The Lunar-cy of Moons

Mini-Moon fact-lets:

  • Moon rocks are magnetised which is weird as the Moon has no magnetic field itself, scientists are still confused as to how this happened as a ‘close call’ with Earth would have ripped the moon apart.
  • The Moon’s mean density is 3.34 times that of water whereas Earth’s is 5.5 suggesting that large areas of the Moon’s interior are cavernous.
  • The lunar surface is littered with odd looking structures ranging from tiny canister-like shape to the “Shard” which is a tower that could be at least 1.6km tall.
  • It’s estimated that there’s 181,437kg of manmade materials littering the Moon’s surface including space probes, lunar rovers and astronaut poo containers.


“That’s no moon, that’s a space station.” For anyone who has watched Star Wars: A New Hope, Alec Guinness’ famous line conveys a sense of dread from the realisation that the empire had constructed an orbital machine of awesome destructive power. Perhaps it’s just my nostalgia for one of my favourite childhood movies, but the Death Star represents a major piece of cinematic history. Its design – a mere figment of someone’s imagination – has, undoubtedly, withstood the test of time. Since the release of the A New Hope, telescope technology has moved on, satellites have been launched and we have begun to map the planetary bodies of the solar system in greater detail. So imagine the surprise of stargazers when they found several moons that looked remarkably similar to the iconic space station.

Let’s begin with Mimas – its size calculated at 10% of that of our moon – making it one of Saturn’s smaller satellites. When viewing it at just the right angle, the massive crater on its northern hemisphere resembles the laser dish of the Death Star. It’s quite the coincidence that this moon, located 1.27 billion km from earth, looks just like Grand Moff Tarkin’s dream project. Mimas has another other trick up its sleeve; when viewed in the infrared spectrum, it has an image of Pac-man eating a dot on its surface. It’s still a mystery to astronomers and astrophysicists why the thermal pattern on its surface looks so weird, although it could be due to the rock composition of the moon’s mantle or some surface texturing effect.

This isn’t the only fantastic little moon in our solar system; Phobos, Mars’ largest moon, also resembles the Death Star. Measuring at just 22km in diameter, Phobos was previously hit by an asteroid or comet which produced the 9km wide Stickney crater. Recent simulations have shown that to create a crater this size, it would require the impact of an object with a 250m diameter travelling at 6km/s.

Death star moons aren’t the only surprise small satellites existing in the solar system. Io, the fourth largest moon of Jupiter, is a fiery hell of intense radiation and constant volcanic eruptions – spitting out 100 times more lava that all of Earth’s volcanoes. However, Io is cold enough to be covered in layers of sulphur dioxide frost. All this activity can result in massive plumes of gas and dust erupting up to 500km into space.

Now to the oddball moons of the solar system. Saturn’s Pan and Atlas both have a centre bulge and disc around their equators, giving them the resemblance of flying saucers. The pair are truly tiny; Atlas has a diameter of 18 km from pole to pole, compared to 40km across the disc. It is thought that their rotund shape is caused by a combination of their rapid rotation and proximity to Saturn’s rings, causing them to gather icy material at their equators.

Finally we have Titan, Saturn’s largest moon, which is perhaps the strangest of all. When images first returned from the Huygens probe in 2005, scientists peered through the haze of its thick nitrogen atmosphere to see a surface that looked eerily like Earth. It has lakes, hills, caves, plains and desert dunes just like the rock we call home. Don’t be fooled by the similarity though, Titan’s temperatures reach a very chilly -1800C. The lakes and rivers are of great scientific interest; consisting of liquid hydrocarbons such as methane, ethane and propane, which may provide a food source for alien life yet to be discovered.

When you know worlds like these exist, it’s hard to be bored when looking up at the night sky. Indeed, maybe if you look a little closer you’ll find something fantastic and, following the American election results, I bet there would be no lack of volunteers wanting to go and visit these extraordinary moons.


Sam McMaster

Science Editor


(Image courtesy of NASA/JPL/Goddard/SWRI/SSI)

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