HR: 0830h
AN: P11B-1033    [PDF]
TI: Comparing Topography of Martian and Terrestrial Drainage Basins Using Integral-Geometry Morphological Image Analysis -- Implications for Origin of Martian Channel Networks
AU: * Stepinski, T F
EM: tom@lpi.usra.edu
AF: Lunar and Planetary Institute, 3600 Bay Area Blvd., Houston, TX 77058
AU: Coradetti, S
EM: scorad@mit.edu
AF: MIT, 77 Massachusetts Ave., Cambridge, MA 02139
AB: The origin of Martian channel networks located on Noachian terrain remains undetermined despite extensive studies. Whereas previous studies have focused on morphology of the channels themselves, we concentrate on topography of underlying drainage basins to diagnose an erosion process. DEMs based on the MOLA data (Mars, 500 m resolution) and the SRTM data (Earth, degraded to 450 m resolution) are used to delineate 28 Martian and 26 terrestrial drainage basins. Our analysis is based on the novel idea to use integral-geometry morphological image analysis to characterize quantitatively basin's topography. Each basin is represented by a 3-D digitize surface extracted from a DEM. The method is to ``scan" this surface by a large number of horizontal planes labeled by relative elevation $z$. Each plane divides basin's pixels into those above and below the plane producing a binary pattern that is characterized by the set of three numbers (Minkowski numbers: pattern area, $S$; its parameter, $U$; and its Euler characteristics, $\chi$). As different set of numbers is obtained for each scan, the overall output is the set of three functions that encapsulates the basin's topography. We combine these functions to define the ``compactness function" $\alpha(z) =4\pi S(z)/U^2(z)$. It has a large value for a compact, circle-like shape and a small value for an elongated shape. The range of $\alpha$ is from 0 (for a line segment) to 1 (for a circle). We have calculated $\alpha (z)$ for all basins and have observed a systematic difference between the character of $\alpha (z)$ for terrestrial and Martian basins. Terrestrial basins yield a characteristic, $\cal S$-shaped $\alpha$ functions indicating formation of elongated valleys at their lower regions. Morphology of terrestrial landscapes conforms to river networks. This points to maturity of terrestrial landscapes with respect to runoff erosion. Martian basins yield flat-shaped $\alpha$ functions reflecting a disconnection between landscape morphology and channel networks. This points to immaturity of Martian landscapes with respect to runoff erosion. Thus, our analysis suggests that Martian channel networks did not originated from the Earth-style, sustained surface runoff erosion, but, instead, were incised by a process having relatively small impact on the underlying surface. This requirement is fulfilled by erosion due to groundwater sapping, and, perhaps, it could be fulfilled by a surface runoff of limited volume and duration.
DE: 1625 Geomorphology and weathering (1824, 1886)
DE: 5415 Erosion and weathering
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: 2003 Fall Meeting