Arabia Geology

Geology of Arabia This article will cover the geology in and around the Arabia region of Mars. The map to the right shows elevations with white being the highest and dark blue the lowest. Arabia is just to the west of a classic dark feature, called Syrtis Major. It's elevation as shown on the colored elevation map is rather low. The surface of Arabia is heavily cratered, like almost all terrain in the south. However, the southern hemisphere is known as the "Highlands," due to its high elevations. The reason Arabia is rather low, but heavily createred remains a mystery. Some scientists believe that early on a large asteroid struck the region and knocked out an enormous amount of material. Picture credit: MOLA Science Team/GSFC/NASA
With this black and white image produced by Malin Space Sciences Systems/NASA using Mars Global surveyor (MGS) images from the Mars Orbital Camera (MOC), the entire Arabia region lies together in the middle of the image. In this image, as in many other displays of Mars, zero longitude is in the center. The dark spot, just to the east of Arabia is called Syrtis Major and is a volcanic feature. Nili Patera, a volcano in that area has been found to contain highly evolved rocks, like granite, andesite, and dacite. That means that they contain much more of the mineral quartz than most of the dark basalt that covers nearly all of Mars.

	The northern Arabia region contains some of the most unusual and mysterous areas on Mars, called "fretted terrain"--not because it is worried, but because it is greatly eroded. When people worry, they may have a wrinkled forehead. Erosion of fretted terrain has formed many elongated features like the wrinkles on an anxious person's brow. This large area is in the Ismenius Lacus Quadrangle. This region of greatly eroded material is found between two major zones on Mars--low elevation, uncreatered plains of the northern hemisphere and high elevations, heavily crated areas that cover the southern hemisphere and part of the northern hemisphere. The picture at the left shows buttes and giant mesas with cliff-like sides.
	Because linear features (ridges and grooves) commonly occur on the valley floors, many researchers believe a flow of ice is involved. These types of features are similar to what is found on Alpine Glaciers on Earth.

Of special interest to Mars researchers are places showing many rock layers. The layers show some sort of changes in the past. They may have been made by the wind, by volcanoes, or possibly by water. On Earth, such layers often are formed under lakes. Many parts of Arabia display layers.
Becquerel crater lies in the western part of Arabia. It is one of many craters the west that show many layers.
Several public target images found locations in the middle of Arabia that contain layers. Layers were found in pubic target images S21-00037, S07-00496, and R19-01445. These layers were similar to ones previously observed in Henry crater.
The image to the right shows enlarged parts of a group of buttes that formed in a large crater. The picture at the far right contains a rectangle that shows where the locations of the close-ups. This large crater was probably filled with sediments that later eroded. The buttes are all that is left of layers that filled the entire crater. This landscape is similiar to many areas in western USA such as Momument Valley. The material on the floor is greatly eroded. Henry crater below contains a large deposit (a mound) that has not eroded to the extent of this crater.

The picture to the right shows some layers that are not found within a large crater.
	Four locations in the Arabia area show many layers. The layers may be formed by various processes including volcanos, wind, or water. These four locations lie far from each other. The processes that put the layers down could have been widespread. Perhaps, the whole area was covered with a vast sea! Next, we will examine the elevations of some of these places. The zero point of elevation on Mars is called the datum. It is the elevation at which the atmospheric pressure is 6.1 millibars. Mars has no ocean; hence "sea level" can't be used. In contrast the pressure on Earthat sea level is close to 1000 millibars! Elevations can be determined by using NASA's marsoweb tool found at marsoweb.nas.nasa.gov

	We can see from the profiles that the elevations are much different for three locations. The lowest points of the profiles generally correspond to the lowest layers. Tikhonravov is the highest at 1600 meters below Mars baseline. Henry is next with an elevation of 2000 meters below baseline. Public target R19-01445 is the deepest with an elevation of 2500 metrs below baseline. The presence of layers at different depths or elevations is consistent with certain areas undergoing uplift. For a much more detailed treatment of Arabia see "Possible ancient giant basin and related water enrichment in the Arabia Terra province, Mars" by Dohm, J et al. in Icarus 2007: 190:pp. 74-92. Return to homepage