miles inside or on top of glaciers. They are called erratics. Because ice moves boulders on the Earth, researchers believe that boulders on concentric crater fill originated from crater walls and then were moved by ice movement in the crater. There is strong evidence of ice in craters. Based on accurate topography measures of height at different points in these craters and calculations of how deep the craters should be based on their diameters, it is thought that the craters are 80% filled. That is, they hold hundreds of meters of material that probably consists of ice with a few tens of meters of surface debris. The ice accumulated in the crater from snowfall in previous climates.

High resolution pictures taken with HiRISE reveal that some of the surfaces of concentric crater 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.

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  Crater with concentric crater fill, as seen by CTX (on Mars Reconnaissance Orbiter).

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  Well-developed hollows Note: this is an enlargement of the previous CTX image.

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  Close-up that shows cracks containing pits on the floor of a crater containing concentric crater fill, as seen by HiRISE under HiWish program.

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  Close-up that shows cracks containing pits on the floor of a crater Cracks may start as a line of pits that enlarge, and then join.

                   Crater floor showing concentric crater fill, as seen by HiRISE under HiWish program

Glaciers

Old glaciers are found in many places on Mars. Some are associated with gullies.

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  Glacier on a crater floor, as seen by HiRISE under HiWish program The cracks in the glacier may be crevasses. There is also a gully system on the crater wall.

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  Valley showing Lineated valley fill Linear valley flow is caused by ice movements; so it is a type of glacial flow.

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  Flow (Glacier)

Nilosyrtis

Nilosyrtis runs from about 280 to 304 degrees west longitude, so like several other features, it lies in more than one quadrangle. Part of Nilosyrtis is in the Ismenius Lacus quadrangle, the rest is in Casius quadrangle.

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  Channel in Nilosyrtis that was formed when a lake in a 45-mile-wide crater drained, as seen by THEMIS.

      Nilosyrtis, as seen by HiRISE.

Climate change caused ice-rich features

Many features on Mars, including many in Casius quadrangle, are believed to contain large amounts of ice. The most popular model for the origin of the ice is climate change from large changes in the tilt of the planet's rotational axis. At times the tilt has even been greater than 80 degrees Large changes in the tilt explains many ice-rich features on Mars.

Studies have shown that when the tilt of Mars reaches 45 degrees from its current 25 degrees, ice is no longer stable at the poles. Furthermore, at this high tilt, stores of solid carbon dioxide (dry ice) sublimate, thereby increasing the atmospheric pressure. This increased pressure allows more dust to be held in the atmosphere. Moisture in the atmosphere will fall as snow or as ice frozen onto dust grains. Calculations suggest this material will concentrate in the mid-latitudes. Scientists have gathered data on the weather on Mars for many decades. Using the vast amounts of information, scientists have developed detailed models about the Martian climate. They call these models or theories, general circulation models. General circulation models of the Martian atmosphere predict accumulations of ice-rich dust in the same areas where ice-rich features are found. When the tilt begins to return to lower values, the ice sublimates (turns directly to a gas) and leaves behind a lag of dust. The lag deposit caps and thereby insulates the underlying material so with each cycle of high tilt levels, some ice-rich mantle remains behind. Note, that the smooth surface mantle layer probably represents only relative recent material.

Mars Science Laboratory

Nilosyrtis contains things of great interest to researchers as such it is one of the places that was proposed as a landing site for the Mars Science Laboratory (Curiosity). However, it did not make the final cut. It was in the top 7, but not in the top 4. The aim of the Mars Science Laboratory is to search for signs of ancient life. It is hoped that a later mission could then return samples from sites identified as probably containing remains of life. To safely bring the craft down, a 12-mile-wide, smooth, flat circle is needed. Geologists hope to examine places where water once ponded. They would like to examine sediment layers. They did find these layers in Gale Crater where the rover successfully landed.

Layers

Many places on Mars show rocks arranged in layers. A detailed discussion of layering with many Martian examples can be found in Sedimentary Geology of Mars. Rock can form layers in a variety of ways. Volcanoes, wind, or water can produce layers. Layers may be formed by groundwater rising up depositing minerals and cementing sediments. The hardened layers are consequently more protected from erosion. This process may occur instead of layers forming under lakes.

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  Layers, as seen by HiRISE under HiWish program.

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  Layers in Monument Valley. These are accepted as being formed, at least in part, with the aid of water. Since Mars contains similar layers, water remains as a major cause of layering on Mars.

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  Wide view of layers

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  Close view of layers

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  Close view of layers, as seen by HiRISE under HiWish program A ridge cuts across the layers at a right angle.

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  Close view of layers, as seen by HiRISE under HiWish program

                      Close view of layers Colored part is about 1 km across.

