Humid Skies 
Springtime in much of the United States means muggy days and steamy nights, as moisture moves in from the Gulf of Mexico, creating high levels of humidity.
An astronomer at the University of Texas is looking at how the humidity varies on another world: Titan, the largest moon of Saturn.
Titan’s atmosphere is similar to Earth’s. It’s thick, it’s made mainly of nitrogen, and it supports a weather cycle that includes clouds and rainfall. But Titan is hundreds of degrees colder than Earth, so the clouds and rainfall are made not of water, but of liquid methane.
The Cassini spacecraft has made dozens of close passes by Titan, providing many details about its atmosphere. But it watches Titan for only a few hours or days at a time, with long gaps between passes.
Texas astronomer Laurence Trafton is using observations from ground-based telescopes to fill in the gaps. In particular, he’s measuring the amount of methane in the atmosphere at different points on Titan. Since methane fills the same role as water does here on Earth, measuring the amount in the atmosphere reveals the humidity — how “muggy” Titan’s air gets.
Monitoring Titan will reveal how methane varies by location and by season. And comparing the methane humidity in the summer and winter hemispheres will provide a better picture of Titan’s climate, and reveal where the methane is coming from — helping scientists predict the weather on this cold, humid world.
More about Titan tomorrow.
Script by Damond Benningfield, Copyright 2012