Probably seeing things ( Mars does that to you! ) but was looking at an image of white rock in Pollack crater, and there appears to be a low-lying but still raised plume of dark smoke issuing from the centre of a white rock outcrop ( see image PIA02849 on nasa's photojournal - it's a few years old ) The outcrop resembles an African mask, and the image has annotations on it. The 'plume' issues from the centre of the outcrop, and is shadowed on the lower edge, so must be raised. It blurs the boundary between the white rock and surrounding dunes as it drifts North-East. Can anyone see this, or am I having a Percival Lowell moment??