After six years of up-close observations, the Cassini space mission is painting the most detailed picture ever of Saturn and its complex ring system.
One of the most remarkable images of Saturn that the Cassini spacecraft has captured is the sweep of the rings from the unlit side—a view not visible from Earth. The central B ring is dense enough that sunlight doesn’t penetrate to the northern regions of the planet, making it appear darker than the other rings. Sunlight filters easily through the lower- density rings. | Image courtesy of NASA/JPL/CICLOPS
Data returned by the robotic spacecraft—and explored in this week’s issue of Science—have shown that the rings, shaped by vigorous evolutionary processes, are tumultuous and constantly changing, a finding that lends some support to the theory that Saturn’s rings are quite young compared to the solar system. Cassini is also informing scientists about the planet’s atmosphere, ionosphere, and magnetosphere, making it clear that they are distinct from those of other planets.
This week in Science, two Review articles explore this new Cassini data. In one, Jeffrey Cuzzi from NASA and colleagues from around the world put a spotlight on Saturn’s ring system, which is the most complex and extensive in the solar system.
“The ongoing evolution suggests that Saturn’s rings, or parts thereof, might be only one-tenth the solar system’s age… ,” Cuzzi writes. “An emerging perspective, after almost six years of study, is that Saturn’s rings show dramatic variability on much shorter time scales—decades, years, even weeks.”
Cuzzi and his colleagues also say that many of the processes affecting Saturn’s rings can be observed in proto-planetary disks—the precursors to new planets.
The rings are made mostly of water ice and organized into multiple layers, each one unique. Based on Cassini’s near-infrared observations, Cuzzi and his research team suggest that a mysterious reddish coloration, which contaminates portions of those layers, could be attributed to small clusters of carbon rings or by negatively charged iron compounds.
In a separate Review, Tamas Gombosi from the University of Michigan and Andrew Ingersoll from the California Institute of Technology turn their attention to Saturn’s atmosphere, ionosphere, and magnetosphere.
Using the tools on-board Cassini, these researchers analyzed the wind speeds and jet streams influencing the planet’s atmosphere, and listened in on lightning storms rocking the planet’s face.
They describe Saturn’s magnetosphere, which forms around planets when solar winds interact with a planet’s magnetic field, as a distinctive hybrid between Jupiter’s and Earth’s, unlike any other planet’s in the solar system.
“There are two types of magnetospheres, those like Jupiter and those like Earth. Saturn is in between,” Gombosi writes in the Review. “Cassini showed that Saturn’s magnetodisk is bowl-shaped and bent above the equator, whereas Saturn’s magnetic south pole was tilted toward the Sun. This is different from Jupiter, where the magnetodisk warps downward, and from Earth, where the magnetodisk is absent.”
The Cassini space mission is a cooperative effort by NASA, the European Space Agency, and the Italian Space Agency. After nearly a voyage of nearly seven years, Cassini reached the gaseous, ringed planet in 2004, and it has been collecting information ever since. With data from the ongoing mission, along with recent ground-based observations and old data from the Voyager missions, researchers are learning more than ever about Saturn, its many moons, and its ornate ring system.
Cassini will continue transmitting data from the ringed, seventh planet from the Sun back to researchers on Earth for years to come—and scientists will undoubtedly unlock many more secrets of Saturn in the years to come.