Post contributed by Solmaz Adeli, Deutsches Zentrum für Luft- und Raumfahrt (DLR), Institute of Planetary Research, Berlin, Germany
Image 1: Kārūn Valles located on the rim of the Ariadnes Colles basin. The visible channel head and deep grooves are shown (detail of CTX image D10_031182_1435). (b) The Kārūn Valles alluvial fan. Note the elongated depositional bars and their wide distribution. (c) A zoom on one of the braided bars. The flow direction is indicated by dashed arrows (detail of HiRISE image ESP_043261_1440).
The Amazonian period on Mars, meaning roughly the last 3 Ga, is globally believed to have been cold and hyperarid [e.g., Marchant and Head, 2007]. Recent geomorphological observations, however, have revealed the presence of well-preserved Amazonian-aged fluvial valleys in both the north and south mid-latitude regions of Mars [Howard and Moore, 2011; Hobley et al., 2014; Salese et al., 2016; Wilson et al., 2016]. These features point to one or several climate change phase(s) during Amazonian which could have sustained liquid water at the martian surface. These climate changes could have been triggered by obliquity oscillations [Laskar et al., 2004] causing the transportation of ice from polar regions and its re-deposition at lower latitudes. Episodic melting events during Amazonian, subsequently, formed valleys and other fluvial features, in the mid-latitude regions.
![Image 1: View of Morella Crater and the complex of Elaver Vallis channels eroded by floodwaters released when the crater rim was breached. The distal reaches of Elaver Vallis were obliterated by the southward expansion of Ganges Chasma, which is 5 km deep. The chasma as seen today did not exist during the Elaver flood, otherwise high groundwater pressures would have been relieved by breakouts in the walls and floor of the chasma [graphic is a mosaic of THEMIS daytime infrared (IR) images].](https://planetarygeomorphology.files.wordpress.com/2014/03/image-1.jpg?w=600&h=328)
