The sound of a spacecraft passing between Saturn and its rings is straight out of 'Alien'

On April 26, NASA's Cassini spacecraft shot between Saturn and its innermost ring, going where no human-made object has gone before.

Cassini has already made some new discoveries thanks to its dive through the ring plane. One of those insights is that the area between the planet and its rings "sounds" different than other parts of space surrounding Saturn. 

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According to new audio files released by NASA, the 1,500-mile-wide gap between Saturn and its distinctive rings actually sounds pretty empty. 

Image: NASA/JPL-Caltech

Other parts of space around Saturn are filled with particles of dust that can be heard by Cassini's plasma detector. This instrument picks up the signal from dust that vaporizes as it hits the fast-moving spacecraft. 

But the gap between Saturn and its rings is comparitively, and unexpectedly, silent. 

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

Scientists compared data picked up from Cassini's ring dive and a previous pass through a faint ring of dust and debris on Dec. 18, 2016. 

The 2016 data sounds crackly, with a high number of plasma pops heard as Cassini passed through the ring itself. 

The data taken by the instrument late last month, however, sounds very different. 

Instead of crackly pops, the April data sounds more like static from a TV screen punctuated by a high whistling noise that, according to NASA, is a type of plasma wave that scientists are planning to investigate further.

"It was a bit disorienting — we weren't hearing what we expected to hear," Cassini scientist William Kurth said in the 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."

During that first ring dive, the bits of debris Cassini ran into were only about the size of the particles found in smoke, NASA said. 

Cassini is now in the last phase of its mission at Saturn. 

The spacecraft will continue to make dives through the gap between Saturn and its rings until the planned end of its mission in September, when it will make its death dive into the world's thick atmosphere. 

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