Science@NASA: Cassini’s Finale

August 15, 2017
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NASA’s Cassini mission will come to a spectacular close on September 15, 2017 at 5:07 a.m. PDT after almost two decades in space since its launch in 1997. The spacecraft has been orbiting Saturn and studying that system for 13 years. It’s now checking off items from a daring bucket list as it makes the most of its final months.

Since its arrival at Saturn in 2004, Cassini’s stunning observations of Saturn, its rings and moons, and the surrounding space have produced a series of extraordinary discoveries. Cassini confirmed the presence of huge lakes on the moon Titan’s surface containing liquid methane and ethane. This makes Titan the only body in the solar system, other than Earth, that has bodies of standing liquid on the surface. Cassini also caught the moon Enceladus spewing plumes of water vapor, icy particles, and organic compounds through fissures in its frozen outer shell known as Tiger Stripes. In addition, the mission showed that Saturn’s rings are an active and dynamic system that can serve as a ‘laboratory’ for scientists to study how planets form.

The spacecraft has finished a series of 20 pole-crossing orbits between the gas giant’s outer F and G rings, making new discoveries about the rings and the moons that orbit in the outer rings. Cassini is now in the process of executing 22 daring ‘Grand Finale’ dives that are bringing it closer to Saturn than any spacecraft has gone before—in the 1,200-mile gap between Saturn and its innermost ring. Initial orbits have already produced a surprising discovery—that it’s relatively empty between the planet and its rings.

The images and data gathered during these maneuvers will add to the knowledge Cassini has already provided about how giant planets – and planet families throughout our universe -- form and evolve. Researchers will be able to map Saturn’s gravity and magnetic fields near the planet in detail, revealing new clues about the planet’s internal structure. They believe that it’s not as simple as a core of ice and rock with a huge envelope of hydrogen/helium on top. These final data will also greatly enhance what Cassini has already shown us about the age and origin of Saturn’s rings and how much dust and ice they consist of.

The conclusion of the “Grand Finale” comes when Cassini performs an epic final plunge into the gas giant’s upper atmosphere. The spacecraft will transform into a fiery streak in Saturn’s skies, removing the chance of a contaminating collision with any of Saturn’s icy moons – and bringing a long, rich mission to a dramatic close.

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