Saturn’s UFO-Shaped Moons: Pan and Atlas

Two odd ufo shaped moons of Saturn are worth seeing on our tour of true strange stuff in the universe. Two of them, Pan and Atlas, as seen by NASA’s Cassini spacecraft, are each about 12 miles (20 kilometers) across, have a roughly flying saucer shape. How could these shapes have formed naturally?

UFO? Pan is Saturn's most inner moon, as seen in this illustration. It orbits within the Encke Gap in the planet's A ring

Wikipedia calls Pan “walnut-shaped” but that’s no walnut shape we’ve ever seen. It is a flying saucer shape, clearly.

It is a small, walnut-shaped moon approximately 35 kilometres across and 23 km wide that orbits within the Encke Gap in Saturn’s A Ring.  … The moon was named on 16 September 1991, after the mythological Pan, who was (among other things) the god of shepherds. This is a reference to Pan’s role as a shepherd moon. (Source)

An article in the Daily Mail said that each moon started with a massive core that was a leftover from the original collisions that caused the rings.Their unique shape may be due to the fact that spinning will cause the edges of a structure to flatten out. Accretion discs are seen at all scales in the universe from planetary rings to galaxies.

‘Our computer simulations show that the ridges must have accreted rapidly when Saturn’s rings were thin, forming small accretion disks around the equators of Pan and Atlas,’ said Sebastien Charnoz, from the University Paris-Diderot in France. (Source)

The following images are different versions of data collected by NASA’s Cassini spacecraft, showing differing amounts of shadows and details of Pan, the inner most named moon of Saturn.


These two images from NASA’s Cassini spacecraft show how the spacecraft’s perspective changed as it passed within 15,300 miles (24,600 kilometers) of Saturn’s moon Pan on March 7, 2017. This was Cassini’s closest-ever encounter with Pan, improving the level of detail seen on the little moon by a factor of eight over previous observations.

No one is claiming that the moons Pan and Atlas are actual giant flying saucers. This is just a common shape due to the way gravity works with spinning objects.

Here’s an image of the moon Atlas where you can see a similar flying saucer shape.

Atlas was discovered by Richard Terrile in 1980 (some time before November 12) from Voyager photos and was designated S/1980 S 28. In 1983 it was officially named after Atlas of Greek mythology, because it “holds the rings on its shoulders” like the Titan Atlas held the sky up above the Earth. (Source)

Wouldn’t it wild to walk around on the lip of these ufo shaped moons in a space suit? Would you just float away? Both of these moons have a low density and an article in Science Mag when these photos were first released said “the ridge [of Pan] can maintain its steepness only because the moon’s gravity is so low.”

Pan is about 12 miles across, but is not round, so you might be able to jump or just push away from it depending on where you were standing. For perspective, you could stand on Demios, a moon of Mars which is only about 8 miles across on average according to one source.

Even Deimos (the smaller of Mars’ two moons) has an escape velocity of only about 12.5 mph, so with a good running start you could literally jump into space.  I figure 12.5 mph is about the fastest that most people can muster in a pinch, so Deimos is about the smallest object that can hold people down, at about 8 miles across (8 miles on average, due to lumpiness). (Source)

It is not in our earthly experience to be walking around while feeling gravity changing based on our location, but that would be the experience on small irregular shaped moons. Interesting to think about.

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1 comment

marjoriekaye March 21, 2011 at 9:40 pm

Look like baby Saturns

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