The Mysteries of Saturn, Both Solved and Unsolved

September 16, 2015 | Sarah Tse

the planet Saturn, surrounded by rings
Photo credit: NASA

There’s so much more to Saturn than its rings.

The sixth planet from the sun has been observed in the night sky since ancient civilizations. Since then, stargazers and astronomers have come across a variety of strange phenomena that have collected even stranger explanations. Read on to see what we’ve learned about Saturn in all that time, and what we have yet to figure out.

Saturn’s most defining characteristic, its dramatic ring structure, was first spotted by Galileo in 1610. He couldn’t make out their exact appearance and thought that Saturn might in fact be a three-bodied system, with two smaller objects that came in and out of view throughout the year. But the Vatican, eager for another opportunity to disprove the Italian scientist, declared instead that these appendages were in fact a relic of Jesus’s ascent into the heavens--namely, his foreskin. Luckily, about half a century later Dutch astronomer Christiaan Huygens used a more powerful telescope and identified the “foreskin” as a ring. And of course, we now know the bands are made of icy particles ranging in size from dust motes to mountains. But it was an interesting theory.

Determining the length of a planet’s day seems straightforward--all you have to do is measure how long it takes to make one rotation on its axis. But Saturn proved to be a bit more challenging. First of all, its gaseous surface lacks any landmarks that scientists can could as time-posts. The Cassini probe tried measuring the planet’s radio radiation, but got different results each time it went back for another look. Another method, of measuring the rotation of the planet’s magnetic field in relation to its axis, failed because Saturn’s magnetic field lines up perfectly with its axis. Finally, a team of astronomers at Tel Aviv University tried a different, more theoretical approach. They played with a series of calculations using different values to represent Saturn’s interior variations, based on the well-known data collected for its gravitational field. They were able to narrow down Saturn’s rotation period to 10 hours and 33 minutes.

When Saturn’s F-ring was first discovered in 1979 by NASA’s Pioneer 11 probe, astronomers were not sure how to explain the icy band’s constantly shifting behavior and braid-like appearance. The F-ring is shepherded by the moons Prometheus and Pandora, which dip in and out and herd its icy particles into a 60 mile-wide band. Over the next 25 years, additional surveys of the planet showed that the F-ring looked completely different at certain points, losing some of its brightest clumps. It turns out Prometheus plays with the ring materials on a 17 year cycle, sometimes pulling them out to form tiny moonlets and sometimes causing them to blend in with the rest of the ring.

Such close interaction between the moons and the band didn’t make sense, because the moons should have dissolved into the band when they first formed. But scientists very recently devised new models revealing that the two moons could have formed from a collision if they were sufficiently dense, and the residual debris would have left behind the F-ring.

Another of its rings, called the Phoebe ring, wasn’t discovered until 2009. It’s more of a cloud than the other rings, as it spans an area nearly 7,000 times larger than Saturn itself. Astronomers were alerted to its existence by the strange bipolar coloring of Iapetus, a Saturnian moon with a coating of dark particles on the side facing the Phoebe ring. These particles absorb light, rather than reflecting it, so the ring could only be detected using an infrared telescope that sensed their heat. Phoebe, the moon that gave the ring its name, is made entirely of these dark particles.

The ring’s existence is a bit of an anomaly, because the ring extends so far from Saturn that its particles should collapse into tiny moons. Astronomers believe the ring’s materials were released from Saturn’s moon Phoebe during small meteoroid impacts, since both the moon and the ring orbit in the opposite direction from their Saturnian brethren.

Saturn has some extremely strange storms rolling through its atmosphere. Scientists have observed a hexagonal storm spinning above its north pole for almost 40 years. Each side of the hexagon is nearly 7,500 miles long, and reaches 60 miles down into the atmosphere. Since it was first spotted, it has remained remarkably consistent in shape and location. Astronomers have discovered that smaller storms lower on the planet are ripped in half and dragged up thte pole, but they still aren’t sure what maintains the storm’s perfectly geometric shape.

Meanwhile, the planet’s opposite pole hosts an eerie eye-shaped storm. Like hurricanes on earth, the eye itself is clear of clouds, but the surrounding clouds extend up to 5 times taller than hurricane clouds on Earth. How the storm stays fixed directly above the south pole remains a conundrum.

If you liked these facts, read about the giant planet that used to orbit our solar system

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