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wtf_nature
Ring-a-Ring-a-Rhea
It used to be thought that Saturn was the only planet with rings. And very spectacular rings they are, too, with such amazing details as braids, arcs, shepherd moons, spokes and kilometre-high ripples. The latter appear to date from 1984, when something happened - possibly a belt of extra-high-velocity wind on Saturn itself - to tilt the inner sections of the ring slightly. The outermost ring even appears to orbit backwards.
But in 1977 three astronomers waiting to watch a star vanish behind Uranus discovered that it, too, had rings (or possibly, just rediscovered something Herschel himself had reported in 1789 ). And two years later Voyager 1 discovered faint dust rings around Jupiter. By this point it was hardly going to be a surprise if Neptune had rings as well, but the planet still managed to baffle us with its outer ring divided into five stable arcs since named Fraternité , Egalite 1 and 2, Liberté, and Courage
It seems highly likely Earth has had rings in the past as well, after major impacts. And they would exacerbate climate damage, too, by cutting off sunlight to the winter hemisphere and reflecting extra light onto the summer side.
But even after all these discoveries, Saturn has managed to surprise us again, with the discovery that the large moon Rhea has its very own ring system. As the Cassini probe orbits Saturn it's been measuring the magnetosphere of the planet. All the moons cast deep plasma shadows, but Rhea also had three symmetrical dips either side - clear evidence that three rings of something were mopping up charged particles inside Rhea's gravitational influence.
And double checking photographs of the moon uncovered chains of ultraviolet-bright spots right around the equator - now suspected to be the result of ring debris finally falling in.
Sad to say, the rings seem to be too faint to show up directly on even the best Cassini photos, but Rhea's rings are still an astonishing discovery - the first stable rings of a moon. Although, given the history of the planetary rings, it's not impossible that we'll discover half-a-dozen more over the next few decades.
But in 1977 three astronomers waiting to watch a star vanish behind Uranus discovered that it, too, had rings (or possibly, just rediscovered something Herschel himself had reported in 1789 ). And two years later Voyager 1 discovered faint dust rings around Jupiter. By this point it was hardly going to be a surprise if Neptune had rings as well, but the planet still managed to baffle us with its outer ring divided into five stable arcs since named Fraternité , Egalite 1 and 2, Liberté, and Courage
It seems highly likely Earth has had rings in the past as well, after major impacts. And they would exacerbate climate damage, too, by cutting off sunlight to the winter hemisphere and reflecting extra light onto the summer side.
But even after all these discoveries, Saturn has managed to surprise us again, with the discovery that the large moon Rhea has its very own ring system. As the Cassini probe orbits Saturn it's been measuring the magnetosphere of the planet. All the moons cast deep plasma shadows, but Rhea also had three symmetrical dips either side - clear evidence that three rings of something were mopping up charged particles inside Rhea's gravitational influence.
And double checking photographs of the moon uncovered chains of ultraviolet-bright spots right around the equator - now suspected to be the result of ring debris finally falling in.
Sad to say, the rings seem to be too faint to show up directly on even the best Cassini photos, but Rhea's rings are still an astonishing discovery - the first stable rings of a moon. Although, given the history of the planetary rings, it's not impossible that we'll discover half-a-dozen more over the next few decades.