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Stream Channels

Stream Channels. There is some overlap of Earth and Mars surface conditions. Worst of Mars. Worst of Earth. Evolution of aqueous environments during the first billion years of Mars history. BL Ehlmann et al. Nature 479 , 53-60 (2011) doi:10.1038/nature10582.

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Stream Channels

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  1. Stream Channels

  2. There is some overlap of Earth and Mars surface conditions Worst of Mars Worst of Earth

  3. Evolution of aqueous environments during the first billion years of Mars history. BL Ehlmann et al. Nature479, 53-60 (2011) doi:10.1038/nature10582

  4. Timeline of major processes in Mars history. BL Ehlmann et al. Nature479, 53-60 (2011) doi:10.1038/nature10582

  5. Stream Properties • Stream Gradient – ground slope • Generally steeper at the HEAD • Very shallow at the MOUTH • Variable along the central length • Affects water velocity and volume • BASE LEVEL – lowest level of erosion • DISCHARGE – volume x width x area • Affects SEDIMENT LOAD • Amount of material being moved

  6. Flowing Water • Following rain events (melting events) • Overland flow / sheetwash • Streamflow – channels begin to form • Streams – general passage for water flow • Rill, creek, stream, river – size-based • Channel – passage-way of water flow • Banks – side walls of channel

  7. Rills, Gullies and Streams • Sheetwash causes erosion • Channels form and grow headward

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  9. Water Drainage • Ultimately, all water returns to the oceans • Drainage systems • Basins – areas collecting water into one main channel • Drainage basins – geographic zones • Divides – high elevations separating basins • Continental divides – largest basins directing water to the oceans

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  14. Evolution of a meandering stream system

  15. 500 km 10 km Evidence for Past Water Viking Orbiter image • The current thin, cold atmosphere prohibits liquid water from being stable on the surface. • However, there is ample evidence for past water • 3 flavors of flowing surface water: • Valley Networks (really old) • Outflow Channels (pretty old) • Gullies (really young) MOLA topography

  16. Martian Gullies

  17. Global Distribution of Valley Networks

  18. Amazonian (<3 Ga) Valley Networks Implication: 90% of VNs formed in the 1st billion years of the planet’s history.

  19. How big?

  20. Main evidence for a “warm and wet” ancient Mars • Valley networks • clear evidence of erosion by water • there has been a long standing debate over the importance of surface runoff vs. groundwater processes • more recent works show that precipitation was required to form many of the features • Widespread highland erosion (up to a km of crust lost) • Recently identified chemically weathered components of the crust (TES and OMEGA instruments) • hematite deposits in limited locales • sulfate deposits seen in many settings on Mars • clays (phyllosilicates) also detected • Mars Exploration Rovers show clear signs of groundwater interaction and possible signs of standing bodies of water

  21. Outflow Channels of Mars • Formed from catastrophic release of groundwater in mid to late martian history.

  22. There are abundant channels on Mars

  23. Some really convincing evidence of surface flow NE Holden Crater Delta MOC NA images

  24. Where did all the water go? • Deuterium/hydrogen ratios show that Mars (and Venus) lost most all of their water to space. • For Mars, the remaining water is tied up in the subsurface and polar caps Venus Ref: Owen and Bar-Nun, in R. M. Canup and K. Righter, eds., Origin of the Earth and Moon (2000), p. 463

  25. Strahler [1958] stream order classification 1 1 1 1 1 2 2 2 1 1 2 3 downslope 3 * Higher stream order corresponds to more mature drainage systems and more contribution from surface runoff

  26. blue = previously recognized valley networks by Carr [1995]

  27. Additional valley networks seen in MGS data

  28. Comparison of old and new data MGS data and newly recognized VN Viking MDIM and Carr VN

  29. Previously mapped unconnected valleys (blue) are now recognized as an integrated drainage system (yellow). Newly recognized VN from MGS Carr VN on Viking base

  30. Numerous VNs head near divides Centered near 1ºS, 22ºE

  31. How long and when was Mars Humid? Arid early on... Extended humidity As it appears today

  32. Fossil dendritic drainage channels

  33. Outwash channel

  34. Water flowing creates cross-bedded structures with sediment load It is likely that there was some flowing water on Mars, at least early on in its history Gusev Crater

  35. medial ridge older, degraded channel system different flow paths

  36. On the Titanian Coast...

  37. Valley networks!

  38. A channel on Titan...

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