"As I’ve pointed out before, most of Mars is covered in basalt, a blue-gray rock. When you hear about sand on Mars, it’s usually coarse-grained stuff made up of eroded basalt. However, there’s also much finer-grained dust which is high in iron oxide – rust – and it’s that which gives Mars its characteristic ruddy color.
That fine dust covers everything, making the planet red/orange/ochre. But there’s wind on Mars, and it can blow the dust around, revealing the grayer basalt underneath (like the dust devils do). And if there’s no natural wind, why, the thrusters from the rockets of a sky crane hovering over the surface as it lowers a one-ton rover to the ground will do just fine.
That part is actually pretty obvious in the picture. The thrusters blew around the dust, revealing the rock underneath, giving the landing site a bluer cast in the image (remember, it’s color enhanced)."
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