Phobos striations - what are they?

It looks like it will be another six months before the Mars
Reconnaissance Orbiter (MRO) completes its aerobraking maneuvers. But
pictures of Phobos and Deimos on the MRO website -

http://marsprogram.jpl.nasa.gov/facts/phobos.html
http://marsprogram.jpl.nasa.gov/facts/deimos.html

- and some recent reading on Roche limits -
http://en.wikipedia.org/wiki/Roche_l...ected_examples

- reminded me of the striations seen on Phobos but not Deimos.
See http://marsprogram.jpl.nasa.gov/facts/phobos.html

According to the Wikipedia entry on Roche limits, Phobos orbits within
its fluid Roche limit for Mars:

Body | Rigid Roche Limit | Fluid Roche Limit
Phobos 172% 89%
Deimos 451% 233%

Maybe this explains the horizontal striations seen on Phobos? Or is
there a consensus explanation of the Phobos striations from the
professional astronomers?

- Canopus56