HR: 0800h
AN: P21B-0146    [Abstracts]
TI: Quantifying valley network parameters on Mars using DEM from HRSC/MEX data
AU: * Ansan, V
EM: ansan@geol.u-psud.fr
AF: IDES UMR 8418, bat 509 Université Paris Sud, Orsay, 91405 France
AU: MANGOLD, N
EM: mangold@geol.u-psud.fr
AF: IDES UMR 8418, bat 509 Université Paris Sud, Orsay, 91405 France
AU: MASSON, P
EM: masson@geol.u-psud.fr
AF: IDES UMR 8418, bat 509 Université Paris Sud, Orsay, 91405 France
AU: QUANTIN, C
EM: cathy.quantin@univ-lyon1.fr
AF: LST, Université claude bernard, Villeurbanne, 69622 France
AU: NEUKUM and HRSC team, G
EM: neukum@zedat.fu-berlin.de
AF: F U Berlin, Malteserstr. 74-100, Berlin, 12249 Germany
AB: Valley networks are ubiquitous in Martian, old, densely cratered terrains. They show a well developed branching-like pattern and are thus interpreted as the result of fluvial activity during the Noachian period (>3.6 Gy) despite other hypothesis such as subsurface flows. On the plateaus surrounding Valles Marineris, some well preserved dendritic valley networks have been identified, suggesting the same process of formation (fluvial activity). They show the same organisation as the Noachian valley networks but valleys appears much shallower than the former. Based on the cross-cutting relationships and crater counts, they are dated of the Late Hesperian time. The high spatial resolution (few 10 m/pixel) of HRSC images acquired with stereo-mode allows us to perform DEMs (Digital Elevation Model) on these areas to study quantitatively the two different kinds of valley networks. HRSC DEM have a spatial resolution of ~50 m and a height accuracy of 100 m. In HRSC DEMs, Noachian valley networks located in Aeolis region [157°E-30.5°S] show a great number of tributaries (few 100s) arranged in 5-6 Strahler's orders, with a drainage density close to 0.3 km-1. Lengths of major tributaries are few 100s km to 1000 km. The major tributaries are often 100-200 m deep. In contrast, the Hesperian valley networks that incised the plateau of Echus Chasma have much smaller number of tributaries (few 10s) arranged in 5 Strahler's orders with a drainage density close to 1. Lengths of major tributaries are few 10s km and the major tributaries are shallow less than 100 m deep. In the two studied examples, the valley networks show the same spatial organisation, e.g. dendritic pattern, which suggests that they formed by the same erosive process involving fluvial activity. The difference in depth and length suggests that the fluvial activity was more significant and efficient during the Noachian time eroding important volume of material and/or the fluvial activity was spending over a long period of time. As a consequence, the climate in the Noachian was highly warm during geological long duration to incise these valleys, whereas the Hesperian valleys have formed during shorter episodes of time enabling surface runoff.
DE: 5415 Erosion and weathering
DE: 5464 Remote sensing
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: Fall Meeting 2005