An injection of dispassion...
2 points:
It's worth extracting that piece of the image and playing with the contrast and intensity functions in photoshop or similar - that quite nicely resolves dark dust streaks within the gullies. They aren's shadows - wrong shape.
Also, as REB says, although not HOW he says it, with a sun angle to the horizon of 65 degrees, you need hill slopes of 65 degrees before you get a shadow. Most "steep" slopes on Mars are actually around 20 degrees!