Time is running out for Cassini's mission. After more than a decade exploring Saturn and its moons, the spacecraft is in its last few months of operations before a planned suicidal plunge in September 2017. The mission is low on fuel, and there's a small risk that it could collide with an icy moon.
One of the special things about being at Saturn for so long is following the slow change of the seasons. It takes Saturn 29 years to orbit the sun. Cassini has now been at Saturn for almost a half-year, or 14.5 Earth years. Different parts of the planet are better illuminated as the gas giant swings around the sun, showing the nature of the poles and their changing seasons.
It is the poles that come under scrutiny in a new paper in the journal Icarus, which compares the north and south polar vortexes on Saturn. Massive storms rage around Saturn's poles, similar to Jupiter's Great Red Spot - but not quite as powerful.
"The north pole showed a lot clearer details, while the south pole generally looked fuzzy," Kunio Sayanagi, an assistant professor at Virginia's Hampton University who led the research, said in an e-mail.
Sayanagi attributed differences to seasonal variation at the poles.
"The north polar data we analyzed in the paper is from late 2012, which is basically early spring, while in 2007 the south pole was in late fall," he said. "Between the equinoxes in 1995 and 2009, the north pole didn't get any sunlight because it was in the long winter polar night. Opposite is true for the south pole - it continuously baked in sunlight during that time."