This view from NASA’s Opportunity Mars rover shows part of “Marathon Valley” as seen from an overlook north of the valley. It was taken by the rover’s Pancam on March 13, 2015. (NASA/JPL-Caltech/Cornell Univ./Arizona State Univ.)

Ask Ethan: Why Does Mars Have A Bright, Red Sky?

We know that it’s ‘the red planet’ because of the iron in its soil. But why, with such a thin, carbon dioxide atmosphere, is the martian sky so red and bright?

We can learn an awful lot about a world by looking at its atmosphere. On Earth, for example, the optical properties…