Gullies

Martian gullies are small, incised networks of narrow channels and their associated downslope deposits. They are named for their resemblance to terrestrial gullies. First discovered in images from Mars Global Surveyor, they occur on steep slopes, especially on the walls of craters. Usually, each gully has an alcove at its head, a fan-shaped apron at its base, and a single thread of incised channel linking the two, giving the whole gully an hourglass shape. They are believed to be relatively young because they have few, if any craters. On the basis of their form, aspects, positions, and location amongst and apparent interaction with features thought to be rich in water-ice, many researchers believed that the processes carving the gullies involve liquid water. However, with more observations and research this idea has changed. Scientists always want observations to fit the hypothesis or theory. As soon as gullies were discovered, researchers began to image many gullies over and over, looking for possible changes. By 2006, some changes were found. Later, with further analysis it was determined that the changes could have occurred by dry granular flows rather than being driven by flowing water. With continued observations many more changes were found in Gasa Crater and others. With more repeated observations, more and more changes were found; since the changes occur in the winter and spring, experts are tending to believe that gullies were formed from dry ice. Before-and-after images demonstrated the timing of this activity coincided with seasonal carbon-dioxide frost and at temperatures that would not have allowed for liquid water. When dry ice frost changes to a gas, it may lubricate dry material to flow especially on steep slopes. In some years frost build up may be-as thick as 1 meter.

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  Gullies in crater, as seen by HiRISE under HiWish program

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  Close view of gully in crater, as seen by HiRISE

Pedestal craters

A pedestal crater is an impact crater with its ejecta sitting above the surrounding terrain and thereby forming a raised platform (like a pedestal). They form when an impact crater ejects material which forms an erosion-resistant layer, thus causing the immediate area to erode more slowly than the rest of the region. Some pedestals have been accurately measured to be hundreds of meters above the surrounding area. This means that hundreds of meters of material were eroded away--and much of the eroded substance was probably water ice. The result is that both the crater and its ejecta blanket stand above the surroundings. Pedestal craters were first observed during the Mariner missions

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  Pedestal crater The ejecta is not symmetrical around crater because the asteroid came at a low angle out of the North East. The ejecta protected the underlying material from erosion; hence the crater looks elevated.

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  Pedestal crater Dark lines are dust devil tracks.

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  Pedestal crater Scallops are forming at the bottom edge of the pedestal.

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  Pedestal crater with boulders along rim. Such craters are called "halo craters." Picture taken with HiRISE under HiWish program.

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  Pedestal craters form when the ejecta from impacts protect the underlying material from erosion. As a result of this process, craters appear perched above their surroundings

Cones

Some locations on Mars display a large number of cones. Many have pits at the top. There have been a several ideas put forth as to their origins. Many may be mud volcanoes. Others may be from hot lava flowing over ice-rich ground. Some are in the Casius quadrangle like the ones below.

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  Cones along with a band of material of unknown origin.

  Close view of cones along with a band of material of unknown origin.  Arrows point to the edge of bands.

Linear ridge networks

           Close view of network of ridges,  as seen by HiRISE   Box shows the size of a football field.

Linear ridge networks are found in various places on Mars in and around craters. Ridges often appear as mostly straight segments that intersect in a lattice-like manner. They are hundreds of meters long, tens of meters high, and several meters wide. One popular idea for origin is that impacts created fractures in the surface, these fractures later acted as channels for fluids. Fluids turned into hard, narrow walls. With the passage of time, surrounding material was eroded away, thereby leaving hard ridges behind. Since the ridges occur in locations with clay, these formations could serve as a marker for water because clay requires water for its formation.

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  Network of ridges Ridges may be formed in various ways.

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  Color, close-up of ridges seen in previous image, as seen by HiRISE under HiWish program

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  Close-up and color image of linear ridge network

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  More linear ridge networks

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  Close view of network of ridges

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  Close view of network of ridges

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  Wide view of ridge network Image is about 1 km across.

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  Close view of ridge network, as seen by HiRISE under HiWish program Image is about 1 km across.

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  Close view of ridge network, as seen by HiRISE under HiWish program Image is about 1 km across.

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  Close view of ridge network Image is about 1 km across.

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  Close, color view of ridges

                             Wide view of ridge networks

Scalloped terrain

                            Scalloped ground, as seen by HiRISE under HiWish program 

Scalloped depressions are believed to form from the removal of subsurface material, possibly interstitial ice, by sublimation (direct transition of a material from the solid to the gas phase with no intermediate liquid stage). This process may still be happening at present. This topography may be of great importance for future colonization of Mars because it may point to deposits of pure ice. The notion that this type of terrain could tell us where to find stores of water for future colonies received a big boost from research in 2016.

On November 22, 2016, NASA reported finding a large amount of underground ice in the Utopia Planitia region which contains a great deal of scalloped terrain. The volume of water detected has been estimated to be equivalent to the volume of water in Lake Superior. The volume of water ice in the region were based on measurements from the ground-penetrating radar instrument on Mars Reconnaissance Orbiter, called SHARAD. From the data obtained from SHARAD, “dielectric permittivity”, or the dielectric constant was determined. The dielectric constant value was consistent with a large concentration of water ice.

