| Among
the many varied landscapes on Mars the term chaos is applied to those places
that have a jumbled, blocky appearance. Most of the better known chaotic
terrain occurs in the northern hemisphere but there are other occurrences
in the southern hemisphere, three of which are centered on ~180 degrees
west longitude. Ariadnes Colles, Atlantis, and Gorgonum Chaos all share
similar features: relatively bright, irregularly shaped knobs and mesas
that rise above a dark, sand-covered, hummocky floor. |
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Close
inspection of this THEMIS image shows that the darker material tends to
lap up to the base of the knobs and stops where the slopes are steep. On
some of the lowest knobs, the dark material appears to overtop them. The
knobs themselves are highly eroded, many having a pitted appearance. Images
from the camera on Mars Global Surveyor clearly show that the dark material
is sand, based on its mantling appearance and the presence of dunes. It
looks as though the material that composes the knobs was probably a continuous
layer that was subsequently heavily eroded. While it is likely that the
dark sand is responsible for some of the erosion it is also possible that
the this landscape was eroded by some other process and the sand was emplaced
at a later time.
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