Equinox at Saturn

Since 2004, Cassini’s Composite Infrared Spectrometer (CIRS), has collected data on the thermal behavior of the main rings of Saturn.

Saturn experiences Equinox as Earth does every spring and fall.



But seasons on Saturn are much longer.

It takes around 30 years for this gas giant to complete a full orbit around the sun...

so an Equinox occurs roughlyevery 15 Earth years.

Because Saturn’s rotational axis is tiled with respect to its orbital plane,

from the sun, Saturn appears to show its rings at different angles at different points in its orbit.

For nearly half of Saturn’s orbit, the sun shines on the south side of the rings.

For the other half, it shines on the north side.

And every time the rings cross Saturn’s orbital plane, Equinox happens.

As less and less solar energy heats the rings, they cool down.

From 1994 to 2009 the sun illuminated the south side of the rings.

Cassini’s Composite Infrared Spectrometer had a unique view of the cooling of the rings.

Animation shows sun angle changing from December 2004 to August 2009 and shows temperature changes in the rings.

Equinox

The temperature of the side of the rings hidden from the sun changes, too.

Animation shows sun angle changing from December 2004 to August 2009 and shows temperature changes in the rings.

Equinox

NASA, Jet Propulsion Laboratory, California Institute of Technology