Mercury Mosaic (IMAGE) Arizona State University Caption This is a mosaic of images collected by MESSENGER as it departed Mercury on October 6, 2008. The Wide Angle Camera on MESSENGER imaged the surface through 11 color filters ranging in wavelength from 430 to 1020 nm. A principal component analysis of the 11 sets of images helps to highlight subtle color differences. The second principal component, first principal component, and a ratio of the 430 nm to 1020 nm wavelengths are combined here in a red-green-blue composite. Impact craters that formed relatively recently, such as Kuiper (62 km in diameter, yellow crater near center), have contrasting ejecta and rays because they excavated fresh material. As it sits on the surface, this fresh crater material will gradually alter its color until it matches the background material. Other impact craters, such as those with ejecta that appear blue in this color scheme, have color contrasts because they excavated compositionally distinct material from below the surface. Lermontov crater (152 km in diameter), near the top left, appears orange and is thought to contain pyroclastic deposits resulting from explosive volcanic activity in the past. Credit Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Arizona State University/Carnegie Institute of Washington Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.