A Long Seasonal Shift
Four years after the equinox on Titan, Saturn's largest moon, signs of the seasonal shift have finally arrived. This spring, an ice cloud took shape over Titan's south pole. Meanwhile, the ice cloud over the north pole has been receding. The alternation of ice clouds signals a reversal in patterns of global air circulation on Titan that scientists had predicted with the passing of seasons.
The official transition from winter to spring at Titan's north pole occurred in August 2009. But because each season lasts about seven and a half Earth years, researchers still didn't know exactly when this reversal would happen or how long it would take. That answer came partially in July 2012, when NASA's Cassini spacecraft detected a high-altitude “haze hood” and a swirling polar vortex at the south pole—signs that the south was cooling down.
KIMBRA CUTLIP is a freelance writer and former assistant editor for Weatherwise.