The Cassini spacecraft observed Saturn’s equinox in 2009, but it won’t be around for the next one in 2025
From a casual perspective, Saturn’s iconic rings look almost perfect. Made up of billions of particles of ice and rock, which F are thought to have come from comets, asteroids or shattered icy moons, they appear to seamlessly encircle the gas giant like a huge vinyl record. Since they were discovered by Galileo in 1610, the rings have become an immense source of fascination for astronomers, with so many discoveries having been made about them since. A lot of our knowledge of the rings came from the Voyager mission in the early 1980s, which gave us the first close-up images of the planet’s complex system.
As Voyager 1 got within 50 million kilometres (30 million miles) of Saturn on 6 October 1980, it allowed astronomers to see some unusual marks. Rather than venturing in the same direction as the rings, they appeared to cut across them, like rods radiating from the centre of a wheel. Scientists had never seen this before, and they were intrigued to discover what may have been causing them. Named ‘spokes’ they’ve caught the imagination of researchers ever since. “The spokes are fascinating because they were so unexpected when Voyager flew by – we expected pristine icy and maybe rocky pieces, but
