Aram Chaos, centered at 2.6°N, 21.5°W, is a heavily erodedimpact crater on the planetMars. It lies at the eastern end of the large canyon Valles Marineris 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 land of Aram. Spectroscopicobservation from orbit indicates the presence of the mineralhematite, likely a signature of a once aqueous environment. Aram Chaos measures about across, and lies in a region called Margaritifer Terra, where many water-carved channels show that floods poured out of the highlands onto the northern lowlands ages ago. It is in the Oxia Palus quadrangle. The Thermal Emission Imaging System on the orbiterMars Odyssey found gray crystalline hematite on the floor of Aram. CRISM, the spectroscope on the MRO, found hydrated sulfates, jarosite, and hematite. Hematite is an iron-oxide mineral that can precipitate when ground water circulates through iron-rich rocks, whether at normal temperatures or in hot springs. The floor of Aram contains huge blocks of collapsed, or chaotic, terrain that formed when water or ice was catastrophically removed. Elsewhere on Mars, the release of groundwater produced massive floods that eroded the large channels seen in Ares Vallis and similar outflow valleys. In Aram Chaos, however, the released water stayed mostly within the crater's ramparts, eroding only a small, shallowoutlet channel in the eastern wall. Several minerals including hematite sulfate minerals, and water-altered silicates in Aram suggests that a lake probably once existed within the crater. Scientists suggest that enormous flood channels were carved quickly in just weeks or months by catastrophic outflows of groundwater from beneath Aram Chaos and nearby regions. Because forming hematite requires liquid water, which could not long exist without a thick atmosphere, Mars must have had a much thicker atmosphere at some time in the past.
