Aram Chaos, centered at 2.6°N, 21.5°W, is a heavily eroded

impact crater An impact crater is a depression (geology), depression in the surface of a solid astronomical body formed by the hypervelocity impact event, impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal c ...

Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...

. It lies at the eastern end of the large canyon

Valles Marineris Valles Marineris (; Latin for ''Mariner program, Mariner Valleys'', named after the Mariner 9 Mars orbiter of 1971–72 which discovered it) is a system of canyons that runs along the Mars, Martian surface east of the Tharsis region. At more than ...

and close to Ares Vallis. Various geological processes have reduced it to a circular area of chaotic terrain. Aram Chaos takes its name from Aram, one of the classical albedo features observed by Giovanni Schiaparelli, who named it after the

Biblical The Bible is a collection of religious texts that are central to Christianity and Judaism, and esteemed in other Abrahamic religions such as Islam. The Bible is an anthology (a compilation of texts of a variety of forms) biblical languages ...

land of Aram. Spectroscopic observation from orbit indicates the presence of the mineral

hematite Hematite (), also spelled as haematite, is a common iron oxide compound with the formula, Fe2O3 and is widely found in rocks and soils. Hematite crystals belong to the rhombohedral lattice system which is designated the alpha polymorph of . ...

, likely a signature of a once aqueous environment.

Description

Aram Chaos is an impact crater on Mars measuring 280 kilometers (170 mi) in diameter. It lies in the Oxia Palus quadrangle in a region called Margaritifer Terra, and its exact coordinates on Mars are . The Thermal Emission Imaging System ( THEMIS) on the orbiter '' Mars Odyssey'' found gray crystalline hematite on the floor of Aram Chaos and CRISM, the spectroscope on the MRO, found hydrated sulfates, jarosite, and hematite. The floor of Aram Chaos also contains huge blocks of collapsed, or chaotic, terrain that formed when water or ice was catastrophically removed. Small, shallow outlet channels are also visible in the eastern wall of the impact crater, as well as a small outflow channel connecting Aram Chaos with the Ares Valles outflow channel.

Geology

Formation

Aram Chaos, as an

, started its formation with the high velocity impact of an unknown smaller body on the surface of Mars. This formed the large, circular depression that originally made up the crater. This crater was then filled with sediments, likely carried by

aeolian processes Aeolian processes, also spelled eolian, pertain to wind activity in the study of geology and weather and specifically to the wind's ability to shape the surface of the Earth (or other planets). Winds may erosion, erode, transport, and deposit ...

, that were deposited into Aram Chaos over time. Subsequently, and in tandem with the compilation of these sedimentary layers, and aquifer formed beneath the surface of the crater.

Chaotic Terrain and Aqueous Environment

Following the deposition of sedimentary layers and the formation of the subsurface aquifer, a catastrophic geologic event occurred which caused the release of the subsurface aquifer and the subsequent catastrophic flooding, creating chaotic terrain within Aram Chaos. The repetition of this process led to layered terrains within Aram Chaos, including layers of the mineral hematite. Several minerals in Aram Chaos, including the hematite sulfate minerals and water-altered silicates, suggest that a lake probably once existed within the crater at some point in time. Scientists also suggest that flood channels within Aram Chaos were carved within just weeks or months by catastrophic outflows of groundwater from beneath Aram Chaos and nearby regions. Because forming hematite requires liquid water, which cannot exist without a thick atmosphere, the presence of hematite also suggests that Mars had a much thicker atmosphere at some time in the past. Tilting and erosion of Aram Chaos is also evident in satellite imagery taken of the crater.

Possible Volcanic Constructs

There is a possible volcanic component to the formation of outflow channels in Aram Chaos. By melting the permafrost or ground ice originally in the crater, geothermal activity may have caused the creation of the visible outflow channels in the impact crater. High resolution MOC images of the chaotic terrains in Aram Chaos show possible volcanic features within the crater, including hills resembling volcanoes, possible magmatic intrusions within the older rock layers, and possible volcanic ash deposits on the crater floor.

Mineralogical Composition

Not including dust and regolith common on the surface of Mars, two distinct sections of identifiable minerals have been determined to exist within Aram Chaos: a mixture of hematite and/or goethite and a mixture of ferric oxides and sulfates. Specifically, these minerals can be seen as two layers in Aram Chaos, described from top to bottom. The first layer consists mostly of nanophase iron oxides, which is about 250-500 meters thick, while the second layer is made up of a less than 500 m layer of polyhydrated sulfate and hematite.

References

External links

* HiRISEbr>image of the area

The geology of Aram Chaos

More Images

File:Erosion in Aram Chaos.JPG, Erosion in Aram Chaos, as seen by THEMIS File:Badlands of Aram Chaos.jpg, Badlands of Aram Chaos File:Aram Chaos F669A03.jpg, Viking 1 Orbiter image File:Eastern Floor of Aram Chaos.jpg, Eastern floor of Aram Chaos File:Aram Chaos (2602867599).jpg, Minerals that form in water have been detected in the cliffs in the Aram Chaos region of Mars, as pictured. File:(PSP 002839 1825) Aram Chaos Sediments.jpg, Sediments in Aram Chaos File:(ESP 017528 1830) Gully Landforms in Aram Chaos.jpg, Gully landforms in Aram Choas File:Aram Chaos, perspective view ESA232259.tiff, Aram Chaos in perspective view File:Aram Chaos in false colour ESA217943.jpg, Aram Chaos in false color File:Aram Chaos, black and white ESA227913.jpg, Aram Chaos in black and white File:Aram Chaos (north to the right) ESA206460.tiff, Aram Chaos in true color File:PIA21195 - Aram Chaos - False Color.jpg, Aram Chaos as seen by HiRISE File:Just a Little Landslide.jpg, Hanging valleys in Aram Chaos, as seen by HiRISE under HiWish program File:Blocks in Aram.JPG, Blocks in Aram Chaos showing possible source of water, as seen by THEMIS File:Quadrângulo de Oxia Palus.JPG, Quadrangle map of Oxia Palus labeled with major features. Aram Chaos is near the bottom of the image. File:USGS-Mars-MC-11-OxiaPalusRegion-mola.png, Tography map of Oxia Palus region of Mars showing the location of a number of chaos regions, including Aram Chaos. File:Aram Chaos in the Oxia Palus quadrangle, Mars.jpg, Wide view of Aram Chaos, as seen by HiRISE under the HiWish program. The black strip is where data was not gathered. File:Light toned mound in Aram Chaos.jpg, Aram Chaos with a light toned mound as seen by HiRISE under the HiWish program. The mound probably contains water bearing minerals. File:Close view of light toned material in Aram Chaos.jpg, Light toned mound as seen by HiRISE under the HiWish program. The mound probably contains water bearing minerals. File:Dark sand on top of light toned material in Aram Chaos.jpg, Dark sand on top of light toned material, as seen by HiRISE under the HiWish program. {{Portal bar, Solar System Chaotic terrains on Mars # Margaritifer Sinus quadrangle