Cassini's days are numbered. But just because it's running out of fuel doesn't mean it's running out of fire.

From now until its final crash into the planet, Cassini will be collecting information about Saturn’s gravitational and magnetic fields, the composition of its upper atmosphere, the weight and age of its rings, the depth of its metallic hydrogen core, and more.

The manner in which particles and tiny moons accumulate in Saturn’s elegant rings, in particular, could tell us a lot. “That’s so key to understanding how Saturn formed,” said Linda Spilker, Cassini project scientist. Comparing these measurements to what NASA’s Juno spacecraft is collecting from Jupiter (also a gas giant) could help scientists put together a better picture of how solar systems form.

The team wants to know about the rings’ future, too. “We’re slowly losing the rings,” said Jim Green, NASA’s planetary science division director. “That material is filtering down into the planet. If you’ve ever eaten Jell-O, and you shake it, it shakes for quite a while before it settles down. Saturn was made 4.5 billion years ago, and it’s still shaking. We see that because the rings shift a little bit. So the seismic motion produced by the planet disturbing the rings produces the instability necessary for the rings to slowly fall into the planet.”

Saturn’s magnetic field is also an enigma; the Cassini team will analyze it from a variety of orientations to understand its source and depth. In addition, they’ll study Saturn’s dazzling pink aurorae. As particles rain down into the regions where we see aurorae, they emit radio waves, known as Saturn Kilometric Radiation, or SKR for short. These radio waves and the aurorae are complementary in that they’re both affected by the planet’s magnetic field.

By scrutinizing magnetic field data, the team hopes to be able to provide more info to scientists searching for and studying exoplanets. “The more we learn about our own solar system and under what conditions that happens, the more we’re going to be able to apply it all over the place,” Green said.

How is Green feeling after all of the excitement? “Watching it on the other side of all this, the tension and the build-up, it’s just an enormous relief,” he said. “We’re ready now for the next step.”

Spilker echoed the sentiment. “Probably the things we haven’t heard of will be the most spectacular,” she said.

Photo credit: NASA/JPL-Caltech/Space Science Institute

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