Cochise College sponsored

              Mars- Mawrth Vallis  
      Circular Features in the Light-colored Deposits
                within the High Resolution Strip Area
return to high resolution strip overview
return to Mawrth Vallis index page    
The central portion of the high resolution strip is where
most of the light-colored outcrops occur.  At first glance,
the area seems to be rather unexciting.
inclined view of central area

     However, upon closer inspection there is a large number of
faintly visible circular features.  Their circular shapes imply a
meteorite impact origin, but there are no rim deposits and
there is no central depression, just a flat surface.
inclined view

An overall vertical view of the entire the high resolution strip, showing
the distribution of light-colored deposits and circular features.

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.)

Example 1
Example 2
Example 3
Example 4
Example 5
Example 6

Example 7
Example 8
Example 9

Example 10
Example 11
Example 12

 Also visit: Cochise College Mars Landforms , Mars Explored, 
Cochise College Geology Home Page
 Roger Weller, geology instructor (  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.