In 2005, the Cassini space probe orbited Saturn’s frozen moon Enceladus to photograph “enormous jets of water ice and vapor emanating from four parallel slashes near its south pole,” reports Science. “Since then, researchers have detected organic molecules and hydrogen in the jets — potential food for microbes — making Enceladus one of the top destinations in the search for life elsewhere in the Solar System.”
But a new paper posted this week on the preprint server arXiv claims to finally understand the mystery of that moon’s “tiger stripes”:
The stripes…are 130 kilometers long and are spaced roughly 35 kilometers apart — rather large features on a moon only 500 kilometers in diameter. Nobody quite understood their origin, or why they were only seen at one pole…
As it orbits around Saturn, Enceladus experiences gravitational tidal forces that squeeze and heat it. Cassini data had already shown that a liquid water ocean sits underneath the outer ice shell, which is thinnest at the north and south poles. According to the new study, led by Douglas Hemingway of the Carnegie Institution for Science in Washington, D.C., as the moon cooled over time and some of the ocean water refroze, the new ice generated strain that built up in the surface until it broke. “It’s like your pipes freezing on a cold day,” says planetary scientist Francis Nimmo of the University of California, Santa Cruz, who was not involved in the study… That first fissure, extending down to the ocean, allowed a geyser to spray snow on its two flanks. The weight of this extra material produced more strains. In their study, the researchers calculate that these forces should have cracked additional grooves on either side, roughly 35 kilometers from the original one…
The moon’s low gravity means that fractures can bust all the way through its outer shell and persist. On a more massive moon, the researchers say in their study, the weight of heavier ice would tend to squeeze cracks shut.
of this story at Slashdot.
Source:: Slashdot