a closer view of the central area with the light circles high-lighted
The circular features are very faint and only be seen by
exaggerating contrast. The features are identified by curving
fractures, density of fracturing that is different than the
surrounding area, and by a change in coloration.
an example of a circular feature
From a previous section it was discovered that the
light-colored layer was originally covered by a thick layer
that was eroded away. The exposed light-colored layer
represents an eroded surface that shows fractured bedrock
clear of Martian dust.
It is not possible at this point to say whether the white
layer was eroded before it was buried by a thick layer of
darker materials or it was eroded flat after the overlying
layers were removed.
The light-colored deposits must be somewhat durable
because there are no light-colored dunes in the area.
Some of the light was probably eroded away and deposited
on a shelf adjacent to Mawrth Vallis and some light-colored
material was deposited on the floor of the main channel.
One possible cause for the fractured circular features is
that the now-eroded dark layer absorbed meteorite impacts
but the craters did not penetrate down to the light-colored
deposits. Instead, the shock wave from the impacts fractured
the light-colored material but did not produce craters.
Examples illustrating the fractured circular features.
It must be emphasized that these circular features are
very faint in the original photographs.
(All of the following views have been photographically enhanced in contrast and
resolution in order to emphasize features.)
Also visit: Cochise College Mars Landforms , Mars Explored,
and Cochise College Geology Home Page
Roger Weller, geology instructor (email@example.com) last edited: 11/2/15
All views were derived from Google Mars and were originally obtained from
the United States Geological Survey (USGS), jet Propulsion Laboratory (JPL)
and the University of Arizona.