Topographical Map for the Casius Region
The southern and northern borders of the Casius Region are approximately 3,065 km and 1,500 km wide, respectively. The north to south distance is about 2,050 km. (slightly less than the length of Greenland.
Image of Casius Region
The high latitude Casius Region bears several features that are believed to indicate the presence of ground ice. Patterned ground is one such feature. Usually, polygonal shapes are found pole ward of 55 degrees latitude. Other features associated with ground ice are Scalloped Topography, Ring Mold Craters, and Concentric Crater Fill.
Ring Mold Craters
Ring Mold Craters look like the ring molds used in baking. They are believed to be caused by 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." They may be an easy way for future colonists of Mars to find water ice.
The Nilosyrtis Mensae Channel
Nilosyrtis Mensae like several other features, sits in more than one Region. Part of Nilosyrtis Mensae is in the Ismenius Lacus Region, the rest is in Casius Region. So leaving the Protonilus Mensae we enter the Nilosyrtis Mensae just east of the border of the Casius Region then leaving the Ismenius Lacus Region in the Nilosyrtis Mensae we enter the Casius Region while following the shoreline of the Dichotomy on Mars. It is centered on the coordinates of 36.87° N and 67.9° E. Its western and eastern longitudes are 51.1° E and 74.4° E. North and south latitudes are 36.87° N and 29.61° N. Its name was adapted by the IAU in 1973. It was named after a classical albedo feature, and it is 705 km (438 mi) across.
Ridges in surface of Nilosyrtis Mensae
The surface of Nilosyrtis Mensae is classified as fretted terrain. This terrain contains cliffs, mesas, and wide flat valleys. Surface features are believed to have been caused by debris-covered glaciers.
South of this area in the southwest corner of the Casius Region is the last part of Terra Sabaea that we see. Going from from south to north at about 30-33 Degrees North, Huo Hsing Vallis empties into the Nilosyrtis Mensae.
Huo Hsing Vallis
Huo Hsing Vallis is an ancient river valley that originates south in the Uplands of the Syrtis Major Region of Mars at 30.5° North latitude and 293.4° West longitude. It is about 318 km long and was named after the word for "Mars" in Chinese. It goes through the Terra Sabaea in the Casius Region and emptied into the Nilosyrtis Mensae.
North of the Nilosyrtis Mensae located near the western border of the Casius region at about 42° North is Renaudot Crater.
Dunes and Bedrock in Renaudot Crater
Concentric Crater Fill: Concentric crater fill is when the floor of a crater is mostly covered with a large number of parallel ridges. They are thought to result from a glacial type of movement. Sometimes boulders are found on concentric crater fill; it is believed they fall off the crater wall, then were transported away from the wall with the movement of the glacier.
Going north from Renaudot Crater to about 50°N. 35°E we come to the Pyramus Fossae.
Possible Duricrust in Pyramus Fossae
Duricrust is a hard layer on or near the surface of soil. Duricrusts can range in thickness from a few millimeters or centimeters to several meters. It is typically formed by the accumulation of soluble minerals deposited by mineral-bearing waters that move upward, downward, or laterally by capillary action, commonly assisted in arid settings by evaporation. Minerals often found in duricrust include silica, iron, calcium, and gypsum. Duricrust is often studied during missions to Mars because it may help prove the planet once had more water. Duricrust was found on Mars at the Viking 2 landing site, and a similar structure, nicknamed "Snow Queen," was found under the Phoenix landing site. Phoenix's duricrust was later confirmed to be water-based.
Going east from there we come to Utopia Planitia. The Utopia Planitia (Latin: "Nowhere Plain") is the largest recognized impact basin on Mars and in the solar system with an estimated diameter of 3300 km, is the Martian area where the Viking 2 lander touched down and began exploring on September 3, 1976 in the Cebrenia Region. The Utopia region is located in both the Casius Region and the Cebrenia Region of Mars to the east. Many rocks in Utopia Planitia appear perched, as if wind removed much of the soil at their bases. A hard surface crust is formed by solutions of minerals moving up through soil and evaporating at the surface. Some areas of the surface exhibit what is called "scalloped topography," a surface that seems to have been carved out by an ice cream scoop. This surface is thought to have formed by the degradation of an ice-rich permafrost.
Utopia Planitia Area
Utopia Rupes is south of Utopia Planitia in the central are of the Region at about 40-44°N.
Polygons and Pits in Utopia Rupes
South of Utopia Rupes we come to the Astapus Colles:
Astapus Colles mounds and knobs, as seen by HiRISE. Scale bar is 500 meters long.
Astapus Colles : is a group of hills in the Casius Region of Mars, located at 35.5 North and 272.3 West. It is 580 km across named after an albedo feature.
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 based on albedo features. The most popular system of nomenclature was devised by Giovanni Schiaparelli, who used names from classical antiquity. Today, the improved understanding of Mars enabled by space probes has rendered many of the classical names obsolete for the purposes of cartography; however, some of the old names are still used to describe geographical features on the planet.
East of Astapus Colles is Adamas Labyrinthus located at about 35°N.
In the Adamas Labyrinthus area we come to abrupt landscape changes.
A review of existing images of Mars reveals a diverse landscape. In some instances, such as around volcanoes and in valleys, a casual glance suggests the features are much like those here on Earth. Closer inspection, however, often confirms differences in scale and or subtle characteristics relative to their more familiar terrestrial counterparts. These same images also reveal a Mars that is often very different form the Earth. Some locations are marked by huge jumbles of blocks forming chaotic terrain, whereas others are buried beneath blankets of dust.
Just North of Adamas Labyrinthus is Nier Crater.
Gullies in the walls of Nier Crater
To the north east on the Region border is Vivero Crater. Located at about 49°North.
The Central Peak in Vivero Crater
The high-velocity collision of interplanetary objects (mostly asteroids, also comets) with the surface of Mars creates primary impact craters. The primary impacts may eject significant numbers of rocks at high velocity which fall back to make secondary craters. The study of craters is important for many reasons, such as understanding cratering mechanics, attempts to estimate the ages of terrains or processes, understanding properties of the target material such as presence of ground ice, and understanding landscape evolution (since we have some understanding of the morphology of pristine craters). The study of small craters (< 10 m diameter) can provide information about atmospheric density, and perhaps how it has varied over time. Not all craters are of impact origin—craters can also form from volcanism or ground collapse.
Next we come to Bacolor Crater right in the southeast corner of the Casius Region.
Bacolor Crater Ejecta, as seen by HiRISE. Scale bar is 1000 meters long.
Bacolor Crater: is a crater located at 33 North and 241.4 West. It is 20.8 km in diameter and was named after a town in the Philippines.