Delivering more than just pretty pictures, the Cassini spacecraft returned an impressive collection of photographic firsts of Saturn and its environs this year. They include views of an improbable hexagonal feature, containing a huge system of swirling clouds, at the planet’s north pole, as well as never-before-seen views of the top and bottom of Saturn’s rings.
Voyager provided the first glimpses of the hexagonal cloud structure some 27 Earth years (about one Saturn year) ago. This time, Cassini, which entered orbit around Saturn in June 2004, was able to capture the entire object. The origin of the hexagon—so large that two Earths could be lined up across its diameter—is a mystery. “Clouds circulate around the feature like cars on a racetrack,” says Kevin Baines, a planetary scientist at NASA’s Jet Propulsion Laboratory. Studying this formation may give us a better idea of how fast Saturn rotates on its axis, Baines says, a measurement that is difficult to make because of the planet’s fast winds.
The latest images of Saturn’s rings, which show propeller-shaped clumps and moonlets shattered by an ancient impact, are also giving astronomers a lot to think about. Carolyn Porco, leader of the Cassini imaging team, says the ring pictures may even help us figure out how Earth formed: “If we understand how icy particles in the outer solar system behave, then we can refine our understanding of how the early solar system formed from that same material.”
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