Just once every 15 years, Saturn approaches its equinox —
when the sun passes through the plane of the planet's rings.
NASA's Cassini
spacecraft has captured rare scenes of moons
eclipsing each other and casting long shadows against the rings during the
approach to this equinox.
One year on Saturn is equal to 29.5 Earth years. Twice
during that period Saturn aligns with the sun so that the flat plane of the
planet's titled rings also intersects the sun. During these equinox alignments,
the angle of the sun illuminates the Saturnian system in a unique way and
creates rare shadow patterns.
These patterns recently revealed enormous mile-high vertical
waves on the edges of a gap in Saturn's outer ring that had never been spotted
before.
The exact date of the approaching equinox is Aug. 11. Over
the next few months, scientists hope the special
views lead to even more new discoveries about Saturn's rings.
"It has been a scientist's delight to watch this almost
wafer-thin collection of icy debris, that we have come to know so well, change
in character and spring into the third dimension," said Carolyn Porco,
leader of the Cassini Imaging Team.
Launched in October 1997, the Cassini spacecraft has been
orbiting Saturn since 2004. Among the probe's many discoveries, it revealed
three previously unknown moons, Methone, Pallene and Polydeuces, to add to
Saturn's tally of 61. Cassini is currently slated to run until next year, but
if funding is approved the mission could be extended
until 2017.
Correction: This article has been corrected to reflect the correct year Cassini went into orbit around Saturn: 2004.
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