I have an 8-inch telescope but can see only Mars as orange instead of red. All other planets appear colorless. Why?
Ed Lastella, White Plains, New York
Of the five naked-eye planets, only Mars has a noticeable color through a medium-sized telescope. And, although we refer to it as the Red Planet, your perception of it as orange is correct. Mars' color originates from several types of iron oxides (including hematite, ferrihydrite, and goethite) that blanket the planet's surface.