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| Titel |
Evolution of valleys width : A Mars-Earth comparison |
| VerfasserIn |
Stéphane Pochat, Nicolas Loget |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250074484
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| Zusammenfassung |
| The analyses of the valleys on Mars are used to reconstruct the climate on Early Mars (~ 3.5
Gy). Thus, many studies indicate a strong analogy between earth and mars networks
(dendritic organization, drainage density Strahler ordering) which is compatible with a
widespread rain (today Mars is arid, cold and the water can only be vapor/snow). But, many
features are too different with the Earth classic valleys networks to conclude definitively on
the Early climate of Mars.
Here, we study the evolution of the width of valleys with drainage area. This
method lies on the relationship between the evolution of the channel width (W) versus
the discharge of the river or the upstream drainage area (A) such as Wc= bA0.5
(e.g Leopold and Maddock, 1953; Montgomery and Gran, 2001). On Mars, one
of the difficulties is to plot the width of the channel but recent studies on Mars
and on Earth indicate that the valley bottom width Wv strictly follows the same
evolution than the channel width (e.g. Mattheus and Rodriguez 2011, Phillips,
2011).
Thereby, we analyzed 366 basins on Earth from 4.10-02 to 6.1006 km2 and 355 basins on
Mars from 7.10-02 to 2.8.1006 km2. For Earth Wv= bA0.46 with 0.005< b< 0.047. For
Mars Wv= bA0.27 with 0.046< b< 0.19. Martian valleys are ten times wider for
small tributaries (< 100 km2) but ten times smaller for large tributaries >100.000
km2).
Our observations are compatible with an inefficient system with strong supply of water,
on small systems, which is less and less transmitted at the outlet, on large systems. The
origins of this inefficiency will be discussed.
Leopold, L. B. and T. Maddock (1953). The hydraulic geometry of stream channels and
some physiographic implications. United States Geological Survey Professional
Paper.
Montgomery, D. R. and K. B. Gran (2001). "Downstream Variations in the Width of
Bedrock Channels." Water Resour. Res.
Jonathan D. Phillips (2011): Drainage area and incised valley fills in Texas rivers: A
potential explanation. Sed. Geol.
Mattheus and Rodriguez (2011) Controls on late Quaternary incised-valley
dimension along passive margins evaluated using empirical data. Sedimentology. |
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