NASA's Cassini Discovers the Space Between Saturn's Rings Is Empty

Saturn. Cassini finds the region between the planet's rings is a big, empty space. NASA/JPL-Caltech/Space Science Institute

NASA scientists have dubbed the space between Saturn's rings "the big empty," after gaining readings from the Cassini spacecraft. During the first of its final dives, Cassini revealed the void between the rings is largely dust-free, much to the surprise of scientists analyzing the results.

Cassini ventured into the space between Saturn's rings on April 26—the first in a sequence of dives that mark the mission's grand finale. Scientists from NASA's Jet Propulsion Laboratory want to find out how much dust there is in the environment between Saturn's rings as this will help them plan whether the spacecraft uses its antennae as a protective shield, meaning it would change when it could make observations.

If the environment were very dusty, scientists would hear a lot of crackling and popping in the readings—the sound of dust hitting the spacecraft. This would mean Cassini needed to shield its equipment for future maneuvers. However, as Cassini entered the 1,200-mile-wide void, scientists heard very little.

William Kurth leads the team in charge of the Radio and Plasma Wave Science (RPWS) instrument, which detects particles as it crosses through Saturn's environments. "It was a bit disorienting—we weren't hearing what we expected to hear," he said in a statement. "I've listened to our data from the first dive several times and I can probably count on my hands the number of dust particle impacts I hear."

For comparison, NASA released the recording of when Cassini crossed one of Saturn's faint dusty rinks in December 2016. In this recording, particles hitting the spacecraft can be heard clearly.

Cassini project manager Earl Maize said: "The region between the rings and Saturn is 'the big empty,' apparently. Cassini will stay the course, while the scientists work on the mystery of why the dust level is much lower than expected."

Understanding how dusty the environment is between Saturn's rings will now help researchers prepare for the next 21 dives. Four of these will require a protective shield to be erected around Cassini, but for the others, the instruments should be safe from large particles hitting and potentially damaging them.

In April, the spacecraft made the notable revelation that one of Saturn's moons could provide a source of energy for microorganisms—according to astrophysicists, the observation that Enceladus is releasing hydrogen means it is a good place to look for signs of life.

Cassini's next dive between Saturn's rings will take place Wednesday when it will enter a region close to the April 26 maneuver. Results from this are expected on May 3. The mission will come to an end on September 15, when the spacecraft will plunge into Saturn's atmosphere, where it will break apart and burn up.

Saturn atmosphere
An image from Cassini of Saturn's atmosphere. NASA/JPL-Caltech/Space Science Institute.