Written by Jia-Rui C. Cook
NASA’s Jet Propulsion Laboratory
Pasadena, CA – NASA’s Cassini spacecraft successfully flew by Saturn’s moons Enceladus and Dione during close flybys on May 2nd, 2012, capturing these raw images. The flybys were the last close encounters of these icy moons that Cassini will make for three years.
Cassini flew by Enceladus at an altitude of about 46 miles (74 kilometers). This flyby was designed primarily for the radio science sub-system to measure variations in Enceladus’ gravity field.On approach to Enceladus, Cassini’s cameras imaged the icy satellite’s south polar plume, which consists of jets of water ice, water vapor and organic compounds sprayed into space from the moon’s famed “tiger stripe” fractures.
The plume images were captured at distances ranging from 259,000 miles (416,000 kilometers) down to 66,000 miles (106,000 kilometers) when Enceladus was just a thin crescent and the plume was backlit.
During closest approach, the radio science team looked for a concentration of mass at the south pole that could indicate sub-surface liquid water or an intrusion of warmer-than-average ice that might explain the intriguing geologic activity at the south pole.
After the closest approach, the composite infrared spectrometer obtained a map of Enceladus’ sun-lit side while Cassini’s visible light cameras rode along and captured several images of the moon’s leading hemisphere at resolutions of about 1,500 feet (450 meters) per pixel.
Shortly after passing Enceladus, Cassini had a non-targeted encounter of Dione. At closest approach, the spacecraft flew within about 5,000 miles (8,000 kilometers) of the moon. Cassini’s cameras captured several mosaics during this encounter, including one taken around the time of closest approach that covered a fracture named Latium Chasma at resolutions of about 175 feet (53 meters) per pixel.
Other mosaics cover much of Dione’s northern hemisphere that faces away from Saturn in its orbit, focusing particularly on the moon’s ridges, an ancient impact basin and the wispy streaks that Cassini scientists now know are tectonic fractures.
On March 9th, 2013, Cassini will make a close pass by Rhea, but the spacecraft won’t have another close, targeted encounter with any of Saturn’s other icy satellites until June 2015, when it encounters Dione. Cassini will make its next flyby of Enceladus on October 14th, 2015.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency, and the Italian Space Agency. NASA’s Jet Propulsion Laboratory, Pasadena, CA, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The imaging team is based at the Space Science Institute, Boulder, CO JPL is a division of the California Institute of Technology, Pasadena.