Sixth International Conference on Mars (2003) 3045.pdf WARREGO VALLES REVISITED USING MGS AND ODYSSEY DATA: VALLEYS FORMED BY PRECIPITATIONS? V. Ansan and N. Mangold, Orsay-Terre, FRE2566, CNRS et Université Paris-Sud, Bat. 509, 91405 ORSAY Cedex, France,
[email protected]. Introduction: Different processes have been in- Local observations on MOC images: MOC high volved to explain valley networks: (1) Fluvial surface resolution images provide local information on the runoff formed by precipitation, (2) Groundwater sap- shape of valleys. Valleys are mantled by smooth mate- ping, (3) water-lubricated debris flows, (4) groundwa- rial, likely dust eolian material. This mantling is dis- ter flow (5) runoff formed by geothermal and/or tec- sected in many locations in small pits of several meters tonic activity. Surface runoff could explain the strong deep (Fig. 2). The latitude of Warrego at 40°S corre- erosion of Noachian craters [1], but surface runoff has sponds to latitudes at which dissected layers due to ice- been criticized because of the low drainage density [2] rich material is observed [5]. This layer affects signifi- and alternative hypothesis have been proposed in cold cantly the original depth of valleys. Measurements of climate [3]. Flows sustained by regional hydrothermal valley depth need therefore to be achieved with cau- activity have been involved especially for the Thauma- tion, especially if compared to other valleys which are sia region in which Warrego networks because of the not affected by same processes like in equatorial re- association of runoff sources with old volcanoes and gions. Furthermore, the filling of valleys makes the fault zone [4].