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Opposition Effect Glow on Mars

This panorama of Phoenix Mars Lander images was made to show nearby rock sizes. It shows something else - an opposition effect glow.

The area around the camera shadow (red arrowed) is noticeably brighter. The camera shadow marks the antisolar point directly opposite the sun. Notice how the rock shadows all point there. Close to the point the shadows are very short and are hidden from the camera by the rocks themselves - the area thus looks brighter.   Minerals in the rocks might also retro-reflect and a further effect called coherent backscattering contributes to opposition glows. One thing we can be sure of, there is no Heiligenschein produced by water drops!

Mars is brighter in our skies at opposition for these reasons, and hence the name. We see a similar effect on the moon and asteroids.

Another Martian opposition glow     Opposition glow on Earth