The Colors of Mars

While Mars has long been considered the “Red Planet”, does that mean that even NASA’s blue “meatball” logo has to turn hot pink? Shifting, unusual colors have been the topic of considerable online discussion since NASA’s Mars Exploration Rovers landed on the planet last month. Some, for example, point to images of a color calibration target on each rover: squares that should appear green and blue, such as in this image, instead appear brown and pink. Is this evidence of a problem with the rovers, a simple technical goof, or something more nefarious? As you might image, conspiracy theorists have tended to focus on the last explanation.

Tuesday’s New York Times provides the clearest and most succinct explanation for the shifting colors. Scientists create the color images by combining grayscale images taken through different filters. For “true color” images, scientists usually use images from green, blue, and red filters, but in many cases the red filter has been replaced with a near-infrared one. The result: blue turns to pink. Why the switch? The infrared filter allows scientists to discern several types of minerals in the rocks and soil.