![]() "We're predicting which bits of the tiger stripes are going to be hottest." "The amount of backwards and forwards motions you get depends on the direction the tiger stripes are pointing in, so different areas of the tiger stripes ought to have different motions and different temperatures," he said. And Nimmo's team predicts that some portions of the tiger stripes should be more active than others. For example, tidal heating should only cause the tiger stripes to open at certain times during the moon's orbit around Saturn. "The thing that's driving everything is the that are opening and closing the cracks and moving the faults backwards and forwards," Nimmo said.īoth ideas could be confirmed with further observations by Cassini or other spacecraft. This phenomenon, called " tidal heating," could drive the opening and closing of the tiger stripes and also cause the ice sheets to flex and grind against each other, the researchers speculate. Like a repeatedly bent paperclip, the constant motion on Enceladus generates friction and heat. When Enceladus is closest to Saturn, gravity causes a bulge to form on the side of the moon facing the planet the bulge shrinks as the moon moves farther away. Because its orbit around Saturn is elliptical, the moon is closer to Saturn at some points of its orbit than others and the force of gravity it feels from the planet varies with distance. "There's two different things going on and they're happening simultaneously," Hurford said in a telephone interview.īoth teams think their mechanisms are driven by Saturn's uneven gravitational pull on Enceladus as it revolves around the planet. The researchers say their two mechanisms complement each other. "If the two sides of the fault rub backwards and forwards against each other, you generate heat, just like you get heating if you rub your hands together," Nimmo told .Īnother model, created by researchers led by Terry Hurford of the NASA Goddard Space Flight Center, suggests the tiger stripes might also open and close periodically, like enormous valves, to allow volatile material trapped beneath the ice to escape to the surface. The melted ice would sublimate into water vapor and float directly into space. Funding was also provided by NASA and the National Science Foundation.Using computer models, researchers led by Francis Nimmo of the University of California, Santa Cruz found that ice sheets grinding against each other at tiger stripe fractures generate enough heat to melt some of the ice. The work was based on data collected by the NASA/ESA Cassini mission to Saturn. ![]() Rudolph and Michael Manga, 9 December 2019, Nature Astronomy. Reference: “Cascading parallel fractures on Enceladus” by Douglas J. “Our model explains the regular spacing of the cracks,” Rudolph said.įor more on this study, see Water Erupts Through Fissures on Enceladus’ Icy Surface. That causes the ice sheet to flex, the researchers calculate, just enough to set off a parallel crack about 20 miles away. But at the same time, water vented from the crack falls back as ice, building up the edges of the fissure and weighing it down a bit. The release of pressure from the fissures stops new cracks from forming elsewhere on the moon, such as at the north pole. That’s because liquid water within the fissure is sloshed around by tidal forces produced by Saturn’s gravity, releasing energy as heat, Rudolph said. Yet the south polar fissures remain open, and in fact reach all the way to the liquid ocean below. ![]() ![]() As liquid water solidifies into ice under the outer ice shell, it expands in volume, putting pressure on the ice until it cracks.Įnceladus’ surface temperature is about negative 200 degrees Celsius, so if a crack formed in the ice, you would expect it to freeze shut pretty quickly. Saturn’s gravity exerts tidal forces on Enceladus, which causes the heating and cooling of the tiny world. ![]()
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