Geology of the Common Mouth of the Ares and Tiu Valles, Mars

Abstract

Since the Mars Pathfinder landing site is located at the mouth of the Ares and Tiu valles, this region attracts keen scientific interest. In order to better understand experimental data from this small area of the surface of Mars, which has been investigated by the rover, and the properties of the materials occurring here, it is necessary to answer how, from where, and when this material was transported. To answer these questions, we performed photogeological mapping and counted impact crater in the region. A photogeological analysis of 320 TV images of the studied area, thermal-inertia maps, and digital elevation models were used in mapping. Our results, and those published by other scientists, allow us to distinguish several principal stages in the geological history of the mouth of the Ares and Tiu valles: the destruction stage of an ancient plateau and three stages of fluvial activity. Deposits transported by water flows to the Mars Pathfinder landing site presumably consist of fragments of the material of ancient Martian highlands (impact breccias and lavas), of younger sedimentary or volcano-sedimentary material of ridged plains, of impact-crater materials, and of eolian products. The main constituents should be as old as approximately 4 Gyr (highland materials) and 3.5 Gyr (ridged-plain materials). It is very likely that the fluvial reworking of this ancient material took place between 3.6 and 2.6 Gyr ago and, possibly, even later, between 2.3 and 1.4 Gyr ago.