Our solar system is fantastically bizarre. There are worlds with features we never imagined. Storms larger than planets, moons with under-surface oceans, lakes of methane, worldlets that swap places…and that’s just at Saturn.
Images taken during the Cassini spacecraft’s orbital insertion on June 30 show definite compositional variation within the rings. This image shows, from left to right, the outer portion of the C ring and inner portion of the B ring. The B ring begins a little more than halfway across the image. The general pattern is from “dirty” particles indicated by red to cleaner ice particles shown in turquoise in the outer parts of the rings.
The Cassini spacecraft once again dons its special infrared glasses to peer through Titan’s haze and monitor its surface. Here, Cassini has recaptured the equatorial region dubbed “Senkyo.” The dark features are believed to be vast dunes of hydrocarbon particles that precipitated out of Titan’s atmosphere.
Move over exoplanets, exomoons may harbour life too
In the Star Wars universe, everyone’s favourite furry aliens, the Ewoks, famously lived on the “forest moon of Endor”. In scientific terms, the Ewok’s home world would be referred to as an exomoon, which is simply a moon that orbits an exoplanet – any planet that orbits a star other than our sun.
Although more than 1,000 exoplanets have been discovered since the first one was found in 1995, only a handful of those are thought to be habitable, at least by life as we know it. New research shows that exomoons, too, could provide habitable environments. Although we are yet to find exomoons, we have good reasons to believe that there should be many, even more than exoplanets.
In this, our 10th Christmas offering from across the hundreds of millions of miles that lie between us and Saturn, you will find some of the most splendid and fascinating sights this historic exploration of the ringed planet has uncovered: the hexagonally-shaped jet stream encircling the pole in Saturn’s northern hemisphere, the graceful shadows of its rings arcing across its south, the northern lakes and seas of liquid organics hidden under the hazy atmosphere of Titan, the brilliant ball of glittering ice that is the small active world of Enceladus, and more.
Spend a moment or two and revel in the marvels that our travels in this far-flung planetary system have brought. What wonders we have had for a decade to behold.
Best wishes to all of you, and stay warm, safe, and happy!
Saturn’s largest and second largest moons, Titan and Rhea, appear to be stacked on top of each other in this true-color scene from NASA’s Cassini spacecraft. The north polar hood can be seen on Titan (3,200 miles or 5,150 kilometers across) appearing as a detached layer at the top of the moon on the top right.
NASA’s Cassini spacecraft has capped 2013 with a spectacular new collection of Saturn photos showcasing the planet’s beauty, as well with its trademark rings and strange moons.
The newly released Saturn photos by Cassini include two views of Enceladus, Saturn’s sixth-largest moon. Enceladus is a winter-appropriate ice world. Geysers at its poles shoot ice particles into space, some of which make it into orbit around Saturn. Some of this space “snow” becomes part of Saturn’s E ring, Saturn’s second outermost ring that is made of microscopic particles.
Other images highlight Saturn’s largest moon, Titan. There are no jolly elves at Titan’s north pole; liquid methane and ethane seas appear as splotchy features near the moon’s poles. At the south pole, a high-altitude vortex swirls. The hazy orange atmosphere of Titan is thought to resemble the atmosphere of early Earth.
PASADENA, Calif. — The intensity of the jets of water ice and organic particles that shoot out from Saturn’s moon Enceladus depends on the moon’s proximity to the ringed planet, according to data obtained by NASA’s Cassini spacecraft.
The finding adds to evidence that a liquid water reservoir or ocean lurks under the icy surface of the moon. This is the first clear observation the bright plume emanating from Enceladus’ south pole varies predictably. The findings are detailed in a scientific paper in this week’s edition of Nature.
"The jets of Enceladus apparently work like adjustable garden hose nozzles," said Matt Hedman, the paper’s lead author and a Cassini team scientist based at Cornell University in Ithaca, N.Y. "The nozzles are almost closed when Enceladus is closer to Saturn and are most open when the moon is farthest away. We think this has to do with how Saturn squeezes and releases the moon with its gravity."
Cassini, which has been orbiting Saturn since 2004, discovered the jets that form the plume in 2005. The water ice and organic particles spray out from several narrow fissures nicknamed “tiger stripes.”
"The way the jets react so responsively to changing stresses on Enceladus suggests they have their origins in a large body of liquid water," said Christophe Sotin, a co-author and Cassini team member at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. "Liquid water was key to the development of life on Earth, so these discoveries whet the appetite to know whether life exists everywhere water is present."
For years scientists hypothesized the intensity of the jets likely varied over time, but no one had been able to show they changed in a recognizable pattern. Hedman and colleagues were able to see the changes by examining infrared data of the plume as a whole, obtained by Cassini’s visual and infrared mapping spectrometer (VIMS), and looking at data gathered over a long period of time.
The VIMS instrument, which enables the analysis of a wide range of data including the hydrocarbon composition of the surface of another Saturnian moon, Titan, and the seismological signs of Saturn’s vibrations in its rings, collected more than 200 images of the Enceladus plume from 2005 to 2012. These data show the plume was dimmest when the moon was at the closest point in its orbit to Saturn. The plume gradually brightened until Enceladus was at the most distant point, where it was three to four times brighter than the dimmest detection. This is comparable to moving from a dim hallway into a brightly lit office.
Adding the brightness data to previous models of how Saturn squeezes Enceladus, the scientists deduced the stronger gravitational squeeze near the planet reduces the opening of the tiger stripes and the amount of material spraying out. They think the relaxing of Saturn’s gravity farther away from planet allows the tiger stripes to be more open and for the spray to escape in larger quantities.
"Cassini’s time at Saturn has shown us how active and kaleidoscopic this planet, its rings and its moons are," said Linda Spilker, Cassini project scientist at JPL. "We’ve come a long way from the placid-looking Saturn that Galileo first spied through his telescope. We hope to learn more about the forces at work here as a microcosm for how our solar system formed."
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology, Pasadena, manages the mission for NASA’s Science Mission Directorate in Washington. The VIMS team is based at the University of Arizona in Tucson.