Topographical relief of the river-like feature on Mars.
By Evan
The National Post has put up some of the latest ESA pictures that reveal Mars’ glacial past. Included is a large, 7 km wide river valley, and what appears to be a cirque, a mountain scooped out by a glacier. The river valley shows evidence of braided streams, which are common in glaciated regions. As noted by some of the commentators, this feature is relatively young on the Martian surface, and there are few craters that have damaged the geomorphology.
Martian cirque?
A cirque near Jasper, Alberta (I apologize for the darkness, I need a better camera!).
A glacially related river bed on Mars? The ESA scientists believe the linear-style features formed long after water flowed to create the valley, possibly by glacial activity.
A braided stream in the Icefields Parkway in Alberta (if you ever get the chance to go to Alberta, it is one of the most amazing places on Earth). These are broad, sinuating rivers that originate from melting glaciers, and are constantly evolving.
What would be the composition of these glaciers. Only water, or with some component of CO2, like the martian ice-caps? Also, I thought that braided streams tend to be a feature of recently glaciated areas on earth because of the lack of vegetation. The geological record on Earth has braided streams more frequently before the Devonian and the greening on the continents. Given the lack of trees of Mars, I’m not convinced about the braided streams being a diagnostic of glacial activity.
I guess you are right Nick, though the sheer width of the river bank does indicate generally low energy flow conditions (it is pretty flat at the bottom), punctuated by high flow rate events (to create such a deep channel), similar to a braided stream. Note that the idea that it is a braided stream is just something I threw out there as a potential cause of formation, ESA didn’t suggest an initial cause.
I found from a quick Google search that solid CO2 is 10 times weaker than water, so it could possibly flow pretty fast, maybe creating a carbon dioxide enhanced glacier that causes erosional effects that look similar to river beds if the concentration was high enough. That same study suggests it is unlikely that solid CO2 could be very stable over geological time because it is so weak. Given the size of this channel, whatever created it probably had to persist for a reasonably long time. If Mars was pretty cold when this channel formed, maybe that could be an answer.
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