After accounting for lighting variations and viewing angles in the images, which were taken between 2005 and 2012, Hedman and colleagues found that when Enceladus was farthest from Saturn its plumes were three times brighter than when it was closest.
On average, Enceladus circles about 148,000 miles (238,000 kilometers) from the center of Saturn. Its closest and farthest approach differ by less than 1 percent, or about 1,243 miles (2,000 kilometers.)
The analysis indicates that the fissures, which scientists nicknamed "tiger stripes," open wider when the tidal forces are strongest, allowing more material to escape. On average, the cracks, which are warmer than the surrounding area, are about 80 miles (130 kilometers) long, 1.2- to 2 miles (2- to 3 kilometers) wide, and about 1,650 (500 meters) deep.
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"Different theoretical models made different predictions for how the cracks might open and close or heat up and cool down as the moon goes around the planet," Hedman said. "With this information we're in a position now to confront those models with real data."