Saturn’s moons

Saturn has 62 moons. Perhaps more, but as of March 2011 astronomers have confirmed the orbits of 62. I learned this fun fact while manning (or rather “womanning”) the Saturn booth at The North Carolina Museum of Natural Sciences’ Astronomy Day.

Today the museum brimmed with expert and amateur astronomy buffs, ranging in age from six to eighty. I fall into none of these categories (not expert, amateur, six nor eighty). Thankfully I worked alongside an expert, who quickly briefed me on Saturn, its rings and its moons.

Here’s an excerpt from the beginning of the day, before my briefing:

    Museum visitor [pointing at photo in front of me]: “What’s that?”
    Sarah [shifting nervously]: “Saturn? No, wait, that’s one of Saturn’s moons. The big one. What’s the big one called?”

Titan. The big one is Titan. With a diameter 50 % larger than that of Earth’s moon, Titan is Saturn’s largest. Some astronomers consider Titan a planet trapped in Saturn’s orbit, as it’s one of few celestial bodies with a surface atmosphere, mountains and lakes. Saturn, a gas giant with no solid surface, has none of these features. Seems to me like Saturn should be orbiting Titan.*

*Disclaimer: As I am not an astronomist perhaps this is crazy talk.

Titan’s northern polar region boasts the majority of the lakes, the largest of which trumps the size of Lake Superior. The key difference between Titan’s lakes and Earth’s lakes is this: Titan’s lakes are not filled with water; they are filled with liquid methane.

Methane is a gas here on Earth, because Earth’s atmosphere is relatively hot. Titan’s atmosphere, namely methane and nitrogen, is 95 Kelvin. 95 Kelvin translates to –178 ˚Celsius and –289 ˚Fahrenheit. That’s cold.

Titan: Saturn's largest moon.

Here’s an excerpt from the end of the day:

    Museum visitor [pointing at photo in front of me]: “What’s that?”
    Sarah [smiling proudly]: “That’s Titan, Saturn’s largest moon. The atmosphere on Titan consists of methane and nitrogen and is almost 300 degrees below zero. Bring a parka and some mittens!”

Iapetus (pronounced YAH-peh-tus), the third largest of Saturn’s moons, has a topographic ridge that lies almost directly on top of its equator. It literally looks like someone made a Play-doh snake and plopped it down to define Iapetus’s equator.

Hyperion is my favorite moon because it looks like a sponge. A museum visitor likened it to a pumice stone, which is probably more accurate. Hyperion has very low density compared to the other moons, and as a result has weak gravity and is quite porous. It’s non-spherical and would be tough to pick out in a line-up of asteroids.

Hyperion: Saturn's coolest moon.

Dione (pronounced die-uh-nee) is another of Titan’s moons, one of the densest. The surface of Dione is chock full of craters. It looks very much like our moon.

Enceladus (which you pronounce like the Mexican food, but without the “h”) has active eruptions! This is quite rare in outer space. This moon is Saturn’s sixth largest and Cassini (see below) captured Enceladus at a distance of 15 miles, close enough to see crevices, fractures and grooves. For reference, this photo was taken at 2,000 miles.

The photos of Saturn’s moons are courtesy of the Cassini spacecraft. NASA launched Cassini in 1997 and, after seven long years, the unmanned spacecraft reached Saturn. Cassini has been orbiting Saturn since, and will continue to orbit Saturn, photographing the gas giant, its rings and its moons until 2017, when the mission ends.

I was told that once 2017 rolls around, Cassini will take close-up photographs of Saturn’s rings as the spacecraft “dies.” The specifics here are lost upon me.

Not lost upon me, though, is that we need high-definition photos of Saturn’s rings. Saturn has at least 10,000 rings and we need to define that mess of icy dust. By our best estimates, the ring system spans 1 kilometer thick by 280,000 kilometers wide. For the anti-metric system folks, that’s less than a mile thick by 174,000 miles wide.

You’d have to circle the Earth seven times to traverse Saturn’s ring system. That’s a lot of ring.

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One response to “Saturn’s moons

  1. How do you pronounce all of the moons?

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