It’s official: The abyss between Saturn and its rings is empty. After Cassini’s first dive through on April 26, scientists confirmed that there is practically no dust in the gap, which has some puzzled.

“The region between the rings and Saturn is ‘the big empty,’ apparently,” Earl Maize, Cassini project manager, said in a release on May 1. “Cassini will stay the course, while the scientists work on the mystery of why the dust level is much lower than expected.”

The measurements came from Cassini’s Radio and Plasma Wave Science (RPWS) instrument, one of the long antennas that protrudes from the spacecraft. This instrument transmits a “ping” when dust hits it.

Cassini's  Radio and Plasma Wave Science instrument pings when dust interacts with it.  (RPWS) instrument

As expected, when Cassini flew inside the rings, there were several pings, which sound like pops and cracks over the usual eery whistling sounds, signaling a ton of dust. But, in the empty region, there were very few pings at all and the whistle remained clear.

You can hear the difference in these videos, here’s the sound within the ring gap:

And here’s the sound the RPWS makes when passing through a ring:

“It was a bit disorienting — we weren’t hearing what we expected to hear,” William Kurth, RPWS team lead at the University of Iowa, said. “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.”

The scientists even prepared Cassini for these dives by orienting its main antenna into a shield to block any oncoming particles. But, it seems now that it’s clear skies for the remainder of the most daring part of Cassini’s Grand Finale.

The spacecraft has 21 dives left, the second of which will be at 3:38 p.m. Eastern on Tuesday.

Photos via NASA/JPL-Caltech, Flickr / 2di7 & titanio44