Watching the seasons turn on Saturn


NASA’s Cassini spacecraft is currently observing the solstice on Saturn.


An enhanced-colour animation showing seasonal changes in Saturn’s north polar region between 2013 (left) and 2017 (right).
An enhanced-colour animation showing seasonal changes in Saturn’s north polar region between 2013 (left) and 2017 (right). Then colour change is believed to be caused by smog particles produced by increasing solar radiation shining on the polar region.
NASA / JPL-Caltech / SSI

While solstices happen on Earth every six months, Saturn’s 29-year orbit around the Sun makes them much rarer on the ringed gas giant. This time, NASA’s Cassini spacecraft will be in position to witness the event.

The solstice marks the shortest day of winter in Saturn’s southern hemisphere, while the planet’s northern hemisphere undergoes its longest day.

Cassini’s aptly named Solstice Mission will be the spacecraft’s second extended mission, and has been specifically designed to ensure the solstice and subsequent seasonal changes in Saturn’s system could be observed.

Saturn was first observed by Cassini in 2004 as part of an initial four-year mission to study the planet’s moons and rings.

Then, from 2008 to 2010, Cassini conducted its first extended mission, dubbed the Equinox Mission. As sunlight struck the planet edge-on, Cassini was there to watch new ring structures be revealed.

Beginning in 2010, Cassini’s most recent Solstice Mission has allowed scientists to witness, for the first time, an entire season on Saturn.

From April to September this year, Cassini will dive down between the planet and its icy rings in the hope of gaining new understanding of the planet’s interior and the origins of its rings. The mission will come to a crescendo on 15 September, when Cassini will take a final plunge into the planet’s atmosphere.

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