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Cassini Survives Its Daredevil Plunge Toward Saturn

The craft’s first date with the “big empty” went off without a hitch

Looking toward the sunlit side of Saturn's rings, Cassini captured this image in violet light on Oct. 28, 2016. (NASA/JPL-Caltech/Space Science Institute)
smithsonian.com

When Cassini, the NASA spacecraft on a suicidal course toward Saturn, went offline last week, its chances of survival were anyone’s guess. Would the craft make it through a daring dip between Saturn and its famous rings? For hours, the probe was offline and out of radio contact. But at midnight Pacific time, it finally got back in touch. And now, reports the BBC’s Jonathan Amos, it’s clear that the last phase of its mission is going according to plan.

The feisty little craft successfully completed its first plunge toward Saturn in the space one NASA scientist is calling the “big empty.” It’s a previously unexplored region that Cassini will visit four more times during its so-called grand finale before it finally smashes into Saturn’s atmosphere. Shielded by its radio dish, reports Amos, the probe dove between Saturn and its iconic rings for the first time.

Until Cassini got back in touch, what was inside was anyone’s guess. Saturn’s rings are made of ice and rock of varying sizes, and mission control worried that the gap between the planet and its first band might contain particulate that could damage the craft. But oddly, once Cassini passed the band and plunged into the gap, it came across…not a whole lot.

In a press release, NASA says that the region between Saturn and its first ring appears to be “relatively dust free.” This result confused scientists, who expected a much higher amounts of dust. They’d used previous images gathered by the craft to rule out the possibility of big chunks that could damage Cassini, but figured that there’d be plenty of ring dust inside—dust that wasn’t visible to Cassini from a distance.

As the probe dropped into the seemingly empty space, it took photos and collected sound data that it later transmitted back to Earth. When dust or other particles hit the craft, they make a distinctive popping sound on the recording—and when Cassini crossed other ring areas in the past, scientists picked up plenty of snaps, crackles and pops. But this time, they didn’t hear much at all.

“It’s a bit disorienting—we weren’t hearing what we expected to hear,” says William Kurth, who leads the craft’s Radio and Plasma Wave Science instrument team at the University of Iowa, in the press release.

And that’s not necessarily a bad thing. All of the information Cassini will gather as it completes its grand finale of 22 total dives between the rings will be entirely new, since no craft has ever managed to pull off such daring moves. Scientists hope that the data about what’s inside will yield new insight into how Saturn and other planets formed and add to the body of knowledge about the ringed planet.

As Smithsonian.com reported last week, the sequence of dips and dives is only possible because the craft has already collected so much data over the last 20 years. As Cassini continues toward its final rendezvous with Saturn and its ultimate destruction, it’s leaving caution to the wind—and if the first dive’s data is any indicator, the rest of the mission’s final chapter might just go off without a hitch.

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