NOVA

For almost 13 years, the spacecraft Cassini has been in the Saturn system, documenting the planet and its moons. Cassini’s days are numbered—on 15 September, it will be sent hurtling towards Saturn. But just because it’s running out of fuel doesn’t mean it’s running out of fire. Cassini has a lot more science to do in its final chapter.

Out near Saturn, the spacecraft Cassini has just entered its final and riskiest chapter.

Out near Saturn, the spacecraft Cassini has just entered its final and riskiest chapter.

For almost 13 years, the spacecraft Cassini has been in the Saturn system, documenting the planet and its moons. Cassini’s days are numbered—on 15 September, it will be sent hurtling towards Saturn. But just because it’s running out of fuel doesn’t mean it’s running out of fire. Cassini has a lot more science to do in its final chapter.

Front Row Seat to Saturn

Space & Flight

Onscreen : Cassini. Take a look. It won't last long.Tracy Becker : Cassini is one of the most incredible spacecrafts, I think, that have ever flown.Jonathan Lunine : It is the most successful planetary exploration mission ever mounted.Onscreen : For nearly 13 years, Cassini orbited Saturn. Showing us methane lakes on Titan. Ice jets on Enceledaus. And a hurricane at Saturn's north pole. But Cassini's days are numbered.Becker : The spacecraft is running out of fuel.Onscreen : Today, Cassini's final—and riskiest—chapter begins.Lunine : Earlier this morning, Cassini entered its first grand finale orbit where Cassini is actually now no longer orbiting outside the rings of Saturn.Becker : This new orbit trajectory puts the spacecraft in between Saturn's atmosphere and the main ring system. But it does add a lot of risk. So a small particle could actually do a lot of damage because of the velocity that the spacecraft is traveling at.Onscreen : It's worth the risk to get new data. These images just came in this morning. They're of Saturn's atmosphere.John Blalock : These are just very nice images that have a lot of details of features we've seen at lower resolutions and look interesting but now we can really see them in very high detail and try to understand them a lot better.Kunio Sayanagi : What we saw before as wispy clouds are clearly streaky, cirrus clouds. And then puffy clouds are clearly convective, cumulus clouds. The polar vortex is basically like a hurricane on Earth. At the center of the polar vortex, there's a bright, really small cloud. That's definitely a surprise to me.Onscreen : That's not all. Cassini will soon tell us the mass of Saturn's rings.Becker : The mass of the rings actually holds the key into the origin and the evolution of the ring system to decide whether or not these rings must have formed within the last hundred million years or could have formed billions of years ago when Saturn formed.Onscreen : And it'll show whether the planet is all gas or has a core.Lunine : It's important because whether Saturn actually has a core or not tells us how it was built 4.5 billion years ago—how did it form?Onscreen : Which will reveal how other planets in our solar system formed too. And then, on 15 September, Cassini will hurtle towards Saturn. It'll sample the atmosphere as it falls. And then Cassini will burn up and go silent. Forever.

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