Margaritifer Terra

Margaritifer Terra (/ˌmɑːrɡəˈrɪtəfər ˈtɛrə/) is an ancient, heavily cratered region of Mars. It is centered just south of the Martian equator at 4°54′S 25°00′W / 4.9°S 25°W / -4.9; -25 and covers 2600 km at its widest extent.^[1] The area reveals "chaos terrain", outflow channels, and alluvial plains that are indicative of massive flooding. Wind erosion patterns are also in evidence. A region within the terra shows some of the highest valley network densities on the planet. Ares Vallis is another notable feature, where the flood and flow patterns are in evidence; it was the landing site of the Soviet Mars 6 lander^[2] and NASA's Mars Pathfinder.^[3] It was also one of several proposed landing sites for the Mars 2020 Rover.^[4]

Holden and Eberswalde, craters in Margaritifer Terra, are thought to have formerly held lakes because they contain deltas and iron/magnesium smectite minerals which need water to form.^[5] The Uzboi-Landon-Morava (ULM) system of paths for water flow is found in Margaritifer Terra. Researchers think that great flood channels in this region were carved quickly in just weeks or months by catastrophic outflows of groundwater.^[6] 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.^[7]

Margaritifer Terra was named in 1979, after the Pearl Coast, south India. Part of it is found in the Margaritifer Sinus quadrangle and part in the Oxia Palus quadrangle.