Cassini captures pieces of Saturn’s rings
We can’t bring ‘em home, but we should be able to figure out what they’re made of
The soon-to-die Cassini probe has captured tiny fragments of Saturn’s rings. Cassini’s was launched in 1997, made it to Saturn in 2004 and has been there ever since. But the probe is running out of fuel and will be crashed into the gas giant in September 2017, in order to avoid possible contamination of potentially-life-bearing moons.
NASA has planned a series of swoops through Saturn’s rings for the probe’s “grand finale”. The space agency has little to lose – Cassini is going to die either on purpose or by bonking a boulder – so risky flights are now tolerable.
And worthwhile, too. NASA’s revealed that the probe’s obtained samples of Saturn’s atmosphere and rings.
“During Cassini's first two passes through the inner D ring, the particle environment there was found to be benign,” NASA writes. “This prompted mission controllers to relax the shielding requirement for one orbit, in hopes of capturing ring particles”. That plan worked – Cassini’s cosmic dust analyzer now has “many nanometer-size ring particles” to play with and a few weeks left to poke and prod.
We also have some gases from the outer reaches of Saturn’s atmosphere, with more to come as some of Cassini’s final orbits will again take it towards the gas giant’s clouds. It’s hoped the craft’s ion and neutral mass spectrometer keeps working during its death dive, to deliver even more information on the planet’s composition.
Cassini’s last days have also yielded news that “Saturn's magnetic field appears to be surprisingly well-aligned with the planet's rotation axis” – just 0.06 per cent off. This matters because we think planetary magnetic fields are caused by their liquid metallic cores sloshing around and the sloshing won’t happen without the magnetic field being tilted.
Saturn boffins are baffled and frustrated by this phenomenon because it means precise measurement of the length of the Saturnian day continues to elude us. ®