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  Scalloped terrain, as seen by HiRISE under HiWish program

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  Close-up of scalloped ground Surface is divided into polygons; these forms are common where ground freezes and thaws. Note: this is an enlargement of a previous image.

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  Scalloped terrain, as seen by HiRISE under HiWish program

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  Scalloped terrain

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  Scalloped terrain and polygonal ground

Layers in craters

Layers along slopes, especially along crater walls are believed to be the remains of a once widespread material that has mostly been eroded away.

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  Layers in craters, as seen by HiRISE under the HiWish program. Area was probably covered over by these layers; the layers have now eroded away except for the protected interior of craters.

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  Layers in craters

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  Layered features in craters, as seen by HiRISE under HiWish program

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  Close view of layered feature in crater Feature seems to be higher than parts of the crater rim.

Dipping layers

Dipping layers are common in some regions of Mars. They may be the remains of mantle layers. Mantle, often called latitude dependent mantle, falls from the sky during certain climate periods. It is ice-rich and often makes a different layer each season that it comes out of the sky. When the climate changes it may disappear from most of land, but it may remain in protected spots.

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  Dipping layers and layers of mantle, as seen by HiRISE under HiWish program The dipping layers look similar to layers of mantle.

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  Close view of mantle near a layered feature

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  Close view of mantle near the dipping layers, as seen by HiRISE under HiWish program

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  Mantle layers that may be the start of a set of dipping layers.

Craters

Impact craters generally have a rim with ejecta around them, in contrast volcanic craters usually do not have a rim or ejecta deposits. If one measures the diameter of a crater, the original depth can be estimated with various ratios. Because of this relationship, researchers have found that many Martian craters contain a great deal of extra material that was deposited after the impact. Much of it is believed to be ice deposited when the climate was different. Sometimes craters expose layers that were buried. Rocks from deep underground are tossed onto the surface. Hence, craters can show us what lies deep under the surface.

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  Crater in the Adamas Labyrinthus Region, as seen by HiRISE.

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  Bacolor Crater Ejecta, as seen by HiRISE. Scale bar is 1000 meters long.

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  Renaudot Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter).

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  Dunes and old glaciers in Renaudot Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter). Arrows point to old glaciers along the crater wall. Dark dots are dunes. Note: this is an enlargement of the previous image.

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  Ring of boulders around rim of old crater with dust devil tracks in the background, as seen by HiRISE under HiWish program

Dust devil tracks

Many areas on Mars experience the passage of giant dust devils. These dust devils leave tracks on the surface of Mars because they disturb a thin coating of fine bright dust that covers most of the Martian surface. When a dust devil goes by, it blows away the coating and exposes the underlying dark surface. Within a few weeks, the dark track assumes its former bright color, either by being re-covered through wind action or due to surface oxidation through exposure to sunlight and air.

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  Dust devil tracks

                                     Pedestal crater and dust devil tracks

Pitted surface

                          Close view of lines of pits,  as seen by HiRISE under HiWish program

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  Wide view of a surface with lines of pits

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  Close, color view of lines of pits

Other views from Casius

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  Astapus Colles Mounds and Knobs, as seen by HiRISE. Scale bar is 500 meters long.

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  Holes and hollows on crater floor, as seen by HiRISE under HiWIsh program.

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  Ribbed terrain The low places forms as ice leaves the ground.

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  Ice layers in crater, as seen by HiRISE under HiWish program

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  Close, color view of ice layers in a crater Both, open and closed brain terrain are visible.

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  Dunes, as seen by HiRISE under HiWish program

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  Close view of boulders on lower left of crater rim Box is the size of a football field, so boulders are roughly the size of cars or small houses. Picture taken with HiRISE under HiWish program.

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  Close view of boulders along crater rim Boulders are roughly the size of cars or small houses.

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  Wide view of fractured surface and pits along wall of crater

                                        Close view of cracks and boulders

See also

• Dark slope streaks
• Geography of Mars
• High Resolution Imaging Science Experiment (HiRISE)
• HiWish program
• How are features on Mars Named?
• Glaciers on Mars
• Layers on Mars
• Mars Global Surveyor
• Martian features that are signs of water ice
• Martian gullies
• Oceans on Mars
• Periodic climate changes on Mars
• Rivers on Mars
• Sublimation landscapes on Mars

External links

• Martian Ice - Jim Secosky - 16th Annual International Mars Society Convention
• https://www.youtube.com/watch?v=kpnTh3qlObk[T. Gordon Wasilewski - Water on Mars - 20th Annual International Mars Society Convention] Describes how to get water from ice in the ground

• Changes in dust devil tracks