NASA's Cassini spacecraft will be gliding low over Saturn's moon Enceladus for a gravity experiment designed to probe the moon's interior composition. The flyby, which will take Cassini through the water-rich plume flaring out from Enceladus's south polar region, will occur on April 27 Pacific time and April 28 UTC. At closest approach, Cassini will be flying about 100 kilometres (60 miles) above the moon's surface.
Cassini's scientists plan to use the radio science instrument to measure the gravitational pull of Enceladus against the steady radio link to NASA's Deep Space Network on Earth. Detecting any wiggle will help scientists understand what is under the famous 'tiger stripe' fractures that spew water vapour and organic particles from the south polar region. Is it an ocean, a pond or a great salt lake?
The experiment will also help scientists find out if the sub-surface south polar region resembles a lava lamp. Scientists have hypothesised that a bubble of warmer ice periodically moves up to the crust and repaves it, explaining the quirky heat behaviour and intriguing surface features.
The Cassini-Huygens mission is a cooperative project of NASA, 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 Cassini-Huygens mission for NASA's Science Mission Directorate in Washington. The Cassini orbiter was designed, developed and assembled at JPL.