  Erosion by flowing water is one of the major forces shaping the surface of
Earth. Studies in the last decade have shown, in particular, that the drainage
region of rivers, where water is collected, exhibits scale invariant features
characterized by exponents that are the same for rivers around the world. Here
we show that from the data obtained by the MOLA altimeter of the Mars Global
Surveyor one can perform the same analysis for mountain sides on Mars. We then
show that in some regions fluid erosion might have played a role in the present
martian landscape.
