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Saturn's tiny, frozen moon Enceladus is a strange place. Just 300 miles across, the moon is thought to have an outer shell of ice covering a global ocean 20 miles deep, encasing a rocky core. Slashed across Enceladus' south pole are four straight, parallel fissures or "tiger stripes" from which water erupts. These fissures aren't quite like anything else in the solar system.

"We want to know why the eruptions are located at the south pole as opposed to some other place on Enceladus, how these eruptions can be sustained over long periods of time and finally why these eruptions are emanating from regularly spaced cracks," said Max Rudolph, assistant professor of earth and planetary sciences at the University of California, Davis.

[...] Enceladus' 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. Yet the south polar fissures remain open, and in fact reach all the way to the liquid ocean below. 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. That stops the crack from freezing shut.

The release of pressure from the fissures stops new cracks from forming elsewhere on the moon, such as at the north pole. 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. That causes the ice sheet to flex, the researchers calculate, just enough to set off a parallel crack about 20 miles away. "Our model explains the regular spacing of the cracks," Rudolph said.

Title		Tidal Forces Explain "Tiger Stripes" on Enceladus
Date		Thursday December 12 2019, @04:23AM
Author		martyb
Topic
from the wise-crack dept.

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