Cassini, which has been orbiting Saturn since 2004, discovered jets of water ice and organic particles shooting out from Saturn’s moon Enceladus in 2005. Scientists thought the amount of the spray changed over time but they couldn’t show until now that the spray changed in a pattern that could be easily recognized. After using infrared data from Cassini’s visual and infrared mapping spectrometer (VIMS) and other data gathered over time they were able to see the changes and recognize a pattern. When Enceladus is closer to Saturn the stronger gravitational pull of the planet makes the openings smaller and therefore less is sprayed out. (Look at the south pole of Enceladus in the picture below-right insert.)When Enceladus is further away from the planet less gravity allows larger openings so the spray escapes in larger quantities.
Enceladus has the most spray when it is farthest away from Saturn in its orbit (left insert) and the least spray when it is closest to Saturn (right insert).