September 18, 2017 – Cassini bids farewell to Saturn’s yin-and-yang moon, Iapetus. This image is from the last set of observations Cassini made of this world of striking contrasts. The spacecraft helped scientists better understand Iapetus, solving a centuries-old mystery of why it should be bright on one side and dark on the other.
Cassini observations of Iapetus (914 mile or 1471 kilometers across) support the prevailing theory that led to the understanding that the dichotomy of the surface is due to a combination of infalling dust from outside of the moon followed by a migration of water ice from the darker (therefore warmer) areas to the cold, brighter surfaces.
This false-color view is a composite of individual frames obtained using filters sensitive to ultraviolet (centered at 338 nanometers), green (centered at 568 nanometers) and infrared light (centered at 930 nanometers). The view has been enhanced to accentuate subtle color differences and fine-scale surface features.
This view looks toward the Saturn-facing hemisphere of Iapetus. North on Iapetus is up and rotated 12 degrees to the left.
The view was acquired at a distance of approximately 1.5 million miles (2.5 million kilometers) from Iapetus. Image scale is 9 miles (15 kilometers) per pixel.
The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colorado.