Category Archives: Saturn
Saturn’s “yin-yang” moon Iapetus (pronounced eye-AH-pe-tus) is seen in this image, a color composite made from raw images acquired by Cassini’s narrow-angle camera on March 11, 2017.
The color difference on Iapetus is due to a fine coating of dark material that falls onto its leading hemisphere, sent its way by the distant moon Phoebe traveling within the recently-discovered giant diffuse ring. This dark coating of dust causes that half of Iapetus’ surface to warm up ever-so-slightly-more than the other, making the underlying water ice evaporate and redeposit on the other side. This in turn reinforces the cycle…a positive feedback loop.
I know I said in my previous post that the Solar System is not a vortex (and it’s not) but that doesn’t mean there are no vortexes in the Solar System—in fact, thanks to the churning atmospheres of the gas giants, it’s full of them! And that’s no better demonstrated than at the poles of Saturn, where giant hurricane-like storms spin away year after year, powered by atmospheric convection and the rapid rotation of the planet.
I’ve often posted about the vortex at the north pole of Saturn—and yes it’s quite impressive—but there’s also a similar feature at Saturn’s south pole as well, albeit a bit more subtle and much less turbulent. The image above is a color view, made from raw data acquired in red, green, blue, and polarized light by NASA’s Cassini spacecraft on July 15, 2008. That was a just over a year before Saturn’s spring equinox and the planet’s south pole was moving into shadow, but still had enough illumination for Cassini to capture some images.
Check out a more direct view down into the vortex below:
NASA’s Cassini spacecraft captured these images of a propeller in Saturn’s A ring on Feb. 21, 2017. These are the sharpest images ever taken of a propeller and reveal an unprecedented level of detail. This propeller is nicknamed “Santos-Dumont” after the Brazilian-French aviator who is hailed as the father of aviation in Brazil.
The February 2017 imaging was Cassini’s first targeted observation of a propeller. The two views show the same object from opposite sides of the rings. The top image looks toward the rings’ sunlit side, while the bottom image shows the unilluminated side, where sunlight filters through the backlit ring.
Propellers are the term given to small disturbances in Saturn’s rings caused by the gravitational influence of embedded moonlets. They are thematically nicknamed in honor of famous world aviators. The particularly large propeller Santos-Dumont is caused by an object a little over half a mile (1 km) across.
More than just being ring decorations, propellers are important to researchers because they mimic the behavior of objects in an orbiting debris field; they are sort of like miniature protoplanets inside a circumstellar disk. They were first spotted by Cassini in July 2004.
“Observing the motions of these disk-embedded objects provides a rare opportunity to gauge how the planets grew from, and interacted with, the disk of material surrounding the early sun,” said Cassini imaging team leader Carolyn Porco in 2010. “It allows us a glimpse into how the solar system ended up looking the way it does.”
Read the rest of this story here: Cassini Targets a Propeller in Saturn’s A Ring
A field of spike-like structures rise up over two miles from the outer edge of Saturn’s B ring in the amazing image above, captured by Cassini during Saturn’s spring equinox in August 2009. These pointy perturbations are caused by the gravitational nudges of tiny (~1/2 mile) embedded moonlets traveling around Saturn within the B ring, causing fine icy particles to “splash” upwards from the otherwise relatively flat ring when they pass by them. The moonlets themselves are held in their orbits by the gravity of Mimas.
The spikes were made visible mainly because of the angle of illumination at the time of equinox, which on Saturn occurs every 15 years and in this instance was on Aug. 11, 2009.