Scientists Observe Daily Clouds on Titan

Oct. 20, 2000 -- New evidence of daily clouds rising above Titan suggest this moon of Saturn may be more active and more like Earth than scientists thought.

“Titan’s clouds are quite bizarre,” says Caitlin Griffith, a planetary astrophysicist at Northern Arizona University. “They show up at the same altitude every day and are extremely sparse, covering less than a percent of Titan’s globe.”

Earth-Like

Titan, Saturn’s largest moon and the second-largest moon in the solar system, has long intrigued scientists for its Earth-like qualities. Like on Earth, its most abundant atmospheric gas is nitrogen. It shares a similar surface pressure with our planet. The large quantities of methane and no free oxygen on Titan also mimics conditions around Earth billions of years ago.

The recently observed daily clouds around Titan add to evidence that the moon could host oceans and even occasional rain showers. On Titan, rain and clouds are most likely made up of liquid methane, not water. Methane is a gas in Earth’s atmosphere, but on Titan, cold temperatures render it a liquid. Discovery of the daily occurrence of clouds on Titan follows a finding two years ago of a hurricane-sized cloud in Titan’s lower atmosphere.

Cold and Dim

Despite the similarities to Earth, Titan would still be highly exotic to a terrestrial visitor. Temperatures average at an inhospitable -290 F and its atmosphere is 10 times more massive than Earth’s. That heavy atmosphere would lend a sluggish appearance to Titan’s skies, says Griffith.

“Standing on the surface of Titan, we would see a very dimly lit world, as bright as Earth under a full moon,” says Griffith. “Below the orange sky, the Sun would appear as a diffuse light source through Titan’s high smog.”

Different Weather Drive

Another important distinction between the planets is Titan’s greater distance from the sun — Titan is seven times farther from the sun and receives about 100 times less solar energy than the Earth. On Earth, solar energy drives weather. Griffith and her colleagues propose that, instead of solar energy, energy released when gas condenses to form clouds may be the main engine behind Titan’s weather.