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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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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. Nature479, 53-60 (2011) doi:10.1038/nature10582


Timeline of major processes in Mars history.

BL Ehlmann et al. Nature479, 53-60 (2011) doi:10.1038/nature10582


Stream properties
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


Flowing water
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


Rills, Gullies and Streams

  • Sheetwash causes erosion

  • Channels form and grow headward



Water drainage
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






Evolution of a

meandering stream

system


Evidence for past water

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




Amazonian (<3 Ga) Valley Networks

Implication: 90% of VNs formed in the 1st billion years of the planet’s history.



Main evidence for a warm and wet ancient mars
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



There are abundant

channels on Mars


Some really convincing evidence of surface flow

NE Holden Crater Delta

MOC NA images


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


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




Comparison of old and new data

MGS data and newly recognized VN

Viking MDIM and Carr VN


Newly recognized VN from MGS

Carr VN on Viking base


Numerous VNs head near divides recognized as an integrated drainage system (yellow).

Centered near

1ºS, 22ºE


How long and recognized as an integrated drainage system (yellow).

when was Mars

Humid?

Arid early on...

Extended humidity

As it appears today


Fossil dendritic drainage channels recognized as an integrated drainage system (yellow).


Outwash channel recognized as an integrated drainage system (yellow).


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


medial ridge load

older, degraded channel system

different

flow paths





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