关于这张图
This VIS image of Olympia Undae was collected during north polar summer. The dunes are now completely frost free and are dark in color due to being made of basaltic sand. The surface between the dunes, where visible, is a bright tone. In some regions of dense dunes, the bright material may be a deposit on the dunes rather than the underlying surface. The presence of gypsum has been suggested for Olympia Undae, gypsum is a lighter tone than basalt in this filter of the THEMIS VIS camera. This VIS image hightlights the density of dunes, the bottom third of the image has fewer dunes, spaced farth…
