[verum ago]

IMHO - you are looking at a slide on a talus slope. Nada mas. Unexposed material is now exposed; it is unweathered and unoxidized and brighter in appearance. It is probably high in iron.

I'm not going to pretend to know much about geology, but (a few IMHO's here) Mar's atmosphere is primarily CO2-- there should be essentially no oxidation taking place, meaning that the inside and outside of rocks and and the tope layer and inner body of a talus slope should be basically chemically identical (and therefore the same color). Also, the article notes that the tracks left by the Rovers, whirlwinds, and the interiors and ejecta of new craters have all been pretty consistently darker than the surounding, undisturbed material.

[kinsman redeemer]

Okay, then.

I give up. Being overwhelmed by facts and opinions of professionals, it is good to resign one's fallacious position and learn from the experience.