There is a giant robot circling planet Saturn right now. And this robot is finding weird, amazing things: rainstorms of liquid diamonds, hurricanes bigger than the Earth, ice volcanoes…
But before we get to all that, I should back up a bit and give just a little background on Saturn so you will fully appreciate these new discoveries. Saturn is the sixth planet from the Sun, the farthest planet that can be easily seen without a telescope.
We have always known that Saturn was unusual. Actually, all of the planets were a little unusual to ancient star-gazers. They studied the night sky and saw that almost all the bright dots in the sky moved at the same speed and direction. But they also noticed that five bright dots in the sky moved differently than the stars and constellations. They called these five dots planets (which means wanderer): Mercury, Venus, Mars, Jupiter and Saturn wander among the constellations of the night sky.
More than 500 years ago, in the year 1610, Mr. Galileo found that Saturn was really weird. He was the first person to point a telescope at Saturn and he saw the most incredible sight; Saturn had ears! His drawings looked a bit like Mickey Mouse, with a big circle in the middle and ears poking out on the right and left side.
Another astronomer, Chris Huygens, using a better telescope, found that the “ear” Galileo saw were actually a ring around the planet, just like one you might wear on your finger. Then a guy named Gio Cassini used an even better telescope and could see that the ring was actually multiple rings (at least three) with clear separations between them.
Over the years, we have continued to learn just how weird Saturn is. Saturn has at least 62 moons and dozens of rings. It is the second largest planet, called a “gas giant” which means that it has no rocky surface, it’s all air. Even though it’s huge (760 times bigger than Earth), the gas is really light. If you could put Saturn in a big enough bucket of water, it would float!
Although it is so big, it spins really fast; a day on Saturn is only about 10 hours long. Gas spinning that fast causes tremendously violent storms. Hurricanes larger than whole the Earth rage across Saturn all the time.
Saturn’s super moon, Titan, is bigger than planet Mercury and has clouds, lakes, rivers and oceans.
By 1990 we had learned a whole lot about Saturn using Earth based instruments (and two very brief flyby missions). But there is just so much you can do from about 1 billion miles away. To learn more, we needed to get up close and personal for an extended time.
In 1997 we launched robot spaceship to do just that. It was named in honor of Mr. Cassini, and carried a smaller robot onboard named after Huygens. Cassini/Huygens was the biggest spaceship NASA had ever built, over 6 tons, big as a school bus. After a six year journey Cassini/Huygens arrived at Saturn and started sending back jaw-dropping details about our sixth planet.
In the next post, I will share some of the secrets of Saturn uncovered by Cassini/Huygens. Be prepared to be amazed!
Saturn’s rings disappear every few years! It happened in 1612, completely shocking Galileo. Then to his surprise, the next year they reappeared.
To understand why, you can do a simple experiment. Find a round disc in your home (a quarter, CD, frisbee…) and hold it out at arms length so it looks like a circle. Now tilt it so all you can see is the edge.
Saturns rings are like the disc in your hand. Saturns rings are very wide, but only 30 feet thick. As seen from Earth, Saturns rings wobble, and about every 7 years they are edge on, and basically invisible to us. Then they wobble some more and reappear.