White Ridges on Mars

What created these white ridges on Mars? The images showing the white ridges,
including some of the highest resolution images ever taken from Martian orbit,
were recorded last year by the Mars Reconnaissance Orbiter (MRO). A current
leading hypothesis is that the white ridges formed as water flowed through
underground cracks and bleached and hardened the edges of surrounding rocks.
Over millions of years, surface winds eroded the darker rock leaving the raised
white ridges. Such water-created light-colored markings are well known here on
Earth. The hypothesis is particularly interesting as underground water could have
helped to support microbial life on the red world. The above image resolves surface
features as small as one meter across in Candor Chasma region of huge Valles Marineris
on Mars.