Saturn is a bit of a moon hoarder. It has 62 known moons. It has so many moons, not all of them have even been named. Titan, with itsand , may get all the glory, but there are other moons around the gas giant that are fascinating in their own right. Astronomers have been studying the large icy moons of Mimas, Enceladus, Tethys, Dione, Rhea and Iapetus since long before we ever sent a human into space.
Thanks to NASA's Cassini spacecraft, we now have the best images of those moons in space history. We first got up close and personal with the moons when NASA's Voyager spacecrafts stopped by for a look in the early 1980s. Those images were often fuzzy and missing large sections of the moons' surfaces. Now, scientists have pulled together data and imagery from Cassini's 10 years of study to create a brand-new set of color maps showing the moons in much greater detail.
The colors in the Cassini maps have been enhanced to show details and highlight new discoveries about the moons. NASA notes, "The most obvious are differences in color and brightness between the two hemispheres of Tethys, Dione and Rhea. The dark reddish colors on the moons' trailing hemispheres are due to alteration by charged particles and radiation in Saturn's magnetosphere. Except for Mimas and Iapetus, the blander leading hemispheres of these moons -- that is, the sides that always face forward as the moons orbit Saturn -- are all coated with icy dust from Saturn's E-ring, formed from tiny particles erupting from the south pole of Enceladus."
The before and after maps of Enceladus are particularly interesting. The Voyager map shows large missing sections where the imagery is fuzzy and blurred. A few craters are noticeable, but the moon's surface is largely a mystery. Cassini's map, however, shows sweeping dune-like areas and recent fractures that are highlighted by a bluish color, a result of a strong ultraviolet signature. Scientists speculate that these fractures may hold large-grain ice that has been exposed to the surface.
The fresh maps are the work of Paul Schenk, a participating scientist with the Cassini imaging team at the Lunar and Planetary Institute in Houston. Schenk is a self-described "space-groupie since Gemini days."
The Cassini mission and the work of scientists like Schenk have created a treasure trove for space enthusiasts, bringing us ever closer to Saturn and its intriguing satellites. If you ever manage to hitch a ride to Tethys, be sure to pack Schenk's map so you can find your way around.