Popular Astronomy

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Saturn from Voyager 2

Image: NASA



Amazing fact!

Saturn is so light that if you could put it in an ocean big enough, it would actually float!

     Saturn might be the most amazing planet in the Solar System. Just look at those rings! No other planet has anything like them. They are made of ice and dirt, and probably formed when a comet got too close to Saturn and was ripped to shreds by its gravity. If you are lucky enough to have looked at Saturn through a telescope, you’ll know what I mean when I say it is a beautiful sight. If you need further convincing, just look at the pictures from the Cassini spacecraft at NASA’s website: http://saturn.jpl.nasa.gov/home/index.cfm
      There’s more to Saturn than just rings. Like Jupiter, it is a gas giant, which means that it is big – it’s the second largest planet in the Solar System, at 120,536 kilometres across. Because it is farther from the Sun than Jupiter (at a distance of 888 million kilometres) it is also colder, so there is not as much activity in its atmosphere. However, there are still large hurricanes and storms, though not as big or dramatic as the Great Red Spot.
      So far, we have discovered 62 moons around Saturn (I say so far as Cassini keeps finding new, tiny moons). Titan is the largest of Saturn’s moons. It has a thick, orange atmosphere that we can only see through with radar and infrared. In 2005, the European space probe Huygens landed on Titan, and photographed the surface. Everything was bathed in an orange colour, and pebbles of ice were scattered across the ground. Huygens had landed in an area that is sometimes flooded, not with ice, but with liquid methane! Cassini has since found seas and rivers of methane and dunes not of sand but of ice crystals. Liquid methane can exist because it is cold enough on Titan at –179 degrees Celsius. It makes me feel cold just thinking about it!
      Enceladus (pronounced En-sell-ah-dus) is also an interesting moon. Cassini has flown through fountains of water vapour that are jetting out from cracks at its icy south pole, and this might mean there is liquid water beneath the surface, a bit like on Jupiter’s moon Europa.
      Other interesting moons include Iapetus, which has one dark side and one light side as well as a wall of mountains that runs around its equator, and Mimas, which sports a huge crater from an impact that nearly smashed the poor little moon apart. The crater now makes it look like the Death Star from Star Wars!



Titan from Voyager 2Titan from Huygens lander


Before Cassini visited Titan we could only see its thick orange atmosphere (left), but with infrared 'eyes' we could see right down to the surface (middle)! The Huygens probe landed on surface and showed us what it was really like on Titan (right). Images: NASA/JPL/Space Science Institute/ESA.