A t this WEB site there are some interesting pictures.

Click on the "Cydonia Face" this will take you to two pictures, a large area mapped out in long rectangles, which represents areas in close up.
The area in question is M18-006064. In this picture you will see some large tube like structures, some smaller and some very long.
Just as a joke I could say they look like the Giant Worms of Dune.

But-
Look at the shape of these worm like structures, it seams to have a kind of an arch like structure, the white areas of the worms. What could they be? Could not find any reference or explanation for them at that site.


Go to this web page:

http://mpfwww.jpl.nasa.gov/mgs/msss/camera/images/01_31_01_releases/cydonia/index.html