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Saturn's Moons

Saturn has 62 known moons.

Titan: Smog World

Surrounded by a thick atmosphere that's topped by orange smog, and with a landscape that in some ways resembles Earth, Titan is one of the solar system's most intriguing moons.

Titan's frigid atmosphere is about 60 percent denser than Earth's at the surface, and clouds float across the sky. A global haze of organic molecules tops the atmosphere, so it was almost impossible to study the surface until the Cassini spacecraft, which carries instruments that can peer through the haze, arrived at Saturn in 2004.

  Titan Enceladus Iapetus Mimas
Discovery 1655, Christiaan Huygens 1789, William Herschel 1671, Jean Dominique Cassini 1789, William Herschel
Diameter 3,200 miles
5,150 km
310 miles
500 km
893 miles
1,436 km
2,985 miles
4,806 km
Distance from Saturn 745,000 miles
1.2 million km
147,812 miles
238,020 km
2.2 million miles
3.6 million km
115,210 miles
185,520 km
Orbital Period 16 days 1.4 days 79.3 days 22 hours, 37 minutes

Scientists had expected to find large seas or oceans of liquid methane, but Cassini found that there may be only a few small bodies of liquid. The Huygens probe, which parachuted through Titan's atmosphere in early 2005, photographed a landscape that, in some ways, is similar to Earth's, with possible drainage channels carved into hillsides. Huygens' instruments also found a thin layer of ice coating the surface at its landing site.

Titan's surface consists of rock and ices. Volcanoes may belch methane into the atmosphere, contributing to the moon's smog layer.

Tracking Titan's Temperature

As the Huygens probe parachuted through the atmosphere of Saturn's moon Titan in January 2005, it took the first direct measurements of temperatures, wind speeds, and the atmosphere's composition. Yet it sampled only one small region on one day. To fully understand Titan's complex atmosphere, scientists must study the entire moon, and repeat their observations to see how it changes over time.

In support of that goal, McDonald Observatory astronomer Laurence Trafton and his colleagues monitored Titan around the time of the Huygens landing from the Infrared Telescope Facility atop Hawaii's Mauna Kea. Their observations looked at the abundance of an organic molecule that could help yield clues to the atmosphere of the early Earth, which Titan's present-day atmosphere may resemble. The observations also can serve as a comparison to those made by Huygens, helping scientists calibrate the probe's discoveries.

Trafton was using a Texas-built spectrograph, TEXES, to study the molecule cyanoacetylene. This organic molecule is of particular interest because it contains nitrogen, which is one of the ingredients of amino acids, which are some of the "building blocks" of life. The early Earth probably contained similar molecules, so studying them on Titan could yield new information about the atmospheric conditions that led to life on Earth. The molecule also provides a look at temperatures in Titan's upper atmosphere across the entire moon. The Texas rese