 Aram Chaos is the circular depression in the top left.Iani Chaos is in the bottom right. | |
| Location | Margaritifer Terra,Mars |
|---|---|
| Coordinates | 2°36′N21°30′W / 2.6°N 21.5°W /2.6; -21.5 |
| Diameter | 280 km (170 mi) |
| Depth | 3 km (1.9 mi) |
Aram Chaos, centered at 2.6°N, 21.5°W, is a heavily erodedimpact crater onMars. It lies at the eastern end of the large canyonValles Marineris and close toAres Vallis. Various geological processes have reduced it to a circular area ofchaotic terrain. Aram Chaos takes its name from Aram, one of theclassical albedo features observed byGiovanni Schiaparelli, who named it after theBiblical land ofAram.Spectroscopic observation from orbit indicates the presence of the mineralhematite, likely a signature of a once aqueous environment.
Aram Chaos is an impact crater on Mars measuring 280 kilometers (170 mi) in diameter. It lies in theOxia Palus quadrangle in a region calledMargaritifer Terra, and its exact coordinates on Mars are2°36′N21°30′W / 2.6°N 21.5°W /2.6; -21.5. The Thermal Emission Imaging System (THEMIS) on theorbiterMars Odyssey foundgray crystalline hematite on the floor of Aram Chaos andCRISM, the spectroscope on theMRO, 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 theAres Valles outflow channel.
Aram Chaos, as animpact crater, 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 This formed the large, circular depression that originally made up the crater.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 byaeolian processes, 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.
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.[1][2][3] 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.[4][5] 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.[6] 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.
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.[7] 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.
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 ofhematite and/orgoethite and a mixture offerric oxides andsulfates.[8] 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.[9][10]
Ferric hydroxysulfate (Fe3+SO4OH) has been found in Aram Chaos. It was probably formed from the heating and oxidation of hydrated ferrous sulfates. The heat may have come from the deposition of lava or ash. Another psossibility is that heat came from the ground by way of hydrothermal processes. This iron and sulfur compound was discovered with the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) instrument.[11][12]
.jpg)
_Aram_Chaos_Sediments.jpg)
_Gully_Landforms_in_Aram_Chaos.jpg)
