Age-Dating Drainage Basins in Sabae and Arabia Terrae, Mars

The precise timing of drainage basins is critical to understanding the climate history on Mars. One of the obvious problems with age-dating valley networks is the fact that they are small, linear features that are easily destroyed by large impact craters, thus counting craters on valley networks themselves is difficult at best. We proposed a new global study dating 27 drainage basins and subbasins in Sabaea and Arabia Terrae with the basin age-dating technique. Valley networks are contained within drainage basins, which is defined as the area that contributes water to a particular channel or set of channels . For our study, we used THEMIS (Thermal Emission Imaging System) visible images with a spatial resolution of 100 m/pixel which allow us to count craters with diameter of 1 km and larger. A digital elevation model (DEM) using 1/128 gridded Mars Orbiter Laser Altimeter (MOLA) helped us to extract the 26 basins and sub-basins drainage divides From these measurements, our study shows: (1) that all the drainages basins of a large region seem to cease their main fluvial activity at the same time at the end of the Early Hesperian epoch (~3.54 Gyr); (2) that the basin technique is the most reliable technique to do global age-dating; and (3) that there is a possible correlation between the degradation rate and the elevation. Our conclusions suggest that the main fluvial activity ceased because of a global climate change. We suppose that most of valley networks on Mars we observed today formed during the Early Hesperian and post-dated the early and late Noachian topographic features.