Here’s a color-composite image of Rhea and Titan, Saturn’s largest moons. Made from raw images acquired by the Cassini spacecraft on June 16, 2011, this really shows the vast difference in size and appearance of the two moons.
Rhea, seen in the foreground, is an icy, airless and heavily-cratered world 950 miles wide. Titan, on the other hand, is over three times larger at 3,200 miles across and covered in a thick atmosphere of methane and hydrocarbons. Its surface features mountains and valleys, with lakes and streams of liquid methane… and it may even have a liquid subsurface ocean.
Titan’s atmosphere and high-level haze can be seen in this image, and you can also see where the moon’s shadow cuts through the haze at the south pole (up and to the right in this image.)
Raw images taken in red, green and blue visible-light channels were combined to make this color version. The spacecraft was 1,828,949 km (1,136,456 miles) from Rhea when the images were taken.
Credit: NASA / JPL / Space Science Institute. Edited by Jason Major.