A Color-Saturated Look At Mercury's Massive, Ancient Caloris Basin
Adam Rifkin stashed this in Astronomy Pics
Mercury's Caloris Basin is seen in an enhanced color mosaic. The massive crater, formed some 4 billion years ago, is orange. Smaller craters made subsequently are rendered in blue, while orange splotches around the perimeter may be volcanic vents.
(Side note: Props to the punster who titled the photo "All About that Basin" on the Jet Propulsion Laboratory's Photojournal page.)