NASA is about to learn everything there is to know about Saturn’s seven main rings, as the 20-year Cassini spacecraft mission gears up for its emphatic final flourish.
Between now and next September, Cassini, one of NASA’s most successful planetary reconnaissance missions ever, will dive beneath Saturn’s rings dozens of times.
Passing through the unexplored region at the outer edge of the main rings before getting closer to its ‘home’, Cassini’s undulating final 10 months will attempt to directly sample ring particles and molecules of faint gases that are found close to the rings.
This all marks the final throes of the spacecraft which will, during its 20th year in space, ultimately embark on its mission-ending plunge into the planet’s atmosphere on 15 September, 2017.
Cassini’s initial ring-grazing dives will begin on 30 November, continuing into next April. From then, it will orbit Saturn from just 90,000km above the planet’s clouds, before a final series of dives far closer to the planet’s surface.
During the first two orbits, the spacecraft will pass directly through an extremely faint ring, created after tiny meteors struck the two small moons, Janus and Epimetheus. However, it’s after this that the fun begins.
Ring crossings in March and April will send the spacecraft through the dusty outer reaches of the F ring. This will reveal new information on the moons Pandora, Atlas, Pan and Daphnis.
Grazing the edges of the rings also will provide some of the closest ever studies of the outer portions of Saturn’s main rings (A, B and F).
The mission will continue investigating small-scale features in the A ring called “propellers”, which reveal the presence of unseen moonlets. Observing propellers at high resolution will likely reveal new details about their origin and structure.
In March, while coasting through Saturn’s shadow, Cassini will observe the rings backlit by the sun, in the hope of catching clouds of dust ejected by meteor impacts.
Then the six-month countdown begins. During its grand finale, Cassini will travel as far as 1,628km above the clouds as it dives repeatedly through the narrow gap between Saturn and its rings, before descending for one final, destructive time.