Saturn Spectacular: A Moon With Fizzy Oceans, Ring Tsunamis, and More
Carbonated oceans, moons torn apart, ring tsunamis—there’s a flurry of cool news about Saturn coming out of the American Astronomical Society’s Division for Planetary Science meeting in Pasadena, California.
The fizzy ocean of Enceladus
Saturn’s moon Enceladus is one of the prime candidates for some kind of life elsewhere in the solar system, thanks the the possibility that a large subsurface ocean feeds the plumes of ice and vapor that the Cassini spacecraft has spied blasting forth from the moon. At the AAS meeting in California, Cassini scientists Dennis Matson proposed something new about this extraterrestrial ocean: It could be carbonated.
Noncarbonated seawater circulating from the moon’s solid core to the surface would stall rather than seep though cracks in the ice because seawater is denser than the icy carapace. If the seawater were fizzy, however, gas bubbles would form in the liquid, reducing the ocean’s density. Once the seawater became less dense than the ice, the water could rise to within 10 to 15 meters of the frigid surface. That’s close enough to fill chambers in the icy crust with water that feeds the south polar plumes. [Science News]
Saturn’s mighty rings formed from a moon’s destruction?
The majestic rings are what people know best about the sixth planet, but astronomers still are not sure just how they formed. From a small moon that broke apart, or perhaps a comet?
Both ideas have a problem—the rings of Saturn are nearly all water ice. Either a comet or a smaller moon would have caused more rock in the rings. So Robin Canup of the Southwest Research Institute is pushing a different idea: a giant moon hitting the planet could have created the icy rings.
Canup’s hypothesis is that the rings were formed when a Titan-sized moon with a rocky core and an icy mantle spiralled into Saturn early in solar system history. Tidal forces ripped off part of the icy mantle, distributing it into what would become the rings. But the rocky core was made of tougher stuff. “It hits the planet’s surface before it disrupts,” she said. “The end result is a pure ice ring.” [Nature]
You can check out the abstract to her presentation online.
Titan creates ring tsunamis
Speaking of the rings, they are not so uniform as they appear in the snazzy images we might have as computer desktops. There are gaps aplenty, and Voyager 1 one spotted one of the most curious ones when it made a flyby in the 1980s. According to Cassini’s newer observations, the gap is only about a third of a mile across, but it rises 2 miles above the ring plane. Cassini scientists describe the effect as resembling a tsunami propagating across the rings, and they’ve pinpointed its source: Titan, the largest moon of Saturn.
The ring’s corrugation comes from a gravitational relationship with Titan, whose orbit around Saturn falls at a slight angle to the ring plane. At a certain point in its orbit, Titan yanks the ring particles upward, starting a wave that travels around the ring. “The whole pattern rotates around at the same rate as the satellite Titan orbits Saturn, once every 16 days,” [Phillip] Nicholson said. The wave rolling along under Cassini occasionally blocked the spacecraft’s view. “That accounts for the fact that the gap seems to come and go,” he added. [Wired.com]