Iapetus, the Dinosaur Moon

Iapetus is a moon of Saturn with a funny name and a funny geological feature. I always think of it as the "dinosaur moon", because it has a distinct ridge feature on its surface that reminds me of the back of a dinosaur. Orbiting at 2.2 million miles from Saturn's surface, it's farther away from Saturn than Titan is. The surface of Iapetus was imaged by the Cassini mission in 2004, and the images revealed the equatorial ridge, a 6 mile high mountain range. It's a bit unclear how this band of mountains ended up on Iapetus. One theory is that a long time ago, Iapetus had a ring similar to Saturn's ring. As the moon evolved, the ring began to collapse onto the surface, and this ridge is where all the material collected. A second idea is that the ridge formed during a time when Iapetus was spinning on its axis much faster than it does today. Bodies in space, such as the Sun and the Earth, spin on their axis. Because of this, they bulge just a little bit in the middle. So Earth and the Sun are not perfect spheres, but rather balls that are slightly wider at the center. If Iapetus was spinning really fast some time in the past, this ridge might be the result of the moon bulging in in the middle. Astronomers will have to take a closer look at the composition and orbital properties of this moon before they can determine exactly how the ridge formed.

Image Credit: NASA/JPL/Cassini

Saturn's Rings and Enceladus

We all know Saturn as the big outer planet with the rings. Why does Saturn have such beautiful ring structure? Astronomers aren't entirely sure, but they must have formed back when Saturn was just an infant planet. Astronomers can, however, explain the existence of Saturn's outermost ring, the E ring. Where did this ring come from? The culprit is Saturn's Moon Enceladus!

Above is a recent image taken by the Cassini spacecraft which is currently orbiting Saturn and its moons. As you can see, there appears to be some material erupting from the surface of the moon, and indeed there is! Enceladus experiences what we call cryovolcanism, which means that it has volcanoes which spew water and ammonia when they erupt instead of hot rocky lava. These eruptions are so intense that the material actually leaves the planet and travels into outer space! Since Saturn's rings are so close to Enceladus, the water and other molecules get caught up in Saturn's gravitational field and form the outermost ring. This ring is technically unstable, which means the material will stay for a short time, but then be lost forever into space. That's no big deal though, because Enceladus is continually erupting and adding new material to the E ring.
Image credit: NASA/JPL-Caltech/Space Science Institute

Ring Around The.... Planets?

Open a new tab in your internet browser (yes, right now). Go to Google and pull up an image of Saturn (I don't care that you know what it looks like, just do it). Remember that picture, and look up a picture of Jupiter, Uranus and Neptune as well. Now if I start singing the song "One of these things is not like the other…" what would your answer be?...... The answer I was going for was Saturn! What's so different about Saturn? Well as you saw from the picture, Saturn has a beautiful ring structure and the other planets don’t….. Wrong! Believe it or not, all of the gas giant planets have rings! (Now if you didn't actually go to Google before, I bet you are now just to see if you can find a wiki page on ringed planets to see if I'm right.) 

 

Saturn's ring structure is very bright and prominent because it is thick and made mostly of ice which reflects light. The rings around Jupiter, Uranus, and Neptune are much thinner and are mostly made of rocks. Pictures of each planets rings are shown above. There's a big black spot over Neptune because Neptune is so bright compared to its rings that the planet's light needed to be blocked out so the rings were visible . Now when someone refers to Saturn as the ringed planet you can say "actually, all the gas giants have rings… but I know which one you mean."

Image credits: NASA/Voyager/J. Rayner/NSFCAM/IRTF

Week of Moons: Titan

Silly me forgot to post the final week of moons update on Friday, as blogspot was down Friday morning. So here is the final Week of Moons post about Titan. It ties in nicely with today's post about Cassini-Huygens.

 

Titan, the largest moon of Saturn, is one of my favorites. Why? Well take a look at the infrared picture above (bottom left) and tell me what it looks like….. Earth! Titan is very much like Earth was way back when it was just a baby, about 4 billion years ago.  It's about half the size of Earth and has a dense nitrogen atmosphere. It's the only moon in our solar system that has a thick atmosphere, and the only object to have flowing liquid and lakes on it! Unfortunately these lakes are not water lakes, but methane lakes (too toxic for humans to swim in!) There are also volcanoes which spew out  water and methane (cryovolcanism), suggesting that there might be a layer of liquid water underneath Titan's crust! Astronomers think that Titan may be the best place to look for life in our solar system, as it is so similar to Earth. The Huygens Lander discovered in 2005 that the surface of Titan contains carbon compounds, further supporting the idea of possible life! Now we don't expect to find an alien civilization walking around, but we may find bacteria or other organisms who've adapted to the conditions and are living either on the surface or in the methane lakes. NASA and ESA are planning robotic missions to land on and study Titan, but no official announcements on when this will occur have been made. I guess we will just have to wait and see!

Image Credit: NASA/JPL/Cassini-Huygens

Cassini-Huygens Mission

The Cassini Huygens mission launched in 1997 with the purpose of studying Saturn and it's Earth like moon Titan. The spacecraft reached Saturn in 2004 where Cassini entered orbit around Saturn. Huygens landed on Titan about one year later. If you've ever looked at Saturn through a telescope it's absolutely spectacular. On a good night you can clearly see the rings and even some of the moons! It almost looks like someone put a scrapbooking sticker of Saturn at the end of the telescope, it's that clear. Cassini giving us an up close and personal look at the planets and it's moons;the image above being one of them. A 2 minute video of images Cassini sent back to Earth is the feature of today's Astronomy Picture of the Day. Check it out here

Image credit:

NASA/JPL/Space Science Institute